Navajo Nation v. Department of the Interior, et al

Filing

FILED OPINION (RONALD M. GOULD, MARSHA S. BERZON and MARVIN J. GARBIS) AFFIRMED IN PART, REVERSED IN PART AND REMANDED. Judge: MSB Authoring FILED AND ENTERED JUDGMENT. [10675851]

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TABLE OF CONTENTS
S.1 INTRODUCTION AND BACKGROUND.........................................................................1
S.1.1

INTRODUCTION ................................................................................................. 1

S.1.2

PROPOSED FEDERAL ACTION ........................................................................ 4

S.1.3
S.1.3.1
S.1.3.2

BACKGROUND ................................................................................................... 4
Long-Range Operating Criteria ................................................................ 5
Annual Operating Plan .............................................................................6

S.1.4

PURPOSE AND NEED FOR ACTION................................................................ 7

S.1.5

RELATIONSHIP TO UNITED STATES–MEXICO WATER TREATY ........... 8

S.1.6
RELATED AND ONGOING ACTIONS.............................................................. 8
S.1.6.1
California’s Colorado River Water Use Plan ........................................... 8
S.1.6.1.1
Imperial Irrigation District/San Diego County Water Authority
Water Transfer.......................................................................................... 9
S.1.6.1.2
All-American and Coachella Canal Lining Projects .............................. 10
S.1.6.2
Glen Canyon Dam Operations................................................................10
ior
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S.1.6.2.1
Adaptive Management Program............................................................. 11
the
t. of r 29, 20
pand Beach/Habitat-Maintenance
S.1.6.2.2
Beach/Habitat-Building Flows
. De
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Flows ...................................................................................................... 11
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S.1.6.2.3
Temperature Control at Glen Canyon Dam............................................ 12
NavRelated hivedBiological and Conference Opinion on
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arc to the
S.1.6.3
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8Colorado River Operations and Maintenance ............................. 12
Lower
-16
o. 14
N
S.1.6.4
Lower Colorado River Multi-Species Conservation Program ............... 13
S.1.6.5
Secretarial Implementation Agreement Related to California’s
Colorado River Water Use Plan ............................................................. 13
S.1.6.6
Offstream Storage of Colorado River Water and Development and
Release of Intentionally Created Unused Apportionment in the
Lower Division States ............................................................................ 14
S.2 ALTERNATIVES .............................................................................................................. 14
S.2.1
S.2.1.1
S.2.1.2

DEVELOPMENT OF ALTERNATIVES ........................................................... 14
Origins of California, Six States and Basin States Alternatives............. 14
Utilization of Proposals from Basin States............................................. 15

S.2.2
DESCRIPTION OF ALTERNATIVES............................................................... 16
S.2.2.1
No Action Alternative and Baseline Conditions ....................................16
S.2.2.1.1
Approach to Surplus Water Determination ............................................ 16
S.2.2.1.2
70R Baseline Surplus Triggers ............................................................... 16
S.2.2.2
Basin States Alternative (Preferred Alternative) ....................................17
S.2.2.2.1
Approach to Surplus Water Determination ............................................ 17
S.2.2.2.2
Basin States Alternative Surplus Triggers..............................................18

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S.2.2.3
S.2.2.3.1
S.2.2.3.2
S.2.2.4
S.2.2.4.1
S.2.2.4.2
S.2.2.5
S.2.2.5.1
S.2.2.5.2
S.2.2.6
S.2.2.6.1
S.2.2.6.2

Flood Control Alternative....................................................................... 18
Approach to Surplus Water Determination ............................................ 18
Flood Control Alternative Surplus Triggers........................................... 18
Six States Alternative ............................................................................. 18
Approach to Surplus Water Determination ............................................ 18
Six States Alternative Surplus Triggers.................................................. 19
California Alternative .............................................................................19
Approach to Surplus Water Determination ............................................ 19
California Alternative Surplus Triggers ................................................. 19
Shortage Protection Alternative.............................................................. 20
Approach to Surplus Water Determination ............................................ 20
Shortage Protection Alternative Surplus Triggers.................................. 20

S.3 SUMMARY OF ENVIRONMENTAL CONSEQUENCES .............................................20
S.3.1

USE OF MODELING TO IDENTIFY POTENTIAL FUTURE
COLORADO RIVER
System Conditions.................................................................................. 20

S.3.2

BASELINE CONDITIONS................................................................................. 20

S.3.3

IMPACT DETERMINATION APPROACH ......................................................21
erior

S.3.4
S.3.5
S.3.6

e Int
Dep mber 2
POTENTIALLY AFFECTED AREA ................................................................. 21
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ajoSURPLUS ALTERNATIVES TO BASELINE
COMPARISONvOF
Na
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, arc
CONDITIONS 64
cite 168
Effects on Reservoir Surface Elevations and River Flows.....................22
14No. Summary of Environmental Impacts...................................................... 24

17
th
PERIOD OF ANALYSIS ....................................................................................21
t. of
9, 20

S.3.6.1
S.3.6.2
S.3.6.3
S.3.6.3.1
S.3.6.3.2
S.3.6.3.3
S.3.6.3.4
S.3.6.3.5
S.3.6.3.6
S.3.6.3.7

Environmental Commitments.................................................................24
Water Quality ......................................................................................... 25
Riverflow Issues .....................................................................................25
Aquatic Resources ..................................................................................25
Special-Status Species ............................................................................26
Recreation............................................................................................... 26
Cultural Resources..................................................................................26
Transboundary Impacts ..........................................................................26

S.4 OTHER NEPA CONSIDERATIONS................................................................................ 27
S.4.1

CUMULATIVE IMPACTS................................................................................. 27

S.4.2

RELATIONSHIP BETWEEN SHORT-TERM USES OF THE
ENVIRONMENT AND
Long-Term Productivity......................................................................... 28

S.4.3

IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF
RESOURCES ...................................................................................................... 28

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

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TABLE OF CONTENTS

S.5 CONSULTATION AND COORDINATION....................................................................29
S.5.1
S.5.1.1
S.5.1.2

GENERAL PUBLIC INVOLVEMENT ACTIVITIES....................................... 29
Project Scoping....................................................................................... 29
Public Review of DEIS .......................................................................... 30

S.5.2
S.5.2.1
S.5.2.2

FEDERAL AGENCY COORDINATION .......................................................... 31
National Park Service ............................................................................. 31
U.S. Section of the International Boundary and Water
Commission............................................................................................ 31
U.S. Bureau of Indian Affairs................................................................. 31
U.S. Fish and Wildlife Service Including Endangered Species Act
Compliance............................................................................................. 31
National Marine Fisheries Service ......................................................... 33
National Historic Preservation Act Compliance ....................................33

S.5.2.3
S.5.2.4
S.5.2.5
S.5.2.6
S.5.3

TRIBAL CONSULTATION ...............................................................................34

S.5.4

STATE AND LOCAL WATER AND POWER AGENCIES
COORDINATION ............................................................................................... 34

S.5.5

NON-GOVERNMENTAL ORGANIZATIONS COORDINATION .................35

S.5.6
S.5.7
S.5.8

erior
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SUMMARY OF COORDINATION ep
CONTACTS .............................................36
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FEDERAL REGISTER NOTICES .......................................................................36
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MEXICO CONSULTATION .............................................................................. 36
17
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EXECUTIVE SUMMARY
COLORADO RIVER INTERIM SURPLUS CRITERIA
FINAL ENVIRONMENTAL IMPACT STATEMENT
S.1

INTRODUCTION AND BACKGROUND

S.1.1 INTRODUCTION
The Secretary of the United States Department of the Interior (Secretary), acting
through the United States Bureau of Reclamation (Reclamation), is considering the
adoption of specific interim criteria under which surplus water conditions may be
declared in the lower Colorado River Basin (see Map S-1) during a 15-year period that
would extend through 2016.
The Secretary is vested with the responsibility of managing the mainstream waters of
the lower Colorado River pursuant to applicable federal law. This responsibility is
carried out consistent with a collection of documents known as the Law of the River,
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which includes a combination of federal and state statutes, interstate compacts, court
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decisions and decrees, an international treaty, contracts of the Secretary, operating
with the
20
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criteria, regulations and administrative decisions.
v. D
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ajo management objectives are to:
The long-term Colorado River systemhive
Nav
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cite
8
• Minimize 14-16
. flood damages from river flows;
No
•

Release water only in accordance with the 1964 Decree in Arizona v.
California (Decree);

•

Protect and enhance the environmental resources of the basin;

•

Provide reliable delivery of water for beneficial consumptive use;

•

Increase flexibility of water deliveries under a complex allocation system;

•

Encourage efficient use of renewable water supplies;

•

Minimize curtailment to users who depend on such supplies; and

•

Consider power generation needs.

As the agency that is designated to act on the Secretary’s behalf with respect to these
matters, Reclamation is the Lead Federal Agency for the purposes of National
Environmental Policy Act of 1969 (NEPA) compliance for the development and
implementation of the proposed interim surplus criteria. The National Park Service
(NPS) and the United States Section of the International Boundary and Water

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EXECUTIVE SUMMARY

Commission (USIBWC) are cooperating agencies for purposes of assisting with the
environmental analysis.

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EXECUTIVE SUMMARY

Map S-1 Colorado River Drainage Basin

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EXECUTIVE SUMMARY

A Final Environmental Impact Statement (FEIS), of which this document is a summary,
has been prepared pursuant to NEPA, as amended, and the Council on Environmental
Quality (CEQ) Regulations for Implementing the Procedural Provisions of NEPA (40
Code of Federal Regulations [CFR] Parts 1500 through 1508). The FEIS has been
prepared to address the formulation and evaluation of specific interim surplus criteria
and to identify the potential environmental effects of implementing such criteria.
The FEIS addresses the environmental issues associated with, and analyzes the
environmental consequences of, various alternatives for specific interim surplus criteria.
The alternatives addressed in the FEIS are those Reclamation has determined would
meet the purpose and need for the federal action and represent a broad range of the most
reasonable alternatives.
In addition to this Summary, the FEIS contains three separate volumes. Volume I
describes the proposed action, the alternatives considered, the analysis of potential
effects of interim surplus criteria on Colorado River operation and associated resources,
and environmental commitments associated with the action alternatives. Volume II
contains attachments that are comprised of documents and other supporting material
that provide detailed historical background and/or technical information concerning this
proposed action. Volume III contains reproductions of comment letters from the public
resulting from the public review of the Draft Environmental Impacterior
t Statement (DEIS)
he In 2017
and Reclamation’s responses to the comments received.of t
,

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S.1.2 PROPOSED FEDERAL ACTION
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The proposed federal action is 4, arch
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cite the 68
to Article III(3)(b) of 4-1Criteria for Coordinated Long-Range Operation of the
1
Colorado River Reservoirs Pursuant to the Colorado River Basin Project Act of
No.

September 30, 1968 (Long-Range Operating Criteria [LROC]). The interim surplus
criteria would be used annually to determine the conditions under which the Secretary
may declare the availability of surplus water for use within the states of Arizona,
California and Nevada. The criteria must be consistent with both the Decree entered by
the United States Supreme Court in 1964 in the case of Arizona v. California and the
LROC. The interim surplus criteria would remain in effect for determinations made
through calendar year 2015 regarding the availability of surplus water through calendar
year 2016, subject to five-year reviews conducted concurrently with LROC reviews,
and would be applied each year as part of the Annual Operating Plan (AOP).
S.1.3 BACKGROUND
Pursuant to Article II(B)2 of the Decree, if there exists sufficient water available in a
single year for pumping or release from Lake Mead to satisfy annual consumptive use
in the states of California, Nevada and Arizona in excess of 7.5 million acre-feet (maf),
such water may be determined by the Secretary to be available as surplus water. The
Secretary is authorized to determine the conditions upon which such water may be
made available. The Colorado River Basin Project Act of 1968 (CRBPA) directs the

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EXECUTIVE SUMMARY

Secretary to adopt criteria for coordinated long-range operation of reservoirs on the
Colorado River in order to comply with and carry out the provisions of the Colorado
River Compact of 1922 (Compact), the Colorado River Storage Project Act of 1956
(CRSPA), the Boulder Canyon Project Act of 1928 (BCPA) and the United
States-Mexico Water Treaty of 1944 (Treaty). These criteria are the LROC, discussed
further below. The Secretary sponsors a formal review of the LROC every five years.
The LROC provide that the Secretary will determine the extent to which the reasonable
consumptive use requirements of mainstream users in Arizona, California and Nevada
(the Lower Division states) can be met. The LROC define a normal year as a year in
which annual pumping and release from Lake Mead will be sufficient to satisfy 7.5 maf
of consumptive use in accordance with the Decree. A surplus year is defined as a year
in which water in quantities greater than normal (i.e., greater than 7.5 maf) is available
for pumping or release from Lake Mead pursuant to Article II(B)2 of the Decree after
consideration of relevant factors, including the factors listed in the LROC. Surplus
water is available to agencies which have contracted with the Secretary for delivery of
surplus water, for use when their water demand exceeds their basic entitlement, and
when the excess demand cannot be met within the basic apportionment of their state.
Water apportioned to, but unused by one or more Lower Division states can be used to
satisfy beneficial consumptive use requests of mainstream users in other Lower
r
Division states as provided in Article II(B)(6) of the Decree. Interio

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Pursuant to the CRBPA, the LROC are utilized De
. by the
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make determinations with respect to the projected plan of operations of the storage
Nat
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reservoirs in the Colorado RiverjBasin. ivedAOP is prepared by Reclamation, acting on
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behalf of the Secretary, in consultation with representatives of the Colorado River Basin
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states (Basin States)14-1
and other parties, as required by federal law. The interim surplus
No. to implement the provisions of Article III(3)(b) of the LROC on an
criteria would serve
annual basis in the determinations made by the Secretary as part of the AOP process.
S.1.3.1

LONG-RANGE OPERATING CRITERIA

The CRBPA required the Secretary to adopt operating criteria for the Colorado River by
January 1, 1970. The LROC, adopted in 1970, control the operation of the Colorado
River reservoirs in compliance with requirements set forth in the Compact, the CRSPA,
the BCPA, the Treaty and other applicable federal laws. Under the LROC, the
Secretary makes annual determinations in the AOP (discussed in the following section)
regarding the availability of Colorado River water for deliveries to the Lower Division
states (Arizona, California and Nevada). A requirement to equalize the active storage
between Lake Powell and Lake Mead when there is sufficient storage in the Upper
Basin is also included in Section 602(a) of the LROC, as required by the CRBPA.
Section 602 of the CRBPA, as amended, provides that the LROC can only be modified
after correspondence with the governors of the seven Basin States and appropriate
consultation with such state representatives as each governor may designate. The
LROC call for formal reviews at least every five years. The reviews are conducted as a

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EXECUTIVE SUMMARY

public involvement process and are attended by representatives of federal agencies, the
seven Basin States, Indian Tribes, the general public including representatives of the
academic and scientific communities, environmental organizations, the recreation
industry and contractors for the purchase of federal power produced at Glen Canyon
Dam. Past reviews have not resulted in any changes to the criteria.
S.1.3.2

ANNUAL OPERATING PLAN

The CRBPA requires preparation of an AOP for the Colorado River reservoirs that
guides the operation of the system for the water year. The AOP describes how
Reclamation will manage the reservoirs over a 12-month period, consistent with the
LROC and the Decree. The AOP is prepared annually by Reclamation in cooperation
with the Basin States, other federal agencies, Indian Tribes, state and local agencies and
the general public, including governmental interests as required by federal law.
As part of the AOP process, the Secretary makes annual determinations regarding the
availability of Colorado River water for deliveries to the Lower Division states as
described below. The Secretary is required to determine when normal, surplus or
shortage conditions occur in the lower Colorado River, based on various factors
including storage and hydrologic conditions in the Colorado River Basin.

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Normal conditions exist when the Secretary determines thathe
sufficient 017
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is available to satisfy 7.5 maf of annual consumptive t. in therLower Division states.
. De
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If a state will not use all of its apportionedn v for ovem the Secretary may allow
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other states of the Lower Division to usevthe unused apportionment, provided that the
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14Surplus conditions exist when the Secretary determines that sufficient mainstream water
No.
is available for release to satisfy consumptive use in the Lower Division states in excess
of 7.5 maf annually. This excess consumptive use is surplus and is distributed for use in
California, Arizona and Nevada in allocations of 50, 46 and 4 percent, respectively. As
stated above, if a state will not use all of its apportioned water for the year, the
Secretary may allow other states of the Lower Division to use the unused
apportionment, provided that the use is covered under a contract with the consuming
entity. Surplus water under the Decree, for use in the Lower Division states, was made
available by the Secretary in calendar years 1996, 1997, 1998, 1999 and 2000.
Deliveries of surplus water to Mexico in accordance with the Treaty were made in
calendar years 1983-1988, 1997, 1998, 1999 and 2000.
Shortage conditions exist when the Secretary determines that insufficient mainstream
water is available to satisfy 7.5 maf of annual consumptive use in the Lower Division
states. When making a shortage determination, the Secretary must consult with various
parties, as set forth in the Decree and consider all relevant factors as specified in the
LROC (described above), including Treaty obligations, the priorities set forth in the
Decree and the reasonable consumptive use requirements of mainstream water users in

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the Lower Division. The Secretary is required to first provide for the satisfaction of the
presented perfected rights (PPRs) in the order of their priority, then to users who held
contracts on September 30, 1968 (up to 4.4 maf in California) and finally to users who
had contracted on September 30, 1968, when the CAP was authorized. To date, a
shortage has never been determined.
S.1.4 PURPOSE AND NEED FOR ACTION
To date, the Secretary has applied factors, including but not limited to those found in
Article III(3)(b)(i-iv) of the LROC, in annual determinations of the availability of
surplus quantities of water for pumping or release from Lake Mead. As a result of
actual operating experience and through preparation of AOPs, particularly during recent
years when there has been increasing demand for surplus water, the Secretary has
determined that there is a need for more specific surplus criteria, consistent with the
Decree and applicable federal law, to assist in the Secretary’s annual decision making
during an interim period.
For many years, California has been diverting more than its normal 4.4 maf
apportionment. Prior to 1996, California utilized unused apportionments of other
Lower Division states that were made available by the Secretary. Since 1996,
California has also utilized surplus water made available by Secretarial determination.
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California is in the process of developing the means to reducee annual use
f th its 20
pt. o full use 9, its apportionment
Colorado River water to 4.4 maf. Arizona is approaching ber 2 of
v. De v 2000.
and Nevada was expected to reach itsation
apportionment inem
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able to afford mainstream users
14California who currently utilize surplus flows, a greater degree of predictability with
No.
respect to the likely existence, or lack thereof, of surplus conditions on the river in a
given year. Adoption of the interim surplus criteria is intended to recognize
California’s plan to reduce reliance on surplus deliveries, to assist California in moving
toward its allocated share of Colorado River water and to avoid hindering such efforts.
Implementation of interim surplus criteria would take into account progress, or lack
thereof, in California’s efforts to achieve these objectives. The surplus criteria would
be used to identify the specific amount of surplus water which may be made available in
a given year, based upon factors such as the elevation of Lake Mead, during a period
within which demand for surplus Colorado River water will be reduced. The increased
level of predictability with respect to the prospective existence and quantity of surplus
water would assist in planning and operations by all entities that receive surplus
Colorado River water pursuant to contracts with the Secretary.
S.1.5 RELATIONSHIP TO UNITED STATES–MEXICO WATER TREATY
Under Article 10(a) of the Treaty, the United Mexican States (Mexico) is entitled to an
annual amount of 1.5 maf of Colorado River water. Under Article 10(b) of the Treaty,
Mexico may schedule up to an additional 0.2 maf when “there exists a surplus of waters

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of the Colorado River in excess of the amount necessary to satisfy uses in the United
States.” This is in addition to surplus determinations for the Lower Division states
made pursuant to Article II(2)(b) of the Decree and Article III(3)(B) of the LROC. The
proposed action is not intended to identify, or change in any manner, conditions when
Mexico may schedule this additional 0.2 maf. Under current practice, surplus
declarations under the Treaty for Mexico are declared when flood control releases are
made. Reclamation is currently engaged in discussions with Mexico through the IBWC
on the effects of the proposed action.
S.1.6 RELATED AND ON-GOING ACTIONS
A number of ongoing and new actions proposed by Reclamation and other entities are
related to the development of interim surplus criteria and the analysis contained in the
FEIS. This section describes these actions and their relationship to the development of
interim surplus criteria. The following actions have been described in environmental
documents, consultation packages under Section 7 of the Endangered Species Act
(ESA) or as project planning documents. Where appropriate, the FEIS incorporates by
reference information contained in these documents. The documents described below
are available for public inspection upon request at Reclamation offices in Boulder City,
Nevada; Salt Lake City, Utah; and Phoenix and Yuma, Arizona.

ior
Inter 17
S.1.6.1
CALIFORNIA’S COLORADO RIVER WATER USEthLAN
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California’s Colorado River Water Usetion v
a Plan (CA Plan),ewhich was formerly known as
Nov
the California 4.4 Plan or thevajo N callsd on
4.4 Plan, e for conservation measures to be put in place
i
in Nadependencyvon surplus Colorado River water. Surplus
that will reduce California’s 4, arch
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water is required to meet California’s current needs until implementation of the
-1
o. 14 can take place. During the period ending in 2016, the State of
conservation measures
N
California has indicated that it intends to reduce its reliance on Colorado River water to
meet its water needs above and beyond its 4.4-maf apportionment. It is important for
the long-term administration of the system to bring the Lower Basin uses into
accordance with the Lower Basin normal apportionment. In order to achieve its goals,
California has expressed a need to rely in some measure on the existence of surplus
Colorado River water through 2016. These interim surplus criteria could aid California
and its primary Colorado River water users as California reduces its consumptive use to
4.4 maf while ensuring that the other Basin States will not be placed at undue risk of
future shortages.
The CA Plan contains numerous water conservation projects, intrastate water exchanges
and groundwater storage programs. The CA Plan is related to the implementation of the
interim surplus criteria in the ways discussed below.
First, implementation of the CA Plan is necessary to ensure the Colorado River system
can meet the normal year deliveries in the Lower Basin over the long term. Failure of
California to comply with the CA Plan places at risk the objective of providing reliable
delivery of water for beneficial consumptive use to Lower Basin users. Therefore, the

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Secretary may condition the continuation of interim surplus criteria for the entire period
through 2016 on a showing of satisfactory progress in implementing the CA Plan.
Regardless of which alternative is ultimately selected, failure of California to carry out
the CA Plan may result in termination or suspended application of the proposed interim
surplus criteria. In that event, the Secretary would fashion appropriate surplus criteria
for the remaining period through 2016.
Second, from the perspective of the State of California, because of the linkage between
various elements of the CA Plan and the quantities of water involved, a reliable supply
of interim surplus water from the Colorado River is an indispensable pre-condition to
successful implementation of the CA Plan.
From the standpoint of environmental documentation and compliance, the CA Plan and
its various elements have been, or will be, addressed under separate federal and/or state
environmental reporting procedures.
S.1.6.1.1

Imperial Irrigation District/San Diego County Water Authority
Water Transfer

The Imperial Irrigation District (IID)/San Diego County Water Authority (SDCWA)
water transfer is one of the intrastate exchanges that is a part of the erior
CA Plan. SDCWA
Int water 7 the IID.
has negotiated an agreement for the long-term transfer of fconserved 01 from
the
pt. o water 2
Under the proposed contract, IID customers would undertakeer 29,conservation efforts
. De emb
to reduce their use of Colorado River ation v
water. Water conserved through these efforts
Nov
would be transferred to SDCWA. The agreement sets the primary transfer quantity at a
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maximum of 200tkaf/year. After arleast 10 years of primary transfers, an additional
d in 64, at ch
ci e 168
discretionary component not to exceed 100 kaf/year may be transferred to SDCWA, the
14Metropolitan Water District of Southern California (MWD) or Coachella Valley Water
No.
District (CVWD) in connection with the settlement of water rights disputes between IID
and these agencies. The initial transfer target date is 2002, or whenever the conditions
necessary for the agreement to be finalized are satisfied or waived, whichever is later.
This transfer is being addressed in an ongoing Environmental Impact Statement
(EIS)/Environmental Impact Report (EIR) and involves the change in point of delivery
of up to 300 kaf/year from Imperial Dam to Parker Dam.
S.1.6.1.2

All-American and Coachella Canal Lining Projects

Two other components of the CA Plan having effects on the river are the All-American
and Coachella Canal Lining Projects (the Coachella Canal is a branch of the AllAmerican Canal). These two similar actions involve the concrete lining of unlined
portions of the canals to conserve water presently being lost as seepage from the earthen
reaches. Together the projects involve a change in point of delivery of 93.7 kaf/year
from Imperial Dam for Parker Dam, 67.7 kaf/year for the All-American Canal and 26
kaf/year for the Coachella Canal. The effects of this change in point of delivery are
being addressed in the Secretarial Implementation Agreement Environmental
Assessment (EA) and Biological Assessment (BA). The Record of Decision (ROD) for

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the All-American Canal Lining Project was approved on July 29, 1994. Construction is
expected to begin in 2001. A draft EIS/EIR for the Coachella Canal Lining Project was
released on September 22, 2000 for public review.
S.1.6.2

GLEN CANYON DAM OPERATIONS

Glen Canyon Dam is operated consistent with the CRSPA and the LROC, which were
promulgated in compliance with Section 602 of the CRBPA. Glen Canyon Dam is also
operated consistent with the 1996 ROD on the Operation of Glen Canyon Dam FEIS
developed as directed under the Grand Canyon Protection Act of 1992.
The minimum release from Lake Powell, as specified in the LROC, is 8.23 maf per
year. The LROC require that, when Upper Basin storage is greater than the storage
required under Section 602(a) of the CRBPA, releases from Lake Powell will
periodically be governed by the objective to maintain, as nearly as practicable, active
storage in Lake Mead equal to the active storage in Lake Powell. Because of this
equalization provision in the LROC, changes in operations at Lake Mead will, in some
years, result in changes in annual release volumes from Lake Powell. It is through this
mechanism that delivery of surplus water from Lake Mead can influence the operation
of Glen Canyon Dam. Equalization is not required when there exists insufficient
r
storage in the Upper Basin, per Section 602(a) of the CRBPA.
terio

7
he In
. of t as29, 201 to
In acknowledgement that the operation of Glen Dept Dam, r authorized,
Canyon
.
mbe
maximize power production was havingion v
at a negative impact on downstream resources,
Nove
the Secretary determined inavajo N that an on should be prepared. The Operation
July 1989
ed EIS
in N 4, archivanalyzed alternative operation scenarios that
of Glen Canyon Dam EIS developed and
cited 1686
met statutory responsibilities for protecting downstream resources and achieving other
14authorized purposes, while protecting Native American interests. A final EIS was
No.
completed in March 1995 and the Secretary signed a ROD on October 8, 1996.
Reclamation also consulted with the United States Fish and Wildlife Service (Service)
under the ESA and incorporated the Service’s recommendations into the ROD.

The ROD describes criteria and plans for dam operations and includes other measures
to ensure Glen Canyon Dam is operated in a manner consistent with the Grand Canyon
Protection Act of 1992. Among these are an Adaptive Management Program, periodic
releases for beach/habitat-building flows (BHBFs), beach/habitat-maintenance flows
and further study of temperature control.
The ROD is based on the EIS, which contains descriptions and analyses of aquatic and
riparian habitats below Glen Canyon Dam, effects of Glen Canyon Dam release patterns
on the local ecology, cultural resources, sedimentation processes associated with the
maintenance of backwaters and sediment deposits along the river, Native American
interests, and relationships between release patterns and the value of hydroelectric
energy produced. Analyses of effects on other resources within the affected area are
also included. Additional information concerning the operation of Glen Canyon Dam is
contained in Section 3.3.

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S.1.6.2.1

Adaptive Management Program

The Adaptive Management Program provides a process for assessing the effects of
current operations of Glen Canyon Dam on downstream resources and using the results
to develop recommendations for modifying operating criteria and other resource
management actions. This is accomplished through the Adaptive Management Work
Group (AMWG), a federal Advisory Committee. The AMWG consists of stakeholders
that are federal and state resource management agencies, representatives of the seven
Basin States, Indian Tribes, hydroelectric power marketers, environmental and
conservation organizations and recreational and other interest groups. The duties of the
AMWG are in an advisory capacity only. Coupled with this advisory role are long-term
monitoring and research activities that provide a continual record of resource conditions
and new information to evaluate the effectiveness of the operational modifications.
S.1.6.2.2

Beach/Habitat-Building Flows and Beach/Habitat-Maintenance
Flows

BHBF releases are scheduled high releases of short duration that are in excess of power
plant capacity required for dam safety purposes and are made according to certain
specific criteria. These BHBFs are designed to rebuild high elevation sandbars, deposit
nutrients, restore backwater channels and provide some of the dynamicsrof a natural
terio
system. The first test of a BHBF was conducted in spring of 1996. 2017
he In
of t

9,
pt.
. De ateor near power plant capacity,
ber 2
Beach/habitat-maintenance flow releaseson v
are releases m
Nati beachn Nov conditions for recreation
which are intended to maintainajo
v favorable ed o and habitat
iv
in NaprotectrTribal interests. Beach/habitat-maintenance flow
and fish and wildlife, and to 4, a ch
ited 686
releases can bec
made 4-1
in years when no BHBF releases are made.
o. 1
N

Both beach/habitat-building and beach/habitat-maintenance flows, along with the
testing and evaluation of other types of releases under the AMP, were recommended by
the Service to verify a program of flows that would improve habitat conditions for
endangered fish. The proposed interim surplus criteria could affect the range of storage
conditions in Lake Powell and alter the flexibility to schedule and conduct such releases
or to test other flow patterns. The magnitude of this reduction in flexibility has been
evaluated in the FEIS for each interim surplus alternative.
S.1.6.2.3

Temperature Control at Glen Canyon Dam

In 1994, the Service issued a Biological Opinion on the Operation of Glen Canyon Dam
(BO). One of the elements of the reasonable and prudent alternative in the BO, also a
common element in the Glen Canyon Dam EIS, was the evaluation of methods to
control release temperatures and, if viable, implement controls. Reclamation agreed
with this recommendation and included it in the Operation of Glen Canyon Dam Final
Environmental Impact Statement and subsequent ROD.

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Reclamation has issued a draft planning report and EA entitled Glen Canyon Dam
Modifications to Controls and Downstream Temperatures (Reclamation, 1999). Based
on comments to this draft EA, Reclamation is currently in the process of preparing a
new draft EA on temperature control at Glen Canyon Dam.
Interim surplus criteria could result in new information related to temperature control at
Glen Canyon Dam. Data and information made available from analysis related to
interim surplus criteria will be utilized in the revised EA on temperature control at Glen
Canyon Dam. Such information would also be considered in the development of an
appropriate design for a temperature control device.
S.1.6.3

ACTIONS RELATED TO THE BIOLOGICAL AND CONFERENCE OPINION ON
LOWER COLORADO RIVER OPERATIONS AND MAINTENANCE

Reclamation prepared a BA in accordance with Section 7 of the ESA, addressing effects
of ongoing and projected routine lower Colorado River operations and maintenance
(Reclamation, 1996). After formal consultation, a Biological and Conference Opinion
(BCO) was prepared by the Service (Service, 1997). Pursuant to the reasonable and
prudent alternative and 17 specific provisions provided in the BCO, Reclamation is
taking various actions that benefit the riparian region of the lower Colorado River and
associated species. In particular, these actions include: 1) acquisition,ior
ter restoration and
protection of potential and occupied Southwestern willow flycatcher habitat;
he In 2017
of t
ept. ber 29,
2) extensive life history studies for Southwestern willow flycatcher along 400 miles of
v. D
m
the lower Colorado River and other areas; n 3) protection and enhancement of
atio andon Nove
N
o
endangered fish species throughjrisk assessments, assisted rearing and development of
ed
N va
inthea 4, archiv River. This five-year BCO provides ESA
protected habitats ed
along
lower Colorado
cit
686
compliance for Reclamation actions on the lower Colorado River until 2002.
14-1

No.

The BA and BCO contain life histories/status of lower Colorado River species,
descriptions of ongoing and projected routine operation and maintenance activities, the
Secretary’s discretionary management activities, operation and maintenance procedures,
endangered species conservation program, environmental baseline, effects of ongoing
operations, reasonable and prudent alternatives and supporting documentation useful in
this FEIS. The 1996 BA and the 1997 BCO did not anticipate or address the effects of
specific interim surplus criteria on the species considered. A separate Section 7 ESA
consultation is in progress for the proposed action.
S.1.6.4

LOWER COLORADO RIVER MULTI-SPECIES CONSERVATION PROGRAM

Following the designation of critical habitat for three endangered fish species on nearly
all of the lower Colorado River in April of 1994, the three Lower Basin states of
Arizona, California and Nevada, Reclamation and the Service initiated the Lower
Colorado River Multi-Species Conservation Program (LCRMSCP), which was one of
the reasonable and prudent provisions of the five-year BCO received in 1997. The
purpose of the LCRMSCP is to obtain long-term (50-year) ESA compliance for both
federal and non-federal water and power interests. The LCRMSCP is a partnership of

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federal, state, Tribal, and other public and private stakeholders with an interest in
managing the water and related resources of the lower Colorado River Basin. In August
1995, Interior and Arizona, California and Nevada entered into a Memorandum of
Agreement (MOA) and later a Memorandum of Clarification (MOC) for development
of the LCRMSCP. The purpose of the MOA/MOC was to initiate development of an
LCRMSCP that would accomplish the following objectives:
•

Conserve habitat and work toward the recovery of threatened and endangered
species and reduce the likelihood of additional species listing under the ESA;
and

•

Accommodate current water diversions and power production and optimize
opportunities for future water and power development.

The LCRMSCP is currently under development and it is anticipated that the final EISenvironmental impact report will be finalized in 2001. Once the LCRMSCP is accepted
by the Service, Reclamation and other federal agencies, as well as the participating nonfederal partners, will have achieved ESA compliance for ongoing and future actions.
Since the interim surplus criteria determination is scheduled to be completed prior to the
completion of the LCRMSCP, a separate Section 7 consultation is in progress with the
ior
Service on the anticipated effects of implementing the interim surplus criteria.
Inter 7
e

01
f th
pt. o er 29, 2
e
S.1.6.5
SECRETARIAL IMPLEMENTATION AGREEMENTb ELATED TO
R
v. D
i IVER W Novem
atRon onATER USE PLAN
CALIFORNIA’S COLORADO
jo N
Nava archived
in
Within California,ed allocation, of Colorado River water is stipulated by various
cit the 16864
existing agreements14among the seven parties with diversion rights. Recently, these
No.

parties have negotiated a Quantification Settlement Agreement that further defines the
priorities for use of Colorado River water in California. This agreement provides a
basis for various water conservation and transfer measures described in the CA Plan.
The water transfers would require changes in the points at which the Secretary would
deliver transferred water to various California entities, as compared with provisions in
existing water delivery contracts. The operational changes caused by the water
transfers are being addressed in separate NEPA and ESA documentation.
S.1.6.6

OFFSTREAM STORAGE OF COLORADO RIVER WATER AND DEVELOPMENT
AND RELEASE OF INTENTIONALLY CREATED UNUSED APPORTIONMENT IN
THE LOWER DIVISION STATES

The above titled rule establishes a procedural framework for the Secretary to follow in
considering, participating in, and administering Storage and Interstate Release
Agreements among the states of Arizona, California and Nevada (Lower Division
states). The Storage and Interstate Release Agreements would permit state-authorized
entities to store Colorado River water offstream, develop intentionally created unused
apportionment (ICUA) and make ICUA available to the Secretary for release for use in

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another Lower Division state. This rule provides a framework only and does not
authorize any specific activities. The rule does not affect any Colorado River water
entitlement holder’s right to use its full water entitlement, and does not deal with
intrastate storage and distribution of water. The rule only facilitates voluntary interstate
water transactions that can help satisfy regional water demands by increasing the
efficiency, flexibility and certainty in Colorado River management. A Finding of No
Significant Impact was approved on October 1, 1999.

S.2

ALTERNATIVES

S.2.1 DEVELOPMENT OF ALTERNATIVES
The FEIS considers five interim surplus criteria alternatives as well as a No Action
Alternative/baseline that was developed for comparison of potential effects. The five
action alternatives considered include the Basin States Alternative (preferred
alternative), the Flood Control Alternative, the Six States Alternative, the California
Alternative and the Shortage Protection Alternative. The following section discusses the
strategies and origins of the action alternatives. Other alternatives, including a proposal
by the Pacific Institute, were considered but eliminated from further analysis. Those
alternatives, and the reasons for their elimination from further analysis, are discussed in
ior
Chapter 2 of Volume I.
Inter

e
of th 29, 2017
pt. BASIN STATES ALTERNATIVES
S.2.1.1
ORIGINS OF CALIFORNIA, SIX STATESe
. D AND ber
ion v Novem
Nat Basin States its draft 4.4 Plan, a plan to
In 1997, California presentedvajthe other ed on
to o
n Na
rc iv
achieve a reduction d iits dependence h surplus water from the Colorado River,
ite in 6864, a on
c
through various conservation measures, water exchanges and conjunctive use programs.
-1
o. 14 the draft 4.4 Plan was the expectation that the Secretary would
N
One of the elements of
continue to determine surplus conditions on the Colorado River until 2015. California
proposed criteria on which the Secretary would base his determinations of surplus
conditions during the interim period.
In 1998, in response to California’s proposal of interim surplus criteria, the other six
states within the Colorado River Basin (Six States) submitted a proposal with surplus
criteria that were similar in structure to those in California’s proposal. Under the
proposal from the Six States, use of surplus water supplies would be limited depending
on the occurrence of various specified Lake Mead surface elevations. The interim
surplus criteria proposed by the Six States were used to formulate the “Six States
Alternative.”
California subsequently proposed specific interim surplus criteria that were attached to
the October 15, 1999 Key Terms for Quantification Settlement Among the State of
California, Imperial Irrigation District, Coachella Valley Water District, and
Metropolitan Water District of Southern California. California also updated, renamed
and re-released its 4.4 Plan in May 2000. The revised plan is now known as
California’s Colorado River Water Use Plan (CA Plan). The interim surplus criteria

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proposal stemming from the CA Plan and Quantification Settlement Agreement was
used to formulate the "California Alternative."
In July 2000, during the public comment period on the DEIS, Reclamation received a
draft proposal for interim surplus criteria from the seven Colorado River Basin States
(Seven States). After a preliminary review of that proposal, Reclamation published it in
the August 8, 2000 Federal Register for review and consideration by the public during
the public review period for the DEIS. Reclamation published minor corrections to the
proposal in a Federal Register notice of September 22, 2000. Reclamation derived the
Basin States Alternative in the FEIS from the draft Seven States Proposal.
S.2.1.2

UTILIZATION OF PROPOSALS FROM BASIN STATES

Various proposals submitted by individual Colorado River Basin states or groups of
states were used by Reclamation to formulate interim surplus criteria alternatives. In
recognition of the need to limit the delivery of surplus water at lower Lake Mead water
levels, these proposals specified allowable uses of surplus water at various triggering
levels.
The Secretary will continue to apportion surplus water consistent with the applicable
provisions of the Decree, under which surplus water is divided 50 percent to California,
rior
Inteintends to
e
46 percent to Arizona, and 4 percent to Nevada. The Secretary also 017
2
of th to MWD under surplus
appropriately report the accumulated volume of Dept.delivered 29,
water
. any forbearance arrangements made by
ber
em
conditions. The Secretary also intends tiohonor
to n v
Na watern Nov
various parties for the deliveryajosurplus ed o or reparations for future shortage
v of
in Na 4, archiv
conditions.
ted

ci
1686
. 14- OF ALTERNATIVES
S.2.2 DESCRIPTION
No
S.2.2.1

NO ACTION ALTERNATIVE AND BASELINE CONDITIONS

As required by NEPA, a No Action alternative must be considered during the
environmental review process. Under the No Action Alternative, determinations of
surplus would continue to be made on an annual basis, in the AOP, pursuant to the
LROC and the Decree as discussed above. The No Action Alternative represents the
future AOP process without interim surplus criteria. Surplus determinations consider
such factors as end-of-year system storage, potential runoff conditions, projected water
demands of the Basin States and the Secretary’s discretion in addressing year-to-year
issues. However, the year-to-year variation in the conditions considered by the
Secretary in making surplus water determinations makes projections of surplus water
availability highly uncertain.
The approach used in the FEIS for analyzing the hydrologic aspects of the interim
surplus criteria alternatives was to use a computer model that simulates specific
operating parameters and constraints. In order to follow CEQ guidelines calling for a
No Action alternative for use as a “baseline” against which to compare project

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alternatives, Reclamation selected a specific operating strategy for use as a baseline
condition, which could be described mathematically in the model.
The baseline is based on a 70R spill avoidance strategy (as described in Section
S.2.2.1.2). Reclamation has utilized a 70R strategy for both planning purposes and
studies of surplus determinations in past years. While the 70R strategy is used to
represent baseline conditions, it does not represent a decision by Reclamation to utilize
the 70R strategy for determination of future surplus conditions in the absence of interim
surplus criteria.
S.2.2.1.1

Approach to Surplus Water Determination

As discussed above, the 70R operating strategy is being used as a baseline to show
possible future operating conditions in the absence of interim surplus criteria. The
primary effect of simulating operation with the 70R operating strategy would be that
surplus conditions would only be determined when Lake Mead is nearly full.
S.2.2.1.2

70R Baseline Surplus Triggers

The 70R baseline strategy involves assuming a 70-percentile inflow into the system,
subtracting out the consumptive uses and system losses and checkingrior results to see
e the
if all of the water could be stored or if flood control releaseshe Int be required. If flood
would
017
ft
control releases would be required, additional waterpt.made available to the Lower
is o
29, 2
er
. De
Basin states beyond 7.5 maf. The notation 70R refersvembspecific inflow where 70
ion v No to the
Nat
percent of the historical natural runoff is less than this value (17.4 maf) for the Colorado
vajo hived on
a
River basin at Leeed in N
Ferry.
, arc

cit
864
4-16 approximately 1199 feet msl in 2002 to 1205 feet msl in
The 70R trigger o. 1rises from
N line

2050. The gradual rise of the 70R trigger line is the result of increasing water use in the
Upper Basin. Under baseline conditions, when a surplus condition is determined to
occur, surplus water would be made available to fill all water orders by holders of
surplus water contracts in the Lower Division states.
S.2.2.2

BASIN STATES ALTERNATIVE (PREFERRED ALTERNATIVE)

Reclamation has identified the Basin States Alternative as the preferred alternative in
the FEIS. The Basin States Alternative is similar to, and based upon, information
submitted to the Secretary by representatives of the governors of the states of Colorado,
Wyoming, Utah, New Mexico, Arizona, Nevada and California. After receipt of this
information (during the public comment period), Reclamation shared the submission
with the public (through the Federal Register and Reclamation’s surplus criteria web
sites) for consideration and comment. Reclamation then analyzed the states’
submission and crafted this additional alternative for inclusion in the FEIS. Some of the
information submitted for the Department’s review was outside of the scope of the
proposed action for adoption of interim surplus criteria and was therefore not included
as part of the Basin States Alternative (e.g., adoption of shortage criteria and adoption

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of surplus criteria beyond the 15-year period) as presented in this FEIS. With respect to
the information within the scope of the proposed action, Reclamation found the Basin
States Alternative to be a reasonable alternative and has fully analyzed all
environmental effects of this alternative in this FEIS. The identified environmental
effects of the Basin States Alternative are well within the range of anticipated effects of
the alternatives presented in the DEIS and do not affect the environment in a manner
not already considered in the DEIS.
Reclamation selected the Basin States Alternative as its preferred alternative based on
Reclamation’s determination that it best meets all aspects of the purpose and need for
the action, including the needs to remain in place for the entire period of the interim
criteria, to garner support among the Basin States that will enhance the Secretary’s
ability to manage the Colorado River reservoirs in a manner that balances all existing
needs for these precious water supplies, and to assist in the Secretary’s efforts to insure
that California water users reduce their over reliance on surplus Colorado River water.
Reclamation notes the important role of the Basin States in the statutory framework for
administration of Colorado River Basin entitlements and the significance that a sevenstate consensus represents on this issue. Thus, based on all available information, this
alternative appears to be the most reasonable and feasible alternative analyzed.

ior
Inter 17
0
f the
pt. o water9, 2 elevations to
The Basin States Alternative specifies ranges ofDe Mead er 2 surface
Lake
v.
mb
be used through 2015 for determiningatioavailability vesurplus water through 2016.
the n
No of
o
j N specific n
The elevation ranges are coupledo
Nava withhived uses of surplus water in such a way that,
in
rc to decline, the amount of surplus water would be
a
if Lake Mead’s surface elevation were
cited 16864,
reduced. The interim41 criteria would be reviewed at five-year intervals with the LROC
No.
(and additionally as needed), and revised as needed based upon actual operational
S.2.2.2.1

Approach to Surplus Water Determination

experience.
S.2.2.2.2

Basin States Alternative Surplus Triggers

The surplus determination elevations under the Basin States Alternative consist of the
tiered Lake Mead water surface elevations listed below, each of which is associated
with certain stipulations on the purposes for which surplus water could be used.
Proceeding from higher to lower water levels, the elevation tiers (also referred to as
levels) are as follows:
Tier 1 - 70R Line (approximately 1199 to 1201 feet msl)
Tier 2 - 1145 feet msl
Tier 3 - 1125 feet msl

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S.2.2.3

FLOOD CONTROL ALTERNATIVE

S.2.2.3.1

Approach to Surplus Water Determination

Under the Flood Control Alternative, a surplus condition is determined to exist when
flood control releases from Lake Mead are occurring or projected to occur in the
subsequent year. The method of determining need for flood control releases is based on
flood control regulations published by the Los Angeles District of the United States
Army Corps of Engineers (Corps) and the Field Working Agreement between the Corps
and Reclamation.
S.2.2.3.2

Flood Control Alternative Surplus Triggers

Under the flood control strategy, a surplus is determined when the Corps flood control
regulations require releases from Lake Mead in excess of downstream demand. If flood
control releases are required, surplus conditions are determined to be in effect. The
average flood control triggering elevation is approximately 1211 feet msl. In practice,
flood control releases are not based on the average trigger elevation, but would be
determined each month by following the Corps regulations. When a flood control
surplus is determined, surplus water would be made available for all established uses by
contractors for surplus water in the Lower Division states.
erior

Int
f the 9, 2017
S.2.2.4
SIX STATES ALTERNATIVE
pt. o
. De ember 2
v
tion n Nov
N Water Determination
S.2.2.4.1
Approach to Surplusa
vajo
ed o
in Na 4, archiv
d
The Six States cite
Alternative specifies ranges of Lake Mead water surface elevations to be
1686
used through 2015 for determining the availability of surplus water through 2016. The
. 14No
elevation ranges are coupled with specific uses of surplus water in such a way that, if
Lake Mead’s surface elevation were to decline, the amount of surplus water would be
reduced. The interim criteria would be reviewed at five-year intervals with the LROC
and as needed based upon actual operational experience.
S.2.2.4.2

Six States Alternative Surplus Triggers

The surplus determination elevations under the Six States Alternative consist of the
tiered Lake Mead water surface elevations listed below, each of which is associated
with certain stipulations on the purposes for which surplus water could be used. The
tiered elevations are as follows, proceeding from higher to lower water levels:
Tier 1 - 70R Line (approximately 1199 to 1201 feet msl)
Tier 2 - 1145 feet msl
Tier 3 - 1125 feet msl

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S.2.2.5

CALIFORNIA ALTERNATIVE

S.2.2.5.1

Approach to Surplus Water Determination

The California Alternative specifies Lake Mead water surface elevations to be used for
the interim period through 2015 for determining the availability of surplus water
through 2016. The elevation ranges are coupled with specific uses of surplus water in
such a way that, if Lake Mead’s surface elevation declines, the amount of surplus water
would be reduced.
S.2.2.5.2

California Alternative Surplus Triggers

The Lake Mead elevations at which surplus conditions would be determined under the
California Alternative are indicated by a series of tiered, sloping lines from the present
to 2016. Each tiered line would be coupled with limitations on the amount of surplus
water available at that tier. Each tier is defined as a trigger line that rises gradually year
by year to 2016, in recognition of the gradually increasing water demand of the Upper
Division states. The elevations associated with the three tiers are as follows:
Tier 1 - 1160 feet msl to 1166 feet msl
Tier 2 - 1116 feet msl to 1125 feet msl
Tier 3 - 1098 feet msl to 1102 feet msl

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
S.2.2.6
SHORTAGE PROTECTION ALTERNATIVE vemb
ation on No
ajo N
d
S.2.2.6.1
ApproachNav archive Determination
to Surplus Water
d in 64,
cite 168
14The Shortage Protection Alternative is based on maintaining an amount of water in
No. to provide a normal annual supply of 7.5 maf for the Lower
Lake Mead necessary
Division, 1.5 maf for Mexico and storage necessary to provide an 80 percent probability
of avoiding future shortages.
S.2.2.6.2

Shortage Protection Alternative Surplus Triggers

The surplus triggers under this alternative range from an approximate Lake Mead initial
elevation of 1126 feet msl to an elevation of 1155 feet msl at the end of the interim
period. At Lake Mead elevations above the surplus trigger, surplus conditions would be
determined to be in effect and surplus water would be available for use by the Lower
Division states. Below the trigger-elevation, surplus water would not be made
available.

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S.3
S.3.1

SUMMARY OF ENVIRONMENTAL CONSEQUENCES
USE OF MODELING TO IDENTIFY POTENTIAL FUTURE
COLORADO RIVER SYSTEM CONDITIONS

To determine the potential effects of the interim surplus criteria alternatives, modeling
of the Colorado River system was conducted. Modeling provides projections of
potential future Colorado River system conditions (i.e., reservoir surface elevations,
river flows, salinity, etc.). The modeling results allow a comparison of potential future
conditions under the various interim surplus criteria alternatives and baseline
conditions. As such, much of the analyses contained within the FEIS are based upon
potential effects of changed flows and water levels within the Colorado River and
mainstream reservoirs.
S.3.2 BASELINE CONDITIONS
As discussed above, the No Action Alternative does not provide consistent specific
criteria for determining surplus conditions. As such, it is not possible to model the No
Action Alternative. However, in order to provide a reasonable analytical projection of
potential future system conditions without interim surplus criteria, a reasonable baseline
surplus strategy (70R) was utilized. This baseline represents a definablersurplus criteria
terio
he In 2017 secretarial
based on recent operational decisions. The 70R strategy is tbased upon recent
. of of 29,
operating decisions and was modeled to develop aept
projectioner baseline conditions for
v. D vemb
comparison with the alternatives in NatFEIS.
the ion
No

on
jo
Nava archived
S.3.3 IMPACTted in
DETERMINATION APPROACH
4,
ci
1686
14The analysis of potential effects for each issue considered is based primarily upon the
No.

results of modeling. Following the identification of conditions important to each issue,
the potential effects of various system conditions over the general range of their
possible occurrence (as identified by the range of modeling output for various
parameters) are identified for each issue. The potential effects of the various interim
surplus criteria alternatives are presented in terms of the incremental differences in
probabilities (or projected circumstances associated with a given probability) between
baseline conditions and the alternatives.
S.3.4 PERIOD OF ANALYSIS
The FEIS addresses interim surplus criteria that would be used during the years 2001
through 2015 for determining whether surplus water would be available during the
years 2002 through 2016. Due to the potential for effects beyond the 15-year interim
period, the modeling and impact analyses extend through the year 2050. It is important
to note that modeling output and associated impact analyses become more uncertain
over time as a result of increased uncertainty of future system conditions (including
hydrologic conditions), as well as uncertainty with regard to future operational
decisions that will affect circumstances within the Colorado River system.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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EXECUTIVE SUMMARY

S.3.5 POTENTIALLY AFFECTED AREA
Interim surplus criteria could affect the operation of the Colorado River system (i.e.,
reservoir levels and river flow volumes) as a result of surplus determinations and
associated water deliveries that may not have occurred in the absence of such criteria.
Interim surplus criteria are based on system conditions and hydrology. Water supply to
the Lower Division states of Arizona, California and Nevada is achieved primarily
through releases and pumping from Lake Mead. As a result of Lake Powell and Lake
Mead equalization requirements, interim surplus criteria effects on Lake Mead surface
elevations could also influence Lake Powell surface elevations and Glen Canyon Dam
releases. However, operation of the other Upper Basin reservoirs is independent of
Lake Powell. Therefore, the upstream limit of the potentially affected area under
consideration in this FEIS is the full pool elevation of Lake Powell. The downstream
limit within the United States is the Southerly International Boundary (SIB) between the
United States and Mexico (see Map S-1). Also addressed in the FEIS are potential
transboundary impacts in Mexico pursuant to Executive Order 12114 - Environmental
Effects Abroad of Major Federal Actions, January 4, 1997, and the July 1, 1997 Council
on Environmental Quality (CEQ) Guidelines on NEPA Analyses for Transboundary
Impacts.

ior
Inter it is recognized
In addition to influencing conditions within the Colorado fRiver system, 17
the
0
pt. ofrom r 29, 2surplus criteria
that continued delivery of surplus water that coulde
result beinterim
v. D
would recognize ongoing and proposedtistate actionsovemLower Basin. These actions
a on on N in the
N
could result in environmentalvajo outside of the river corridor. However, these
Na effectschived
in
actions have independent utility , ar are not caused by or dependent on interim surplus
cited 16864 and
criteria for their implementation. Environmental compliance would be required on a
14No.
case-by-case basis prior to their implementation. Therefore, Reclamation determined
that the appropriate scope of this analysis is to consider only those potential effects that
could occur within the Colorado River corridor as defined by the 100-year flood plain
and reservoir maximum water surface elevations.
S.3.6 COMPARISON OF SURPLUS ALTERNATIVES TO BASELINE
CONDITIONS
S.3.6.1

EFFECTS ON RESERVOIR SURFACE ELEVATIONS AND RIVER FLOWS

Figures S-1 and S- 2 present the 90th, 50th and 10th percentile Lake Powell and Lake
Mead surface elevations indicated through system modeling for baseline conditions and
the interim surplus criteria alternatives. These figures can be used for comparing the
relative differences in the general lake level trends that result from the simulation of
future conditions under the baseline and the interim surplus criteria alternatives. A
complete explanation of the modeling process and results can be found in Section 3.3 of
the FEIS.

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Figure S-1
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values
3720
90th Percentile

3700
3680

Water Surface Elevation (feet)

3660
50th Percentile

3640
3620
3600
10th Percentile

3580
Baseline Conditions

3560

Basin States Alternative
Flood Control Alternative

3540
Six States Alternative

3520

California Alternative
Shortage Protection Alternative

3500
2000

r
2040 io
Inter 12045
0 7
f the
pt. o er 29, 2
Figure S-2 e
b
v. D v Elevations
Lake Mead End-of-December Water em
ation on and Baseline Conditions
No
Comparison of ajo N Alternatives
Surplus
v th th and 10thd
e
in Na904,,50 rchiv Percentile Values
a
d
cite 1686
14No.
2005

2010

2015

2020

2025

2030

2035

2050

Year

1220

1200

90th Percentile

1180

1160
Wa
ter
Su 1140
rfa
ce
Ele
1120
vat
ion
(fe
et) 1100

50th Percentile

1080

1060

1040

Baseline Conditions
Basin States Alternative
Flood Control Alternative

1020

Six States Alternative
California Alternative

10th Percentile

Shortage Protection Alternative

1000
2000

2005

2010

2015

2020

2025
Year

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
22

2030

2035

2040

2045

2050

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EXECUTIVE SUMMARY

As illustrated in Figure S-1, the Flood Control Alternative could potentially result in the
highest Lake Powell water levels. The Shortage Protection Alternative and the
California Alternative could potentially result in the lowest water levels. The baseline
conditions yield similar levels to those observed under the Flood Control Alternative.
The water levels observed under the California Alternative are similar to those observed
under the Shortage Protection Alternative. The results obtained under the Six States
and Basin States alternatives are similar, and fall between baseline conditions and the
Shortage Protection Alternative.
As illustrated in Figure S-2, the Flood Control Alternative could potentially result in the
highest Lake Mead water levels. The California Alternative could potentially result in
the lowest water levels. The water levels observed under the Shortage Protection
Alternative are similar to those of the California Alternative, with some years slightly
lower. The baseline conditions yield slightly lower levels than the Flood Control
Alternative, but the differences are very small. The results obtained under the Six States
and Basin States alternatives are similar, and fall between the Flood Control and
Shortage Protection alternatives.
River flows would be affected to a limited degree by the interim surplus criteria
ior
alternatives. Flows from Glen Canyon Dam, which would be influenced by the
Inter 17
adoption of interim surplus criteria, will remain within the range of , 20 analyzed in
f the 9flows
pt. o potential changes in the
detail in the Glen Canyon Dam EIS. Therefore,De
effects of ber 2
m
n v.
frequencies of these flows on downstream resourcesove no further analysis outside of
Natio d on N need
o
the ROD for Glen Canyon Dam joperations and the Adaptive Management Program.
Nava
hive

in
arc
cited 16864,
River flows in the reaches between Hoover Dam and the SIB would also be affected to
. 14N by
a limited degree o the interim surplus criteria alternatives. Flows to meet downstream

demands would typically increase, but remain well within the current operational ranges
for those reaches. The frequency of large flows in those reaches due to flood control
releases at Hoover Dam would typically decrease. Detailed discussions of the potential
effects on river flows are included in Sections 3.3 and 3.6 of the FEIS.
S.3.6.2

SUMMARY OF ENVIRONMENTAL IMPACTS

Table S-1 summarizes the potential effects of interim surplus criteria on the various
resource issues analyzed in the FEIS.
S.3.6.3

ENVIRONMENTAL COMMITMENTS

Impacts are associated with changes in the difference between probabilities of
occurrence for specific resource issues under study when comparing the action
alternatives to baseline conditions. Reclamation has determined that most of the
potential impacts identified are not of a magnitude that would require specific
mitigation measures to reduce or eliminate their occurrence because the small changes
in probabilities of occurrence are within Reclamation’s current operational regime and

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authorities under applicable federal law. In recognition of potential effects that could
occur under baseline conditions or with implementation of the interim surplus criteria
alternatives under consideration, Reclamation has developed a number of environmental
commitments, described below, that will be undertaken if interim surplus criteria are
implemented. Some commitments are the result of compliance with specific
consultation requirements.
S.3.6.3.1

Water Quality

Reclamation will continue to monitor salinity and total dissolved solids on the Colorado
River as part of the ongoing Colorado River Basin Salinity Control Program to ensure
compliance with the numeric criteria on the river as set forth in the Forum’s 1999
Annual Review.
Reclamation will continue to participate in the Lake Mead Water Quality Forum and the
Las Vegas Wash Coordination Committee as a principal and funding partner in studies
of water quality in the Las Vegas Wash and Lake Mead. Reclamation is an active
partner in the restoration of the Las Vegas Wash wetlands.
Reclamation is acquiring and will continue to acquire riparian and wetland habitat
around Lake Mead and on the Lower Colorado River related to ongoing rand projected
terio
routine operations.
he In
017
ft

o
9, 2
ept.
. DNevadamber 2 of Environmental
Reclamation will continue to participateion vthe ove Division
t with n N
NaCompany in the perchlorate remediation program
o
Protection and Kerr-McGee Chemical ed o
avaj rc iv
of groundwater dischargeN
in points,alonghLas Vegas Wash that will reduce the amount of
4 a
c ted 1 the Colorado River.
this contaminantientering 686
14No.
Reclamation will continue to monitor river operations, reservoir levels and water supply
and make this information available to the Colorado River Management Work Group,
agencies and the public. See also Reclamation’s website (http://www.lc.usbr.gov and
http://www.uc.usbr.gov).
S.3.6.3.2

Riverflow Issues

Reclamation will continue to work with the stakeholders in the Adaptive Management
Program to develop an experimental flow program for the operations of Glen Canyon
Dam which includes BHBFs and is designed to protect, mitigate adverse impacts to and
improve the values for which GCNP and GCNRA were established.
S.3.6.3.3

Aquatic Resources

Reclamation will initiate a temperature monitoring program below Hoover Dam with
state and other federal agencies to document temperature changes related to baseline
and implementation of interim surplus criteria and assess their potential effects on listed

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EXECUTIVE SUMMARY

species and the sport fishery. The existing hydrolab below Hoover Dam will be
modified as necessary to provide this temperature data.
S.3.6.3.4

Special-Status Species

Section 7 consultation is in progress and commitments will be identified in the Record
of Decision.
S.3.6.3.5

Recreation

Reclamation is initiating a bathymetric survey of Lake Mead in fiscal year 2001 and
will coordinate with the Lake Mead National Recreation Area to identify critical
recreation facility elevations and navigational hazards that would be present under
various reservoir surface elevations.
Reclamation will continue to monitor river operations, reservoir levels and water supply
and make this information available to the Colorado River Management Work Group,
agencies and the public. This operational information will provide the Lake Mead
National Recreation Area and the Glen Canyon National Recreation Area with
probabilities for future reservoir elevations to assist in management of navigational aids,
recreation facilities, other resources and fiscal planning.
rior

Inte 1
f the the Glen 7
o
Reclamation will continue its consultation and coordination with29, 20 Canyon
ept.
. Don theember
National Recreation Area and the Navajo Nation
development of Antelope Point
nv
Natio d on Nov
as a resort destination.
vajo
e
in Na 4, archiv
d Resources
cite
S.3.6.3.6
Cultural1686
14No.continue to consult and coordinate with the State Historic
Reclamation shall
Preservation Officer, the Advisory Council on Historic Preservation (Council), Glen
Canyon National Recreation Area, Lake Mead National Recreation Area, Tribes and
interested parties with regard to the potential effects of the proposed action as required
by Sections 106 and 110 of the National Historic Preservation Act following the
Council’s recommended approach for consultation for the Protection of Historic
Properties found at 36 CFR 800.
S.3.6.3.7

Transboundary Impacts

It is the position of the United States State Department, through the United States
Section of the International Boundary and Water Commission (USIBWC), that the
United States does not mitigate for impacts in a foreign county. The United States will
continue to participate with Mexico through the USIBWC Technical Work Groups to
develop cooperative projects beneficial to both countries.

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S.4

OTHER NEPA CONSIDERATIONS

S.4.1 CUMULATIVE IMPACTS
A cumulative impact is an impact that results from the incremental impact of the action
when added to other past, present and reasonably foreseeable future actions regardless
of what agency (federal or non-federal) or person undertakes such other actions.
Cumulative impacts can result from individually minor but collectively significant
actions taking place over a period of time (40 CFR 1508.7).
Effects that could occur within the United States as a result of interim surplus criteria
are each associated with potential changes in the probabilities for Lake Mead and Lake
Powell surface elevation reductions and changes in Colorado River flows from Glen
Canyon Dam to the SIB. Generally, other actions that could result in cumulative
impacts when considered in tandem with the effects of interim surplus criteria have
been incorporated into modeling of future system conditions. Such actions include
future increases in consumptive use of Colorado River water in the Upper Division
states, intrastate water transfers in the Lower Division states and various requirements
and constraints applied to the operation of the Colorado River system.

or
The environmental effects of the various components of the CA Plan, iincluding the
Inter 17
various intrastate storage facilities (such as Cadiz, Hayfield/Chuckwalla and
0
f the
pt. o er 29, 2 undergoing
Desert/Coachella projects) and the other relatedDe ongoing actions, are
and
b
v.
separate compliance. Where there is ation nexus toem
a federal
Nov actions in California, a
on
jo N
combined California Environmental Quality Act (CEQA) and NEPA compliance
Nava archived
document is beinged in
cit prepared. 64,

8
4-16
. 1effects to the resources affected by surplus criteria were analyzed
No
Potential cumulative
within the 100-year floodplain of the lower Colorado River from the full-pool elevation
of Lake Powell to the Gulf of California in Mexico through year 2050. Only the issue
area of “transboundary impacts” was identified as possibly experiencing cumulative
effects.
No past, present or reasonably foreseeable actions in the United States are expected to
result in cumulative impacts to the issue area of transboundary impacts. In addition to
the direct and indirect effects on the physical and natural environment in Mexico from
actions identified by Mexico, it is recognized that some future actions taken by Mexico
may have a cumulative effect. Exactly what these action are is not known at this time.
Any impacts of these projects are the responsibility of Mexico.
In addition, Reclamation is consulting with the Service on potential adverse effects to
species found in both Mexico and the United States. For potentially affected species
found only in Mexico, Reclamation is consulting with the National Marine Fisheries
Service. Concurrent with these consultations, Reclamation is also continuing dialog
with Mexico, through the IBWC’s Fourth Technical Work Group, to reach mutually
agreeable solutions to address cumulative impacts.

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S.4.2 RELATIONSHIP BETWEEN SHORT-TERM USES OF THE
ENVIRONMENT AND LONG-TERM PRODUCTIVITY
Because the implementation of interim surplus criteria is a management action that
would require no direct physical change to the environment, for the purposes of this
discussion, short-term uses of resources are limited to potential changes in the
probability for certain environmental effects to occur as a result of changed system
conditions. Also for the purposes of this discussion, long-term productivity refers to the
benefits that would be realized during and following the period in which interim surplus
criteria would be in place.
The benefit sought by means of the interim surplus criteria alternatives consists of
increasing the efficiency of the Secretary's annual decision-making process regarding
the availability of Colorado River water. This would afford the mainstream users of
this water a greater degree of predictability which would assist them in their water
resources planning and operation.
The resources that may be affected in the short-term would be primarily those affected
by lower reservoir levels. The effects of the interim surplus criteria on those resources
would depend on the alternative selected for implementation. The Flood Control
Alternative would result in insignificant changes in reservoir levelserior baseline
nt from
conditions. The other four alternatives would tend to causethe I average 7
lower 201 water levels
of
,
than baseline conditions by 2016 and for a limitedept. ofber 29
period time thereafter. However,
.D
nv
em
these alternatives would have a greater tprobabilityNosurplus water than the Flood
Na io d on of v
o
Control Alternative or baseline conditionse
avaj r hiv through the year 2016. Long-term benefits
in Nto interimcsurplus criteria would include increased
that would be realized due 64, a
cited 168
opportunities for making more efficient use of Colorado River water supplies.
14-

No.

S.4.3 IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF
RESOURCES
Irreversible commitments are decisions affecting renewable resources such as soils,
wetlands and waterfowl habitat. Such decisions are considered irreversible because
their implementation would affect a resource that has deteriorated to the point that
renewal can occur only over a long period of time or at great expense or because they
would cause the resource to be destroyed or removed.
The application of the interim surplus criteria would include reviews at five-year
intervals to consider the workability of the criteria in light of the multiple purposes
served by the operation of the Colorado River system, including environmental
maintenance. Based on those reviews, interim surplus criteria could be revised or
eliminated as needed. If California fails to meet its water conservation and management
goals throughout the stipulated term of implementation of the criteria (through 2016),
the Secretary may choose to terminate the interim criteria and revert to the 70R strategy.
Finally, after 2016, determinations of the availability of surplus will revert to the AOP
process.

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None of the resources assessed in the FEIS would experience a deterioration in
condition such that the resource would be destroyed or removed as a result of
implementation of interim surplus criteria or under the No Action Alternative. The
Colorado River System may also reset at any time in the future, due to high inflows
resulting in full reservoirs. There would be no construction of facilities needed to
facilitate the Secretary's determination of surplus water under the criteria.
Irretrievable commitment of natural resources means loss of production or use of
resources as a result of a decision. It represents opportunities foregone for the period of
time that a resource cannot be used.
All of the resources assessed in the FEIS would continue to be available for production
or use under any of the alternatives; however, application of the interim surplus criteria
may result in a determination for any given year that surplus water is available from the
Colorado River. That water could also have been determined to be surplus in the
absence of interim surplus criteria through the AOP process. Although water is a
renewable resource, the delivery of surplus water under all of the alternatives, including
no action, would irretrievably commit (to beneficial consumptive uses) the water
declared to be surplus, but authorized by the Law of the River.

S.5

CONSULTATION AND COORDINATION Interior
17
the

. of
m
Nove

, 20

9
S.5.1 GENERAL PUBLIC INVOLVEMENT ept
. D ACTIVITIES
ber 2

nv
Natiotod on consisted essentially of two
j leading e the FEIS
The public involvement programo
Nava a hearings
in and public rchiv and public review of the DEIS.
phases: project scoping,
cited 16864,
14S.5.1.1
PROJECT SCOPING
No.
In 1999, Reclamation conducted a public scoping process that featured public scoping
meetings to inform interested parties of the purpose and need for the development of
interim surplus criteria, and to obtain public comment to assist in identifying the scope
of the proposed action and environmental issues to be addressed in the DEIS. The
scoping meetings were held in June 1999 at Las Vegas, Nevada; Phoenix, Arizona;
Ontario, California; and Salt Lake City, Utah. The meetings were announced in Federal
Register notices on May 18, 1999 and May 28, 1999, on Reclamation’s Lower Colorado
Region internet website, and by a press release on May 28, 1999. The press release was
mailed not only to the media but also to hundreds of federal, state and local agencies,
non-governmental organizations and private citizens known to have an interest in
Colorado River operations. The public was asked to identify any concerns about
development and implementation of the interim surplus criteria.
Public comments in the form of letters to Reclamation (35 letters) and oral responses at
the scoping meetings (eight presenters) expressed numerous concerns regarding the
effect of the proposed interim surplus criteria on the future quantity of water available
from the Colorado River, and other resource issues. Based on the scoping comments,

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Reclamation issued a Notice of Intent to prepare the DEIS in the Federal Register on
December 7, 1999.
Reclamation also discussed the development of the proposed interim surplus criteria
with various agencies and groups at their own regular meetings or at meetings set up by
Reclamation. Included were Indian Tribes and Indian Communities having allocations
of Colorado River water, Basin States water resource departments, various water
agencies within the States, contractors for federal hydropower, environmental groups
water agencies of the United Mexican States (Mexico). The coordination activities with
each agency or group are summarized below. Table S-2 lists the agencies and
organizations that were invited to such meetings by letter, and/or met with Reclamation
regarding interim surplus criteria on other occasions.
S.5.1.2

PUBLIC REVIEW OF DEIS

The DEIS was distributed to interested Federal, Tribal, State and Local entities and
members of the general public for a 60-day review when it was filed with EPA on July
7, 2000, and announced in the Federal Register. The DEIS was sent to 407 interested
parties on Reclamation’s mailing list, and a copy of the DEIS was made available for
public viewing on Reclamation’s Lower Colorado Region web site. Reclamation
conducted a public technical meeting at Las Vegas, Nevada on Augustor 2000, to
nteri 15,
provide information and answer questions regarding theof the I process 7 analysis
modeling 201 for
9,
pt.
in the DEIS. Between August 21 and August 24, 2000, Reclamation conducted public
. De ember 2
nv
hearings on the DEIS in Ontario, California; Las Vegas, Nevada; Salt Lake City, Utah;
Natio d on Nov
o
and Phoenix, Arizona.
avaj
ive

in N
rch
ited 6864, a
c review1
When the public
- period closed on September 8, 2000, Reclamation received 68
o. 14 public which, along with Reclamation's responses, are
comment letters from the
N

included in Volume III of the FEIS. Individual comments from the public resulted in
technical and editorial changes to the document. These included a change in the
baseline operating strategy, better definition of Tribal water rights and diversions,
inclusion of the Basin States Alternative and refinements in descriptions of alternatives
and operational modeling results.
After the DEIS was completed and ready for public review and comment, Reclamation
received the document “Interim Surplus Guidelines, Working Draft” from the Seven
Basin States (Seven States Proposal). Reclamation made a preliminary review of the
specific surplus criteria in the information presented by the basin states, and made a
preliminary determination that the criteria were within the range of alternatives and
impacts analyzed in the DEIS. After its review of the Seven States Proposal,
Reclamation published it in the Federal Register of August 8, 2000, for review and
consideration by the public during the public review period for the DEIS.

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S.5.2 FEDERAL AGENCY COORDINATION
S.5.2.1

NATIONAL PARK SERVICE

NPS is a cooperating agency with Reclamation for the purpose of NEPA compliance for
the interim surplus criteria, in recognition of its administration of national park and
recreation areas along the Colorado River corridor. NPS staff participated in numerous
meetings with Reclamation’s project evaluation team and participated in internal
document reviews as sections of the DEIS were being prepared. This facilitated close
coordination with the NPS regarding resources and facilities potentially effected and the
nature of the effects. The NPS offices involved in these activities are those at the
GCNRA, Grand Canyon National Park and the LMNRA, under the coordination of the
office at the GCNRA.
S.5.2.2

U.S. SECTION OF THE INTERNATIONAL BOUNDARY AND WATER
COMMISSION

The United States Section of the IBWC (USIBWC) is a cooperating agency with
Reclamation for the purposes of NEPA compliance for the interim surplus criteria, in
recognition of its administration of Treaty obligations with Mexico. As such, USIBWC
staff participated in numerous meetings with Reclamation’s projecterior
t evaluation team and
Inwere being prepared.
participated in internal document reviews as sections of thethe
017
f DEIS
p . o er 29 2
This facilitated close coordination with the USIBWCtin developing ,information needed
. De
b
for this FEIS and in Reclamation’s participation in the consultation with Mexico. The
ion v Novem
at
USIBWC head office at El avajo N was directly involved.
Paso, Texas ved on
S.5.2.3

in N 4, archi
ited OF INDIAN AFFAIRS
c
U.S. BUREAU 686
-1
o. 14
N

The Bureau of Indian Affairs (BIA) administers programs to promote Tribal economic
opportunity, and to protect and improve Indian Trust Assets. The BIA assisted
Reclamation with the Tribal consultation, and generally served in an advisory capacity
to the Tribes. Through letters of comment on the DEIS, the BIA further amplified
Tribal concerns regarding Colorado River operations and the interim surplus criteria.
S.5.2.4

U.S. FISH AND WILDLIFE SERVICE INCLUDING ENDANGERED SPECIES ACT
COMPLIANCE

Under Section 7(a)(2) of the Endangered Species Act (ESA), 16 U.S.C. δ 1536 (a)(2),
each Federal agency must, in consultation with the Secretary (either the Secretary of
Commerce through the National Marine Fisheries Service or the Secretary of the
Interior through the Fish and Wildlife Service), insure that any discretionary action
authorized, funded, or carried out by the agency is not likely to jeopardize the continued
existence of any listed species or result in the destruction or adverse modification of
designated critical habitat. To assist agencies in complying with the requirements of
Section 7(a)(2), ESA’s implementing regulations set out a detailed consultation process

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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for determining the biological impacts of a proposed discretionary activity. The
consultation process is described in regulations promulgated at 50 C.F.R. δ 402.
Adoption of specific interim surplus criteria by the Secretary is a discretionary federal
action and is therefore subject to compliance with the ESA. On May 22, 2000,
Reclamation provided the Service a memorandum identifying listed or proposed species
and designated critical habitat that may be present in the action area. The Service
provided a response to Reclamation on June 5, 2000, which concurred with
Reclamation’s list and added two species: Bald Eagle and Desert Pupfish. This
information was used to assess potential effects of the proposed interim surplus criteria.
Reclamation prepared a biological assessment (BA) which addresses the effects of both
interim surplus criteria and the California water transfers, to reduce the consultation
time frame on these two independent operational actions on the lower Colorado River.
The BA and memorandum requesting formal consultation were mailed to the Service on
August 31, 2000.
The action area for the BA identified above is the 100-year floodplain of the Colorado
River to the SIB and the full pool elevations of Lakes Mead, Mohave and Havasu.
Implementation of the interim surplus criteria is not expected to effect any listed species
upriver of Lake Mead (full pool elevation) nor impact implementationior any provisions
ter of
he In the2United States,
of the existing BO on the operation of Glen Canyon Dam. t
017
f Within
pt. o to r 29, any listed species
implementation of interim surplus criteria is notDe
v. anticipatedbe effect
o the N Colorado
in areas beyond the 100-year floodplain iofn lowerovem River and the full pool
Nat d on
elevations of lakes Mead,Navajo and Havasu. Consultation with the Service is in
Mohave
hive
d in 6consultation will be identified in the ROD.
progress and the iresults of the 4, arc
c te

168
. 14- of the effects of adopting interim surplus criteria on listed
No
Preliminary evaluations

species which may be present in the river corridor below Glen Canyon Dam led to the
conclusion that there would be no affect. More recent output, resulting from refinement
of the model used to predict future dam operations and riverflows, indicated that there
would be a minor change in the frequency with which flows recommended by the 1995
biological opinion would be triggered, but that such changes would not adversely affect
any listed species between Glen Canyon Dam and Lake Mead. Reclamation is
consulting with the Service on these changes.
Reclamation is also consulting with the Service regarding special status species in
Mexico. To facilitate consultation, Reclamation prepared a supplemental biological
assessment (BA) addressing the potential effects of interim surplus criteria along the
Colorado River corridor in Mexico from the SIB to the Sea of Cortez. Consultation is
in progress and the results of the consultation will be identified in the ROD.
S.5.2.5

NATIONAL MARINE FISHERIES SERVICE

The National Marine Fisheries Service (NMFS) administers programs that support the
domestic and international conservation and management of living marine resources.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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EXECUTIVE SUMMARY

Under Section 7(a)(2) of the ESA, NMFS is the responsible Federal agency for
consultation on special-status marine species. Reclamation consulted with NMFS
regarding the special-status fish at the upper end of the Sea of Cortez. The consultation
was facilitated by a BA supplementing the BA described in Section S.5.2.4 on the
Colorado River corridor in Mexico. Consultation is in progress and the results of the
consultation will be identified in the ROD.
S.5.2.6

NATIONAL HISTORIC PRESERVATION ACT COMPLIANCE

Section 106 of the National Historic Preservation Act (NHPA) of 1966, as amended,
requires all Federal agencies to take into account the effects of their actions on
historic properties, and to afford the Advisory Council on Historic Preservation
(Council) a reasonable opportunity to comment when an action will have an effect
on historic properties. The Council’s recommended approach for consultation for
the Protection of Historic Properties is found at 36 CFR 800 (FR Vol. 64, No. 95,
May 18, 1999, pages 27071-27084).
The first step of the Section 106 process, as set forth at 36 CFR 800.3(a), is for the
Agency Official to determine whether the proposed Federal action is an undertaking
as defined in §800.16(y) and, if so, whether it is a type of activity that has the
potential to cause effects to historic properties. Reclamation has determined
erior
Intthe definition of
development and implementation of interim surplus criteria he
f t meets9 2017
pt. o to effect, historic
an undertaking, but an undertaking that is withoute
. D potentialber 2
n vthe rationale for its decision are
em
properties. Reclamation’s determinationo
Nati and on Nov
documented in Section 3.13 ofajo FEIS.ved 36 CFR 800.3(a)(1), if the undertaking
Nav the hi Per
does not have theted in to64, areffects on historic properties, the Agency
potential cause c
ci
168
Official has no further obligations under Section 106 or this part, Reclamation has
. 14- to take into account the effects of the development and
No
fulfilled its responsibilities
implementation of interim surplus criteria on historic properties.
The Nevada State Historic Preservation Officer (SHPO) submitted written
comments on the cultural resources section of the DEIS. The SHPO has indicated
they do not agree with Reclamation’s position in the DEIS that development and
implementation of interim surplus criteria is an undertaking without potential to
affect historic properties, and so complying with the consultation requirements of
the NHPA is not necessary.
The Nevada SHPO has stated that their opportunity to comment on effects to
historic properties has been precluded by Reclamation and the Department’s
finding, and have asked that the matter be referred to the Council. Under the
implementing regulations for Section 106, when there is a disagreement between an
agency and a SHPO concerning the effect of an undertaking, the matter must be
referred to the Council for comment and resolution. Reclamation believes the
Council will agree with the Nevada SHPO that Section 106 compliance is necessary
for this proposed action. Reclamation’s position is that this is not an action
requiring Section 106 compliance, but more appropriately falls under Section 110 of

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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EXECUTIVE SUMMARY

the NHPA. Reclamation has prepared a memorandum discussing this issue and has
forwarded it to the Council for review and further consultation.
S.5.3 TRIBAL CONSULTATION
Reclamation has been coordinating river operations with the Indian Tribes and
communities who have entitlements to or contracts for Colorado River water, and
those that may be affected by the proposed action. Representatives of various
Tribes attended the scoping meetings in May 1999, and some provided Reclamation
with written comments on the proposal for interim surplus criteria. Beginning in
May 1999, Reclamation has had numerous meetings with the various Tribes who
have an interest in the implementation of the interim surplus criteria. The Tribes
and communities fall generally into four groups: 1) the Colorado River Basin Indian
Tribes (Ten Tribes Partnership) who have diversion rights from the Colorado River
main stream and various tributaries; 2) the Tribes and Communities of central
Arizona; 3) the Tribes in the Coachella Valley Consortium of Mission Indians; and
4) other Tribes or Indian Communities who do not have a Colorado River water
entitlement but nevertheless have an interest in the availability and distribution of
Colorado River water. The individual Tribes and Indian Communities in each of
these groups are listed on Table S-2 at the end of this chapter.

ior
Inter rights be
A primary concern of the Ten Tribes Partnership was thatf Tribal water 017
the
t. each Tribe 2
pforo er 29,be included in
clearly acknowledged and that the diversion point(s)
. De
b
ion v No tribal
the operational model so as to more accurately reflect vem diversions in the
at
on
jo N
modeling. Other concerns included overreliance on unused Tribal water allocations
Nava archived
in
by non-Tribal diverters, and Lake Powell water level fluctuations with respect to
cited 16864,
resort development 14opportunity. Reclamation provided financial assistance to the
No.
Ten Tribes Partnership to assist the Tribes in cataloging their Colorado River
depletion rights and conducting an active coordination process with Reclamation in
connection with the interim surplus criteria. Using information provided by the
Tribes, Reclamation added the diversion points to the model for the FEIS.
S.5.4 STATE AND LOCAL WATER AND POWER AGENCIES
COORDINATION

Since the May 18, 1999 Federal Register notice announcing the development of interim
surplus criteria, Reclamation has had various discussions with state and local water and
power agencies regarding the proposed interim surplus criteria. However, the
development of surplus criteria has been the subject of discussions for many years prior
to 1999. Reclamation meets regularly with representatives of the Basin States, Indian
Tribes and communities, environmental organizations, and other stakeholders as part of
the Colorado River Management Work Group. Reclamation coordinates the
development of the Annual Operating Plan (AOP) for the Colorado River system
through this group as required by federal law. It was through such coordination actions
that Reclamation originally presented the alternative surplus strategies.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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EXECUTIVE SUMMARY

The Basin States provided Reclamation with projections of the future depletions of the
Colorado River water anticipated by water agencies in each state. The Upper Colorado
River Commission compiled Upper Basin depletions, and the Lower Division states
compiled their respective depletions. The projections were used as input to
Reclamation’s operational modeling analysis.
Reclamation also conducted coordination with water agencies in southern California
regarding the environmental documentation being prepared for various components of
California’s Colorado River Water Use Plan.
In the early summer of 2000, the seven Basin States acting as a group, independently
from Reclamation, formulated the Seven States Proposal for interim surplus criteria
which they provided to Reclamation after the DEIS was prepared. Letters of comment
on the DEIS from some of the Basin States contained additional commentary on the
draft proposal.
S.5.5 NON-GOVERNMENTAL ORGANIZATIONS COORDINATION
Several environmental organizations have expressed interest in the project and have
attended one or more public and independent meetings with Reclamation. The Pacific
Institute for Studies in Development, Environment and Security (PacificrInstitute),
terio
representing a consortium of environmental organizations, the In an interim surplus
submitted 017
2
of
criteria proposal to Reclamation in February 2000. pt. proposal included an additional
e The ber 29,
.D
em
allocation of water to Mexico for environmental purposes. The Pacific Institute’s
ion v
Natrole d on Novother environmental groups
interest in the project and coordinating ve among the
vajo
in Na 4, archi
contributed to theted
i coordination with Reclamation by various other non-governmental
6 6
organizations. c addition, 8
In
14-1 through the Colorado River Management Work Group, and
. Reclamation worked with various non-governmental organizations
other mechanisms,
No
during the NEPA process. Specifically, Reclamation met with members of the
organizations noted in Table S-2 at their request to discuss environmental and technical
issues.
S.5.6 MEXICO CONSULTATION
Pursuant to an international agreement for mandatory reciprocal consultations, the
United States section of the IBWC (USIBWC) is consulting with Mexico regarding the
proposed interim surplus criteria. Reclamation has assisted USIBWC in conducting this
consultation by providing information on the proposed interim surplus criteria and by
participating in briefings with the Mexico Section of the IBWC and the Mexico
National Water Commission. Meetings with representatives of Mexico were conducted
in April and May 2000, at which representatives of Mexico provided their concerns
regarding the potential effects of the interim surplus criteria. Coordination with
Mexico during the DEIS review phase has consisted of several letters from the
government of Mexico and public agencies in Mexico, which are reproduced in Volume
III of the DEIS.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
34

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EXECUTIVE SUMMARY

Discussion with Mexico took place on November 14, 2000 concerning comments from
Mexico. There was understanding that the consultation with Mexico through IBWC in
the form of technical working groups will continue a forum for technical discussion to
carry out, in the context of international comity, joint cooperation projects in support of
the Colorado River riparian ecology to the Gulf of California that could have a benefit
to the United States and Mexico.
Executive Order 12114 instructs Federal agencies to investigate the effects of Federal
actions in other countries. Reclamation has analyzed and documented the effects of the
proposed interim surplus criteria on natural resources in Mexico. This analysis will
provide an analytical tool for identifying those potential impacts that extend across the
international border and affect Mexico’s natural and physical environment. This
approach is fully consistent with CEQ guidance on NEPA analyses for transboundary
impacts, dated July 1, 1997.
S.5.7 SUMMARY OF COORDINATION CONTACTS
Table S-2 lists the agencies and organizations with which Reclamation coordinated
through meetings and other personal contacts during the scoping and preparation period
of this FEIS.

ior
Inter 17
S.5.8 FEDERAL REGISTER NOTICES
0
f the
pt. o er 29, 2
e
v. D
Table S-3 lists the Federal Register Notices issued to inform the public about the
emb
tion n
aalternativesNovthe preparation and availability
formulation of interim surplus ajo N
v criteria ed o and
of the DEIS. In addition N the notices issued, notices will be provided following the
in to a 4, archiv
cited to 86
publication of this FEIS16announce its availability and the Secretary’s ROD based on
14this FEIS.
No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

The probability of Lake Powell being full in
2016 is 27%.

3

Reservoir water levels exhibit a gradual
declining trend during the interim surplus criteria
period as a result of increasing Upper Division
states consumptive use. The median water
surface elevation in 2016 is 3665 feet msl.

Baseline Conditions/No Action

2

Basin States
Flood Control
Six States
California
Shortage Protection

3664 feet msl
3664 feet msl
3664 feet msl
3660 feet msl
3659 feet msl

Median Elevations in 2016 for each of the alternatives are as
follows:

Effects of Alternatives

37

Flows downstream of Hoover Dam are
governed by downstream demand or Hoover
Dam flood control releases.

Flows downstream of Glen Canyon Dam would
be managed in accordance with the 1995 Glen
Canyon Dam EIS and the 1996 ROD.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Glen Canyon and Hoover Dam
releases and flows downstream of
Lake Mead.

River Flows

continue to decline, although at a lower rate,
due to less frequent Lower Basin surplus
deliveries.

After 2016, median levels stabilize, then rise
and fall slightly, due to 602(a) storage
requirements and less frequent equalization
releases.

Other alternatives: Flows below Glen Canyon Dam would be
similar to baseline conditions. Flows from Hoover Dam to
Parker Dam would be moderately higher until 2016 because of
surplus deliveries. After 2016, flows would be similar to
baseline conditions.

After 2016, median surface elevations continue to decline. By
about 2035, all alternatives converge to elevations similar to
baseline conditions.
Flood Control Alternative: Similar to baseline conditions.

After 2016, Lake Powell water levels under all five alternatives
tend to stabilize similar to baseline conditions. Water levels
under the Basin States, Flood Control, Six States, California
and Shortage Protection alternatives tend to converge with the
baseline conditions by about year 2030.

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on NovMedian Elevations in 2016 for each of the alternatives are as
Lake Mead Water Surface
Reservoir water levels exhibit a gradual
N
Elevations
declining trend during the interim d
vajo Lower Basin surplus criteria follows:
e consumptive
Na
in exceeding long-termhiv The median
Potential changes in Lake Mead waterd period as a result of rc
1143 feet msl
a
Basin States
surface elevations.
1162 feet msl
cite use16864, ininflow. is 1162 feet
Flood Control
water
1146 feet msl
4- surface elevation 2016
Six States
1 msl.
1131 feet msl
California
No. After 2016, median water surface elevations
1130 feet msl
Shortage Protection

Potential changes in Lake Powell
water surface elevations.

Lake Powell Water Surface
Elevations

Reservoirs Elevations and River Flows

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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2002 through 2016
2017 through 2050
2002 through 2016
2017 through 2050
2002 through 2016
2017 through 2050

2002 through 2016
2017 through 2050

Normal:

Surplus:

Shortage:
Normal:

0%
0%

47%
21%

100%
100%

Baseline Conditions/No Action

2

Other Alternatives: Greater probability of surplus through 2016.
The probability is similar to baseline conditions from 2017
through 2050. Deliveries less than the normal apportionment
(4.4 mafy) do not occur under the alternatives at any time
through 2050.

Flood Control Alternative: Similar to baseline conditions.

Effects of Alternatives

100%
100%

2002 through 2016
2017 through 2050
2002 through 2016
2016 through 2050
2002 through 2016
2017 through 2050

Normal:

Surplus:

Shortage:

38

< 4%
50%

Shortage: 2002 through 2016
2017 through 2050

0%
0%

26%
19%

47%
21%

50%

>96%
50%

2002 through 2016
2017 through 2050

Surplus:

2017 through 2050

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Probabilities of meeting Treaty delivery
obligations.

Mexico Treaty Delivery

Probabilities of normal, surplus and
4
shortage conditions.

4

Arizona Water Supply

The Flood Control Alternative would provide slightly higher
(1%) probabilities of surplus than under baseline conditions
through 2016. The rest of the alternatives provide slightly
lower (3% to 7%) probabilities of surplus through 2016 and
about the same level as baseline through 2050. Deliveries
less than the treaty apportionment (1.5 mafy) do not occur
under the alternatives at any time through 2050.

Other Alternatives: Greater probability of surplus through 2015;
same as baseline from 2017 to 2050. The probability of
shortage condition deliveries is slightly higher (7% to 14%) for
the alternatives through 2016. From 2017 to 2050, the
probability of shortage condition deliveries is higher (3% to 5%)
under the alternatives.

Flood Control Alternative: Similar to baseline conditions.

ior
Inter 17 of surplus through 2016
Probabilities of normal, surplus and
Other Alternatives: Greater probability
he
shortage conditions.
under the California and Shortage Protection alternatives and
of tlower (26%) under0 Basin States and Six States
Surplus:
2002 through 2016
29%
t.
2 ,2
2017 through 2050
21% e
D p slightly berThe 9 theof surplus under the alternatives is
alternatives.
probability
v.
em
to
tion < n Novabout the same as baseline from 2017the 2050. The probability
Shortage: 2002 through 2016
4%
of shortage condition deliveries under
alternatives is slightly
jo Na2050ed o50%
2017 through
higher (7% to 14%) through 2016. From 2017 to 2050, the
Nava archiv
probability of shortages under the alternatives is similar to
in
baseline conditions.
cited 16864,
14
No. Normal: 2002 through 2016
96%
Nevada Water Supply
Flood Control Alternative: Similar to baseline conditions.

Probabilities of normal, surplus and
4
shortage conditions.

California Water Supply

Water Supply

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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Increased potential for lower Lake Mead levels
and increased inflow channel lengths under
baseline projections could increase potential of
elevated contaminant concentrations.

Baseline projections assume compliance with
numeric criteria along the river. The Basin
States are committed to meeting the numeric
criteria.

Baseline Conditions/No Action

2

The alternatives, except the Flood Control Alternative, result in
slightly increased potential for increased contaminant
concentrations in Boulder Basin, due to greater potential for
lower Lake Mead levels than under baseline conditions.

Modeling indicates potential for slight reductions in salinity
under each alternative as compared to baseline.

Effects of Alternatives

39

Species are adapted to fluctuating reservoir
levels. Therefore, increased potential for lower
Lake Mead and Lake Powell surface levels is
not expected to adversely affect aquatic
species.

Average annual probability from 2002 through
2016:
Davis Dam
9%
Parker Dam
10%
Average annual probability from 2017 through
2050:
Davis Dam
5%
Parker Dam
6%

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential effects on Lake Mead and
Lake Powell fisheries and associated
aquatic habitat.

Lake Habitat and Sport Fisheries

Aquatic Resources

Probability of damaging flows below
Davis and Parker Dams.

Flooding Downstream of Hoover
Dam

Glen Canyon Dam.

Compared with baseline conditions, slightly increased potential
for higher reservoir levels under the Flood Control Alternative
and increased potential for lower reservoir levels under the
other alternatives would not be expected to result in substantial
changes to lake habitat.

The probability under other alternatives is slightly less than
under baseline conditions.

The probability under the Flood Control Alternative is slightly
greater than under baseline conditions.

ior
Inter 17
Flow-Related Issues
the
2
ofprobability 29, the 0
t.
Beach/Habitat-Building Flow
The average annual probability of BHBF
r under during the is typically less than
Dep Thembaseline conditionsalternativesinterim period, and
Releases
releases is 16% through 2016 and 14% from
under be
v.
e
tion n Novconverges with baseline conditions thereafter.
Probability of BHBF release conditions 2017 through 2050.
Na d o
from Glen Canyon Dam.
jo
Nava archive
in
Low Steady Summer Flows
annual
t requisite864 probability flows is 38% under baseline under the during the is seven less and
cifored The averagelow,steady summerof conditions The probability conditionsalternativesfirsttypicallyyearsthan
for
6 2016 and 62% from 2017 through
Probability of requisite conditions
4-1
similar to or slightly greater than under baseline conditions
low steady summer flow releaseso. 1 through
from
2050.
thereafter.
N

Contaminant concentrations in Boulder
Basin of Lake Mead, in proximity to the
SNWS intakes at Saddle Island.

Lake Mead Water Quality and Las
Vegas Water Supply

Potential change in salinity below
Hoover Dam.

Colorado River Salinity

Water Quality

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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Under baseline conditions, increased potential
over time for lower reservoir levels could
increase potential for development of temporary
riparian habitat at the deltas, which would
benefit special-status wildlife species that utilize
such habitat.

Under baseline conditions, special-status plant
species would continue to be affected by
fluctuating water levels, which would
periodically expose and inundate areas where
the plants occur.

Baseline Conditions/No Action

2

The Flood Control Alternative would have slightly lower
potential, while the other alternatives would have increased
potential, for lower reservoir elevations and associated potential
increases in delta habitat.

Although reservoir elevations would differ, the effects of all
alternatives would be similar to baseline conditions.

Effects of Alternatives

40

Baseline condition projections indicate an
increased potential for the occurrence of lower
Lake Mead and Lake Powell reservoir levels,
which may result in potential increases in
navigation hazards and decreased safe boating
capacity (due to decreased reservoir surface
area).

operating range that some existing facilities
may be able to accommodate. Such
occurrence would likely result in modification of
facilities to accommodate lower surface
elevations.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential effects on reservoir boating
that may result from changes in Lake
Mead and Lake Powell surface
elevations.

Reservoir Boating/Navigation

recreation facilities from changes in
Lake Mead and Lake Powell surface
elevations.

The Flood Control Alternative has slightly lower potential, and
each of the other alternatives have higher potential, for each of
navigation hazards and reduced carrying capacity.

ior
Inter 17
e
of th 29, 20
pt.
er
. De Changes in potential for lower reservoir levels under the various
Special-Status Fish
Under baseline conditions, increased potential
n v have ovalternatives would not change potential for effects.
emb
tio
for lower elevations is not expected to
N
Potential effects of Lake Mead and
jo Na ved different
effects on special-status species fish on
aoccur at present.
Lake Powell reservoir level changes
v
than Na that
on special-status fish species.
in those 4, archi
Recreation
cited 1686
Reservoir Marinas/Boat Launching 14Baseline condition projections indicate
The Flood Control Alternative has a slightly decreased potential
No. increased potential for reservoir levels lower for lower reservoir levels; each of the other alternatives have
Potential effects on shoreline
than those considered within the normal
increased potential for lower levels and necessary relocations.

Potential effects on special-status
wildlife species associated primarily
with potential effects on riparian
habitat at the Lake Mead and Virgin
River deltas, and the lower Grand
Canyon.

Special-Status Wildlife

Potential effects on special-status
plants for areas influenced by Lake
Powell and Lake Mead water levels.

Special-Status Plants

Special-Status Species

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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Baseline condition projections indicate
increased relocation costs associated with
future increased potential for lower reservoir
levels.

Potential effects on sport fisheries are minimal
under baseline conditions.

Boaters may have reduced take-out
opportunities due to increased potential for
lower reservoir surface elevations.

Baseline Conditions/No Action

2

The Flood Control Alternative is similar to baseline conditions.
Other alternatives have greater potential for increased
relocation costs, based on an average cost per foot associated
with relocating facilities.

Changes in reservoir elevations under each of the alternatives
would not be expected to adversely affect sport fisheries or
fishing in either reservoir.

The Flood Control Alternative has lower potential, and each of
the other alternatives have increased potential, for reduced
take-out opportunities resulting from lower reservoir elevations.

Effects of Alternatives

41

Future lower average Lake Mead water levels
would require more energy and increased
pumping costs for the SNWS intake.

4685 GWh through 2016; 3903 GWh from 2017
through 2050.

production:

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential change in the cost of power
to pump Lake Mead water through the
SNWS.

Pumping Power Needs for SNWS

Increased costs associated with
relocating shoreline facilities to remain
in operation at lower reservoir
elevations.

Basin States
Flood Control
Six States
California
Shortage Protection

$229,395
$ 32,685
$214,779
$544,843
$532,635

The increase over baseline conditions of annual pumping costs
for each alternative follows:

production is from 51 to 127 GWh less.

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
Energy Resources
ation on Nov
N average annual
Hydroelectric Power Production
Glen Canyonajo
The Flood Control Alternative is similar to baseline conditions.
v Powerplanthived
energy production:
Na
c
Potential for changes in energy
Average annual power production under the other alternatives
in
ar
production at Glen Canyon and ited 4532 GWh64, 2016; 4086 GWh from 2017 is greater than under baseline conditions for the first six to eight
through
c
6 2050.
Hoover powerplants.
through 8
years, then is less for the remaining years. Averaged from
14-1 Powerplant average annual energy
2002 to 2050, Glen Canyon annual power production is from 12
o. Hoover
N
to 30 GWh less than baseline conditions, while Hoover power

Recreation Facilities Relocation
Costs

Potential effects on sport fishing in
Lake Mead and Lake Powell.

Reservoir Sport Fishing

Potential effects on river boating at
Lake Powell and Lake Mead inflow
areas.

River and Whitewater Boating

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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Future lower average Lake Powell water levels
would require more energy and increased
pumping costs for the Navajo Generating
Station and the City of Page.

Intake Energy Requirements at Lake
Powell

2

The increase over baseline conditions of annual pumping costs
for each alternative follows:
Navajo Generating Station
$2,216
Basin States
$
0
Flood Control
$2,129
Six States
$4,651
California
$4,660
Shortage Protection

Effects of Alternatives

42

Not significant due to past water level
fluctuations. Impacts have already occurred.

Increased probability of temporary degradation
in visual attractiveness of shoreline vistas
resulting from increasing potential for lower
water levels in Lake Mead and Lake Powell.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Effects on Historic Properties in
Operational Zone of Reservoir and
River Reaches.

Cultural Resources

Potential effects of lower reservoir
elevations on scenic quality.

Visual Attractiveness of Reservoir
Scenery, Lake Mead and Lake
Powell

Visual Resources

Not significant due to past water level fluctuations. Impacts
have already occurred.

Other alternatives: Higher probability of degradation of visual
attractiveness through 2016 due to accelerated decline of
minimum reservoir levels.

Flood Control Alternative: Same as baseline conditions.

City of Page
Basin States
Flood Control
Six States
California
Shortage Protection

ior $ 529
Inter 17 $ 0
e
of th 29, 20 $ 508
$1,110
pt.
$1,112
. De ember
v
Air Quality
tion n Nov
a
Fugitive Dust Emissions from
Increased potential for lower reservoir levels
Slightly decreased shoreline exposure under Flood Control
ajo N ived o
Nav arc for
Exposed Reservoir Shoreline
would increase potential h shoreline exposure
Alternative would lower fugitive dust emission potential. Other
in baseline ,
4would be minimal due to low increased fugitive have slightly increased changes in
Potential for fugitive dust emissionse
it d underemissions conditions. Increases in fugitive alternatives woulddust emissions. Minimalpotential for areac
86
from shoreline exposure at Lake Mead dust 6
4-1 potential of shoreline.
emission
wide fugitive dust emissions would be expected.
1
and Lake Powell.
No.

Potential change in the cost of power
to pump Lake Powell water to the
Navajo Generating Station and the
City of Page.

Baseline Conditions/No Action

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

Case: 14-16864, 12/04/2017, ID: 10675851, DktEntry: 131-2, Page 46 of 1200

No effects are anticipated.

There is a probability of shortages of CAP
priority water for tribes in central Arizona.

The water available to members of Ten Tribes
Partnership would not be affected by future
changes under baseline conditions.

Baseline Conditions/No Action

2

No effects anticipated.

Greater probability of shortages of CAP priority water for tribes
in central Arizona under all alternatives with the exception of the
Flood Control Alternative.

No effect on water available to members of Ten Tribes
Partnership.

Effects of Alternatives

Under the Basin States Alternative there would be no effect on
desert pupfish, Vaquita, Yuma clapper rail, California black rail,
Clarks grebe; and there is not likely to be any adverse affect on
totoaba, Southwestern willow flycatcher, Yellow-billed cuckoo,
Elf owl or Bell's vireo.

Other alternatives: Small reduction in probability of excess
flows.

43

Effects identified are based on probabilities developed through modeling of possible future conditions through 2050, discussed in detail in Chapter 3.
In general, the differences between the alternatives and baseline conditions would be greatest at or near 2016, the year in which the interim surplus criteria would
terminate.
Lake Powell is considered to be essentially full when the lake elevation reaches 3695 feet msl (5 feet below the top of the spillway gates).
Probabilities of shortage are based on the modeling assumption of protecting a Lake Mead elevation of 1083 feet msl. There are no established shortage criteria for the
operation of Lake Mead.

Probability of excess flows below Morelos Dam
would gradually decline.

would gradually decline under baseline
conditions.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

3.
4.

1.
2.

Potential Effects on Species and
Habitat in Mexico

Amount of excess flow that may reach
the Colorado River delta.

ior
Inter 17
Transboundary Effects
the
ofFlood Control9, 20 would provide slightly higher (1%)
.
Normal:
2002 through 2016
100% ept The
Treaty Water Delivery Obligations
er 2 Alternative
.D
2017 through 2050
100%
probabilities of surplus than under baseline conditions 2016.
v
mbof the alternatives provide slightly lower (3% to 7%)
Probabilities of meeting Treaty delivery
e
tion 26%
obligations
Na2016 d on NovThe rest of surpluses through 2016 and about the same
Surplus:
2002 through
probabilities
ajo 2050
level as baseline through 2050. Deliveries less than the treaty
Nav2016 throughhive 19%
in
apportionment (1.5 mafy) do not occur under the alternatives at
d Shortage: 62002 through 2016
, arc
4
0%
any time through 2050.
cite 168 2017 through 2050
0%
4. 1 Probability of excess flows below Morelos Dam Flood Control Alternative: Similar to baseline.
Flow Below Morelos Dam No

Exposure of Minority or Low Income
Communities to Health or
Environmental Hazards

Environmental Justice

Effects on water supply for Indian
Tribes and Communities

Indian Trust Assets

Resource/Issue

Table S-1
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

EXECUTIVE SUMMARY

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Case: 14-16864, 12/04/2017, ID: 10675851, DktEntry: 131-2, Page 48 of 1200
EXECUTIVE SUMMARY

Table S-2
Participants with Reclamation Regarding the Interim Surplus Criteria
Environmental Impact Statement Process
Agency or Organization Invited to or Requesting
Meetings

Meetings

Federal Agencies
National Park Service – Cooperating Agency

Various plan formulation and evaluation meetings

U. S. Section of the International Boundary and Water
Commission – Cooperating Agency

Various plan formulation and evaluation meetings;
Briefings for Mexico

Bureau of Indian Affairs

5/26/99, 12/15/99, 1/21/00, 2/24/00, 8/30/00

Environmental Protection Agency

6/15/99, 8/30/00

Fish And Wildlife Service

Geological Survey

Various Consultation Meetings on ESA
Compliance
Consultation on Special Status Species in the Sea
of Cortez, 10/12/00
6/15/99, 8/15/00

Western Area Power Administration

6/15/99, 8/15/00

National Marine Fisheries Service

ior
Inter 17
0
f the
pt. o er 29, 2
Chemehuevi Tribe (10 Tribes member)
5/26/99, 6/15/99, 11/16/1999, 12/15/99,
e
v. D & 25/00,b
2/24
m 8/4/00
ation on Nove
N
Cocopah Indian Tribe (10 Tribes member)
vajo
ed 5/26/99, 6/15/99, 111/16/1999, 2/15/99,
in Na 4, archiv
2/24 & 25/00, 8/3/00
d
cite 1686
Colorado River Indian Tribes - Tribes member)
5/26/99, 6/15/99, 11/16/1999, 12/15/99,
14 (10
No.
2/24 & 25/00, 8/4/00

Tribal Coordination – Ten Tribes Partnership

Fort Mojave Indian Tribe (10 Tribes member)

5/26/99, 6/15/99, 11/16/1999, 12/15/99,
2/24 & 25/00, 8/2/00

Jicarilla Apache Tribe (10 Tribes member)

5/26/99, 11/16/1999, 12/15/99, 2/24 & 25/00

Navajo Nation (10 Tribes member)

5/26/99, 11/16/1999, 12/15/99, 2/24 & 25/00,
9/27/00, 8/3/00

Northern Ute Tribe (10 Tribes member)

5/26/99, 11/16/1999, 12/15/99, 2/24 & 25/00,
8/17/00

Quechan Indian Tribe (10 Tribes member)

5/26/99, 6/15/99, 11/16/1999, 12/15/99,
2/24 & 25/00, 8/2/00

Southern Ute Indian Tribe (10 Tribes member)

5/26/99, 11/16/1999, 12/15/99, 2/24 & 2500

Ute Mountain Ute Tribe (10 Tribes member)

5/26/99, 11/16/1999, 12/15/99, 2/24 & 25/00,
8/3/00

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
44

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EXECUTIVE SUMMARY

Table S-2
Participants with Reclamation Regarding the Interim Surplus Criteria
Environmental Impact Statement Process
Agency or Organization Invited to or Requesting
Meetings

Meetings

Tribal Coordination –Tribes And Communities In Central Arizona
Ak-Chin Indian Community

5/26/99, 6/15/99, 1/21/00, 8/3/00

Mojave-Apache Tribe

5/26/99, 1/21/00, 8/3/00

Gila River Indian Community

5/26/99, 6/15/99, 1/21/00, 8/3/00

Pasqua-Yaqui Tribe

5/26/99, 1/21/00

Salt River Pima-Maricopa Indian Community

5/26/99, 6/15/99, 1/21/00

San Carlos Indian Tribe

5/26/99, 6/15/99, 1/21/00, 8/3/00

Tohono O’Odham Tribe

5/26/99, 6/15/99, 1/21/00, 8/15/00, 8/3/00

Tonto Apache Tribe

5/26/99, 6/15/99, 1/21/00, 8/4/00

Yavapai-Apache Indian Community

5/26/99, 6/15/99, 1/21/00, 8/3/00

Yavapai-Prescott Indian Tribe

5/26/99, 6/15/99, 1/21/00

Morongo Band of Mission Indians

8/30/00

Torres-Martinez Desert Cahuilla Tribe

1/21/00, 8/30/00

Twenty-Nine Palms Band of Mission Indians

[Contact attempted; DEIS sent]

ior
Inter 17
0
f the
pt. o er 29, 2
e Indians
Tribal Coordination – Coachella Valley Consortium Of.Mission
v D v mb
ation on8/30/00,e9/6/00
No
Agua Caliente Band of Cahuilla Indians jo N
va
ed
in Na
rchiv
Augustine Band of Mission Indians 64, a
[Contact attempted; DEIS sent]
ited 68
c
4-1
Cabazon Band of Mission1
(Contact attempted; DEIS sent]
No. Indians

Tribal Coordination – Other Tribes
Havasupai Indian Tribe

6/15/99, 5/26/99, 1/21/00

Hopi Tribe

6/15/99, 5/26/99, 1/21/00, 8/4/00

Hualapai Nation

6/15/99, 5/26/99, 1/21/00, 8/3/00

Kaibab Paiute Tribe

8/3/00

San Juan Southern Paiute Tribe

8/3/00

San Luis Rey Indian Water Authority

8/16/00

Zuni Indian Tribe

8/3/00

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
45

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EXECUTIVE SUMMARY

Table S-2
Participants with Reclamation Regarding the Interim Surplus Criteria
Environmental Impact Statement Process
Agency or Organization Invited to or Requesting
Meetings

Meetings

State and Local Water and Power Agencies
Arizona Department of Water Resources

6/15/99, 12/16/1999,

Central Arizona Water Conservancy District

6/15/99, 8/15/00

Coachella Valley Water District

6/15/99, 6/6/00, 8/15/00

Colorado River Board of California

6/15/99, 12/16/1999, 6/6/00, 8/15/00,11/14/00

Colorado River Commission of Nevada

6/15/99, 12/16/1999,

Colorado River Water Conservation District

8/15/00

Colorado Water Conservation Board

12/16/99, 8/15/00

Utah Division of Water Resources

12/16/99,

Imperial Irrigation District

6/15/99, 6/6/00, 8/15/00, 11/14/00

Las Vegas Valley Water District

6/22/99

Upper Colorado River Commission

6/15/99, 8/15/00

San Diego County Water Authority

8/15/00

Southern Nevada Water Authority

12/16/99, 8/15/00

ior
Inter 17
f the 9, 0
Metropolitan Water District, California
6/15/99,o
pt. 6/6/00, 8/15/00 2
De
er 2
n v. 12/16/99,mb
New Mexico Interstate Stream Commission
atio
Nove 8/15/00
ajo N ived on
Nav
Office of the State Engineer, iWyoming
12/16/99, 8/15/00
d n 64, arch
te
ciResources68
Parker Valley Natural
12/16/99,
-1 Conservation D.
o. 14
N

Non-Governmental Agencies
Center for Biodiversity

12/15/99, 6/8/00

Defenders of Wildlife

12/15/99, 8/15/00

Environmental Defense

12/15/99, 8/15/00

Glen Canyon Action Network

8/22/00

Pacific Institute

12/15/99, 8/15/00

Southwest Rivers

12/15/99, 8/15/00

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
46

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EXECUTIVE SUMMARY

Table S-2
Participants with Reclamation Regarding the Interim Surplus Criteria
Environmental Impact Statement Process
Agency or Organization Invited to or Requesting
Meetings

Meetings

International Agencies
International Boundary and Water Commission, Mexico
Section

4/12/00, 5/11 & 12/2000, 9/30/00, 11/9/00,
11/14/00

National Water Commission, Mexico

4/12/00, 5/11 & 12/2000, 9/30/00, 11/9/00,
11/14/00

National Institute of Ecology, Mexico

4/12/00, 9/30/00, 11/9/00, 11/14/00

Secretariat of Environment, Natural Resources and Fish,
Mexico

9/30/00, 11/14/00

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
47

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Table S-3
Federal Register Notices Regarding Interim Surplus Criteria
Notice

Title

Volume 64, No. 95,
Page 27008, May 18,
1999

Intent to Solicit Comments on the Development of Surplus Criteria for
Management of the Colorado River and to Initiate NEPA Process.

Volume 64, No. 103,
Page 29068, May 28,
1999

Public Meetings on the Development of Surplus Criteria for Management
of the Colorado River and to Initiate NEPA Process

Volume 64, No. 234,
Page 68373, December
7, 1999

Colorado River Interim Surplus Criteria; Notice of Intent to Prepare an
Environmental Impact Statement

Volume 65, No. 131,
Page 68373, July 7,
2000

Notice of availability of a draft environmental impact statement and public
hearings for the propose adoption of Colorado River Interim Surplus
Criteria

Volume 65, No. 149,
Page 47516, August 2,
2000

Notice of revised dates for public hearings on the proposed adoption of
Colorado River Interim Surplus Criteria

Volume 65, No. 153,
Page 48531, August 8,
2000

Notice of public availability of information submitted on a draft
environmental impact statement for the proposed adoption of Colorado
river Interim Surplus Criteria (Colorado River Basin States: Interim
Surplus Guidelines – Working Draft)

ior
Inter 17
0
f the
pt. o er 29, 2
e
Volume 65, No. 185,
Notice of correction to n v. D Federal Register notice of availability
published
mb
Page 57371,
(Colorado River Basin States: Interim Surplus Guidelines – Working Draft)
atio on Nove
jo N
September 22, 2000
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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ior
Inter 17
the
t. of r 29, 20
Dep mbe
n v.
tio
ove
jo Na ved on N
va
in Na 4, archi
cited 1686
o. 14
N

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erior
e Int 017
2
of th
ept. ber 29,
.D
v
tion
ovem
o Na ed on N
vaj
in Na 4, archiv
cited 1686
14No.

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ior
Inter 17
e
20
of th
ept. ber 29,
.D
v
tion
ovem
o Na ed on N
j
iv
Nava
d in 64, arch
ite
c
-168
o. 14
N

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ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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TABLE OF CONTENTS
VOLUME I
1

INTRODUCTION AND BACKGROUND......................................................................1-1
1.1
1.1.1
1.1.2
1.1.3
1.1.4
1.1.5

INTRODUCTION ..............................................................................................1-1
Proposed Federal Action ..............................................................1-2
Background...................................................................................1-2
Purpose of and Need for Action ...................................................1-3
Relationship to the United States-Mexico Water Treaty..............1-4
Lead and Cooperating Agencies...................................................1-4

1.2

SUMMARY OF CONTENTS OF THIS FEIS...................................................1-5

1.3
WATER SUPPLY MANAGEMENT AND ALLOCATION ............................1-6
1.3.1
Colorado River System Water Supply..........................................1-6
1.3.2
Apportionment of Water Supply ..................................................1-8
1.3.2.1
The Law of the River ....................................................................1-8
1.3.2.2
Apportionment Provisions..........................................................1-10
1.3.2.2.1
Upper Division State Apportionments .......................................1-12
ior
1.3.2.2.2
Lower Division State Apportionments .......................................1-13
Inter 17
0
f the
1.3.2.2.3
Mexico Apportionment ..............................................................1-15
pt. o er 29, 2
eCriteria ..................................................1-15
1.3.3
Long-Range Operating
v. D
mb
ation PlanNove
1.3.4
Annual Operating on ...............................................................1-16
oN
avaj chive and
1.3.4.1
NNormal,rSurplusd Shortage Determinations ..........................1-16
in
a
1.3.5
cited 16System Reservoirs and Diversion Facilities ...............................1-17
864,
14- Flood Control Operation.............................................................1-20
1.3.6
No.
1.3.7
Hydropower Generation .............................................................1-21
1.4
RELATED AND ONGOING ACTIONS.........................................................1-22
1.4.1
California’s Colorado River Water Use Plan .............................1-22
1.4.1.1
Imperial Irrigation District/San Diego County Water
Authority Water Transfer ...........................................................1-23
1.4.1.2
All-American and Coachella Canal Lining Projects ..................1-23
1.4.2
Glen Canyon Dam Operations....................................................1-24
1.4.2.1
Adaptive Management Program.................................................1-25
1.4.2.2
Beach/Habitat-Building Flows and Beach/HabitatMaintenance Flows.....................................................................1-25
1.4.2.3
Temperature Control at Glen Canyon Dam................................1-26
1.4.3
Actions Related to the Biological and Conference Opinion
on Lower Colorado River Operations and Maintenance ............1-26
1.4.4
Lower Colorado River Multi-Species Conservation
Program ......................................................................................1-27
1.4.5
Secretarial Implementation Agreement Related To
California’s Colorado River Water Use Plan .............................1-28

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

1.4.6

1.5
2

Offstream Storage of Colorado River Water and
Development and Release of Intentionally Created Unused
Apportionment In The Lower Division States ...........................1-28
DOCUMENTS INCORPORATED BY REFERENCE ...................................1-28

DESCRIPTION OF ALTERNATIVES............................................................................2-1
2.1

INTRODUCTION ..............................................................................................2-1

2.2
DEVELOPMENT OF ALTERNATIVES ..........................................................2-1
2.2.1
Operating Strategies for Surplus Determination ..........................2-1
2.2.1.1
The R Strategy..............................................................................2-1
2.2.1.2
The A Strategy..............................................................................2-1
2.2.1.3
The P Strategy ..............................................................................2-2
2.2.1.4
Flood Control Strategy .................................................................2-2
2.2.2
Origins of the California, Six States, and Basin
States Alternatives ........................................................................2-2
2.2.3
Pacific Institute Proposal ..............................................................2-3
2.2.4
Formulation of Alternatives .........................................................2-4
2.2.5
Utilization of Proposals from the Basin States.............................2-5
2.2.6
No Action Alternative and Baseline Condition............................2-6
erior

e Int

2.3
DESCRIPTION OF ALTERNATIVES..............................................................2-6
of th 29, 2017
pt.BaselinerCondition............................2-7
D
e
2.3.1
No Action Alternative e
n v. and emb
2.3.1.1
Approach atiSurplusn NovDetermination ..................................2-7
to o o Water
oN
avaj rchi ed
2.3.1.2
N70R BaselinevSurplus Triggers .....................................................2-8
in
a
2.3.2
cited 16Basin States Alternative (Preferred alternative) .........................2-10
864,
2.3.2.1 o. 14- Approach to Surplus Water Determination ................................2-11
2.3.2.2 N
Basin States Alternative Surplus Triggers..................................2-11
2.3.2.1.1
Basin States Alternative Tier 1 (70R).........................................2-14
2.3.2.1.2
Basin States Alternative Tier 2 (1145 feet msl) .........................2-14
2.3.2.1.3
Basin States Alternative Tier 3 (1125 feet msl) .........................2-14
2.3.2.2
Draft Guidelines .........................................................................2-14
2.3.3
Flood Control Alternative...........................................................2-14
2.3.3.1
Approach to Surplus Water Determination ................................2-14
2.3.3.2
Flood Control Alternative Surplus Triggers...............................2-15
2.3.4
Six States Alternative .................................................................2-15
2.3.4.1
Approach to Surplus Water Determination ................................2-15
2.3.4.2
Six States Alternative Surplus Triggers......................................2-18
2.3.4.2.1
Six States Alternative Tier 1 (70R) ............................................2-18
2.3.4.2.2
Six States Alternative Tier 2 (1145 feet msl) .............................2-19
2.3.4.2.3
Six States Alternative Tier 3.......................................................2-19
2.3.5
California Alternative .................................................................2-19
2.3.5.1
Approach to Surplus Water Determination ................................2-19
2.3.5.2
California Alternative Surplus Triggers .....................................2-19
2.3.5.2.1
California Alternative Tier 1 ......................................................2-20

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

2.3.5.2.2
2.3.5.2.3
2.3.6
2.3.6.1
2.3.6.2
2.4
3

California Alternative Tier 2 ......................................................2-20
California Alternative Tier 3 ......................................................2-20
Shortage Protection Alternative..................................................2-22
Approach to Surplus Water Determination ................................2-22
Surplus Triggers .........................................................................2-22

SUMMARY TABLE OF IMPACTS................................................................2-22

AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES........3.1-1
3.1
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.1.6

INTRODUCTION ...........................................................................................3.1-1
Structure of Resource Sections..................................................3.1-1
Use of Modeling to Identify Potential Future Colorado
River System Conditions ...........................................................3.1-1
Baseline Conditions...................................................................3.1-2
Impact Determination................................................................3.1-2
Period of Analysis .....................................................................3.1-2
Environmental Commitments....................................................3.1-2

3.2
POTENTIALLY AFFECTED AREA .............................................................3.2-1
3.2.1
Colorado River Segments and Issues Addressed ......................3.2-1
3.2.1.1
Lake Powell ...............................................................................3.2-3
ior
Inter Lake Mead ...........3.2-3
3.2.1.2
Colorado River from Glen Canyon Dam to 017
f the
pt. o er 29, 2
3.2.1.3
Lake Mead .................................................................................3.2-3
. De
b
3.2.1.4
Colorado Rivern v Hoover m to the Southerly
io from NoveDam
at
oN
on
International Boundary..............................................................3.2-4
avaj r
NAdaptive chived
in
3.2.2
a Management Program Influence on Glen
cited 16Canyon Dam Releases ...............................................................3.2-5
864,
4-

o. 1

N
3.3
RIVER SYSTEM OPERATIONS ...................................................................3.3-1
3.3.1
Operation of the Colorado River System ..................................3.3-1
3.3.1.1
Operation of Glen Canyon Dam................................................3.3-2
3.3.1.2
Operation of Hoover Dam .........................................................3.3-3
3.3.2
Natural Runoff and Storage of Water........................................3.3-6
3.3.3
Modeling and Future Hydrology ...............................................3.3-9
3.3.3.1
Model Configuration .................................................................3.3-9
3.3.3.2
Interim Surplus Criteria Modeled..............................................3.3-9
3.3.3.3
General Modeling Assumptions ..............................................3.3-10
3.3.3.4
Lake Mead Water Level Protection Assumptions...................3.3-12
3.3.3.5
Computational Procedures.......................................................3.3-13
3.3.3.6
Post-Processing and Data Interpretation Procedures...............3.3-14
3.3.4
Modeling Results.....................................................................3.3-15
3.3.4.1
General Observations Concerning Modeling Results .............3.3-15
3.3.4.2
Lake Powell Water Levels.......................................................3.3-18
3.3.4.2.1
Dam and Reservoir Configuration...........................................3.3-18
3.3.4.2.2
Historic Water Levels..............................................................3.3-19
3.3.4.2.3
Baseline Conditions.................................................................3.3-19

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

3.3.4.2.4
3.3.4.3
3.3.4.4
3.3.4.4.1
3.3.4.4.2
3.3.4.4.3
3.3.4.4.4
3.3.4.5
3.3.4.5.1
3.3.4.5.2
3.3.4.5.3
3.3.4.5.4

Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.3-25
River Flows Between Lake Powell and Lake Mead................3.3-27
Lake Mead Water Levels.........................................................3.3-29
Dam and Reservoir Configuration...........................................3.3-29
Historic Lake Mead Water Levels...........................................3.3-31
Baseline Conditions.................................................................3.3-31
Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.3-37
Comparison of River Flows Below Hoover Dam ...................3.3-42
River Flows Between Hoover Dam and Parker Dam..............3.3-45
River Flows Between Parker Dam and Palo Verde
Diversion .................................................................................3.3-54
River Flows Between Palo Verde Diversion Dam and
Imperial Dam...........................................................................3.3-63
River Flows Between Imperial Dam and Morelos Dam .........3.3-71

3.4
WATER SUPPLY............................................................................................3.4-1
3.4.1
Introduction ...............................................................................3.4-1
3.4.2
Methodology..............................................................................3.4-1
ior
3.4.3
Affected Environment ...............................................................3.4-1
Inter 17
0
f the
3.4.3.1
Water Use Projection Process....................................................3.4-3
pt. o er 29, 2
e
v. D
3.4.3.2
State of Arizona.........................................................................3.4-3
mb
ation on Nove
3.4.3.3
Statejo N
of California......................................................................3.4-7
ava Nevada........................................................................3.4-12
NState of rchived
3.4.3.4
d in 64, a
3.4.3.5 cite
8
16Upper Basin States ..................................................................3.4-14
. 14- Mexico.....................................................................................3.4-14
3.4.3.6 No
3.4.4
Environmental Consequences..................................................3.4-16
3.4.4.1
State of Arizona.......................................................................3.4-17
3.4.4.1.1
Baseline Conditions.................................................................3.4-17
3.4.4.1.2
Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.4-23
3.4.4.2
State of California....................................................................3.4-26
3.4.4.2.1
Baseline Conditions.................................................................3.4-26
3.4.4.2.2
Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.4-31
3.4.4.3
State of Nevada........................................................................3.4-34
3.4.4.3.1
Baseline Conditions.................................................................3.4-34
3.4.4.3.2
Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.4-38
3.4.4.4
Upper Basin States ..................................................................3.4-41
3.4.4.5
Mexico.....................................................................................3.4-42
3.4.4.5.1
Baseline Conditions.................................................................3.4-42
3.4.4.5.2
Comparison of Surplus Alternatives to
Baseline Conditions.................................................................3.4-47

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3.5
WATER QUALITY.........................................................................................3.5-1
3.5.1
Introduction ...............................................................................3.5-1
3.5.2
Colorado River Salinity.............................................................3.5-1
3.5.2.1
Methodology..............................................................................3.5-1
3.5.2.2
Affected Environment ...............................................................3.5-2
3.5.2.2.1
Historical Data...........................................................................3.5-2
3.5.2.2.2
Regulatory Requirements and Salinity Control Programs ........3.5-3
3.5.2.2.3
General Municipal, Industrial, and Agricultural Effects of
Increased Salinity Concentrations .............................................3.5-6
3.5.2.3
Environmental Consequences....................................................3.5-9
3.5.3
Lake Mead Water Quality and Las Vegas Water Supply..........3.5-9
3.5.3.1
Methodology..............................................................................3.5-9
3.5.3.2
Affected Environment .............................................................3.5-11
3.5.3.2.1
General Description.................................................................3.5-11
3.5.3.2.2
Lake Mead Water Quality and Limnology..............................3.5-16
3.5.3.2.3
Hydrodynamics of Lake Mead and Boulder Basin .................3.5-19
3.5.3.3
Environmental Consequences..................................................3.5-20
3.5.3.3.1
General Effects of Reduced Lake Levels ................................3.5-20
3.5.3.3.1.1
Volume Reduction...................................................................3.5-22
ior
3.5.3.3.1.2
Tributary Water Quality ..........................................................3.5-22
Inter 17
3.5.3.3.2
Comparison of Baseline Conditions and , 20
Alternatives.............3.5-22
f the
pt. o er 29
e
3.5.3.3.2.1
Baseline Conditions.................................................................3.5-23
v. D
mb
3.5.3.3.2.2
Basin StatestiAlternative ..........................................................3.5-23
a on on Nove
oN
3.5.3.3.2.3
avaj chived
NBaselinerConditions.................................................................3.5-25
a
3.5.3.3.2.4 in Basin States Alternative ..........................................................3.5-25
cited 16864,
3.5.3.3.2.5 4- Flood Control Alternative........................................................3.5-25
1
No.
3.5.3.3.2.6
Six States Alternative ..............................................................3.5-25
3.5.3.3.2.7
California Alternative ..............................................................3.5-25
3.5.3.3.2.8
Shortage Protection Alternative...............................................3.5-26
3.5.3.3.2.9
Summary of Changes in Lake Mead Volume and
Elevation..................................................................................3.5-26
3.5.4
Water Quality Between Hoover Dam and Southerly
International Boundary............................................................3.5-26
3.6
RIVERFLOW ISSUES ....................................................................................3.6-1
3.6.1
Introduction ...............................................................................3.6-1
3.6.2
Beach/Habitat-Building Flows ..................................................3.6-1
3.6.2.1
Methodology..............................................................................3.6-2
3.6.2.2
Affected Environment ...............................................................3.6-2
3.6.2.3
Environmental Consequences....................................................3.6-3
3.6.2.3.1
Baseline Conditions...................................................................3.6-5
3.6.2.3.2
Basin States Alternative ............................................................3.6-5
3.6.2.3.3
Flood Control Alternative..........................................................3.6-5
3.6.2.3.4
Six States Alternative ................................................................3.6-5
3.6.2.3.5
California Alternative ................................................................3.6-5

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3.6.2.3.6
3.6.3
3.6.3.1
3.6.3.2
3.6.4
3.6.4.1
3.6.4.1.1
3.6.4.1.2
3.6.4.1.3
3.6.4.1.4
3.6.4.1.5
3.6.4.1.6
3.6.4.2

Shortage Protection Alternative.................................................3.6-6
Low Steady Summer Flow ........................................................3.6-6
Affected Environment ...............................................................3.6-6
Environmental Consequences....................................................3.6-6
Flooding Downstream of Hoover Dam .....................................3.6-8
Affected Environment ...............................................................3.6-9
Hoover Dam to Davis Dam .......................................................3.6-9
Davis Dam to Parker Dam.........................................................3.6-9
Hoover Dam to Davis Dam .....................................................3.6-10
Davis Dam to Parker Dam.......................................................3.6-10
Parker Dam to Laguna Dam ....................................................3.6-10
Laguna Dam to SIB .................................................................3.6-10
Environmental Consequences..................................................3.6-11

3.7
AQUATIC RESOURCES................................................................................3.7-1
3.7.1
Introduction ...............................................................................3.7-1
3.7.2
Lake Habitat ..............................................................................3.7-1
3.7.2.1
Methodology..............................................................................3.7-1
3.7.2.2
Affected Environment ...............................................................3.7-2
3.7.2.2.1
Lake Powell ...............................................................................3.7-2
ior
3.7.2.2.2
Lake Mead .................................................................................3.7-4
Inter 17
the ....................................3.7-4
0
3.7.2.2.3
General Effects of Reservoirof
pt. Operation9, 2
e
r2
3.7.2.3.
Environmental n v. D
Consequences....................................................3.7-5
mbe
atio ...........................................................................3.7-5
Nove
3.7.3
Sportjo N
Fisheries
n
ava rchived o
NMethodology..............................................................................3.7-6
3.7.3.1
d in 64, a
3.7.3.2 cite
8
16Affected Environment ...............................................................3.7-6
. 14- Reservoir Sport Fisheries ..........................................................3.7-7
3.7.3.2.1
No
3.7.3.3
Environmental Consequences....................................................3.7-7
3.7.3.3.1
Reservoir Sport Fisheries ..........................................................3.7-7
3.7.3.3.2
Colorado River Sport Fisheries .................................................3.7-8
3.8
SPECIAL-STATUS SPECIES ........................................................................3.8-1
3.8.1
Introduction ...............................................................................3.8-1
3.8.2
Methodology..............................................................................3.8-2
3.8.3
Affected Environment ...............................................................3.8-2
3.8.3.1
Lake and Riparian Habitat.........................................................3.8-2
3.8.3.1.1
Lakeside Habitat ........................................................................3.8-2
3.8.3.1.2
Riverside Habitat .......................................................................3.8-5
3.8.3.2
Special-Status Plant Species......................................................3.8-6
3.8.3.2.1
Plant Species Removed from Further Consideration ................3.8-8
3.8.3.2.2
Plant Species Considered Further..............................................3.8-8
3.8.3.3
Special-Status Wildlife Species...............................................3.8-10
3.8.3.3.1
Wildlife Species Removed from Further Consideration .........3.8-12
3.8.3.3.2
Special-Status Wildlife Species Considered Further...............3.8-14
3.8.3.4
Special-Status Fish Species .....................................................3.8-18
3.8.4
Environmental Consequences..................................................3.8-22

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3.8.4.1
3.8.4.1.1
3.8.4.1.2
3.8.4.2
3.8.4.2.1
3.8.4.2.2
3.8.4.3
3.8.4.3.1
3.8.4.3.2

Effects on Special-Status Plant Species ..................................3.8-22
Baseline Conditions.................................................................3.8-22
Effects of the Alternatives .......................................................3.8-23
Effects on Special-Status Wildlife Species .............................3.8-24
Baseline Conditions.................................................................3.8-24
Effects of the Alternatives .......................................................3.8-25
Effects on Special-Status Fish Species....................................3.8-25
Baseline Conditions.................................................................3.8-26
Effects of the Alternatives .......................................................3.8-27

3.9
3.9.1
3.9.2

RECREATION ................................................................................................3.9-1
Introduction ...............................................................................3.9-1
Reservoir Marinas, Boat Launching and
Shoreline Access .......................................................................3.9-1
3.9.2.1
Methodology..............................................................................3.9-1
3.9.2.2
Affected Environment ...............................................................3.9-2
3.9.2.2.1
Lake Powell Recreation Resources ...........................................3.9-2
3.9.2.2.2
Shoreline Public Use Facilities..................................................3.9-5
3.9.2.2.2.1
Threshold Elevations .................................................................3.9-8
3.9.2.2.3
Lake Mead Recreation Resources .............................................3.9-9
ior
3.9.2.2.4
Shoreline Public Use Facilities at Lake tMead...........................3.9-9
In er 17
0
f the
3.9.2.2.4.1
Threshold Elevations ...............................................................3.9-13
pt. o er 29, 2
e
3.9.2.3
Environmental n v. D
mb
o Consequences..................................................3.9-13
ati.............................................................................3.9-14
Nove
3.9.2.3.1
Lakejo N
Powell
n
ava chived o
NBaselinerConditions.................................................................3.9-20
3.9.2.3.1.1 in
a
cited
3.9.2.3.1.2 16Basin States Alternative ..........................................................3.9-20
864,
1 - Flood Control Alternative........................................................3.9-21
3.9.2.3.1.3 4
No.
3.9.2.3.1.4
Six States Alternative ..............................................................3.9-21
3.9.2.3.1.5
California Alternative ..............................................................3.9-21
3.9.2.3.1.6
Shortage Protection Alternative...............................................3.9-22
3.9.2.3.2
Lake Mead ...............................................................................3.9-22
3.9.2.3.2.1
Baseline Conditions.................................................................3.9-25
3.9.2.3.2.2
Basin States Alternative ..........................................................3.9-25
3.9.2.3.2.3
Flood Control Alternative........................................................3.9-25
3.9.2.3.2.4
Six States Alternative ..............................................................3.9-25
3.9.2.3.2.5
California Alternative ..............................................................3.9-25
3.9.2.3.2.6
Shortage Protection Alternative...............................................3.9-26
3.9.3
Reservoir Boating/Navigation .................................................3.9-26
3.9.3.1
Methodology............................................................................3.9-26
3.9.3.2
Affected Environment .............................................................3.9-27
3.9.3.2.1
Lake Powell Boating Navigation and Safety...........................3.9-27
3.9.3.2.1.1
Lake Powell Safe Boating Capacity ........................................3.9-28
3.9.3.2.2
Lake Mead Boating Navigation and Safety.............................3.9-29
3.9.3.2.3
Lake Mead Safe Boating Capacity ..........................................3.9-30
3.9.3.3
Environmental Consequences..................................................3.9-31

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3.9.3.3.1
3.9.3.3.1.1
3.9.3.3.1.2
3.9.3.3.1.3
3.9.3.3.1.4
3.9.3.3.1.5
3.9.3.3.1.6
3.9.3.3.2
3.9.3.3.2.1
3.9.3.3.2.2
3.9.3.3.2.3
3.9.3.3.2.4
3.9.3.3.2.5
3.9.3.3.2.6
3.9.4
3.9.5
3.9.5.1
3.9.5.2
3.9.5.2.1
3.9.5.2.2
3.9.5.2.3
3.9.5.3
3.9.5.3.1

Lake Powell .............................................................................3.9-32
Baseline Conditions.................................................................3.9-34
Basin States Alternative ..........................................................3.9-34
Flood Control Alternative........................................................3.9-34
Six States Alternative ..............................................................3.9-35
California Alternative ..............................................................3.9-35
Shortage Protection Alternative...............................................3.9-35
Lake Mead ...............................................................................3.9-35
Baseline Conditions.................................................................3.9-37
Basin States Alternative ..........................................................3.9-37
Flood Control Alternative........................................................3.9-38
Six States Alternative ..............................................................3.9-38
California Alternative ..............................................................3.9-38
Shortage Protection Alternative...............................................3.9-38
River and Whitewater Boating ................................................3.9-39
Sport Fishing ...........................................................................3.9-39
Methodology............................................................................3.9-40
Affected Environment .............................................................3.9-40
Sport Fishing in Lake Powell ..................................................3.9-40
ior
Sport Fishing in Lake Mead ....................................................3.9-41
Inter 17
the
Sport Fishing in Lake Mohavef................................................3.9-43
0
pt. o er 29, 2
e
Environmental Consequences..................................................3.9-44
v. D
mb
Sport Fishingon Lake Powell, Lake Mead and
ati in on Nove
oN
avaj rchived
NLake Mohave ...........................................................................3.9-44
in
a
3.9.6
cited 16Recreational Facilities Operational Costs ...............................3.9-45
864,
3.9.6.1
14- Methodology............................................................................3.9-45
No.
3.9.6.2
Affected Environment .............................................................3.9-45
3.9.6.2.1
Lake Powell .............................................................................3.9-45
3.9.6.2.2
Lake Mead ...............................................................................3.9-47
3.9.6.3
Environmental Consequences..................................................3.9-48
3.9.6.3.1
Lake Powell .............................................................................3.9-48
3.9.6.3.2
Lake Mead ...............................................................................3.9-48

3.10
ENERGY RESOURCES ...............................................................................3.10-1
3.10.1
Introduction .............................................................................3.10-1
3.10.2
Hydropower .............................................................................3.10-1
3.10.2.1
Methodology............................................................................3.10-1
3.10.2.2
Affected Environment .............................................................3.10-2
3.10.2.2.1
Factors of Power Production ...................................................3.10-2
3.10.2.2.2
Power Marketing and Customers ............................................3.10-3
3.10.2.3
Environmental Consequences..................................................3.10-4
3.10.2.3.1
Baseline Conditions.................................................................3.10-5
3.10.2.3.1.1
Glen Canyon Dam ...................................................................3.10-5
3.10.2.3.1.2
Hoover Dam ............................................................................3.10-5
3.10.2.3.1.3
Combined Capacity and Energy Reduction Under

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Baseline Conditions.................................................................3.10-8
Basin States Alternative ..........................................................3.10-8
Glen Canyon Dam ...................................................................3.10-8
Hoover Dam ............................................................................3.10-8
Flood Control Alternative........................................................3.10-8
Glen Canyon Dam ...................................................................3.10-8
Hoover Dam ............................................................................3.10-9
Six States Alternative ..............................................................3.10-9
Glen Canyon Dam ...................................................................3.10-9
Hoover Dam ............................................................................3.10-9
California Alternative ............................................................3.10-10
Glen Canyon Dam .................................................................3.10-10
Hoover Dam ..........................................................................3.10-10
Shortage Protection Alternative.............................................3.10-10
Glen Canyon Dam .................................................................3.10-10
Hoover Dam ..........................................................................3.10-11
Comparison of Alternatives...................................................3.10-11
Southern Nevada Water System Lake Mead Intake
Energy Requirements ............................................................3.10-13
ior
3.10.3.1
Methodology..........................................................................3.10-13
Inter 17
3.10.3.2
Affected Environment ...........................................................3.10-13
0
f the
pt. o er 29, 2
e
3.10.3.3
Environmental Consequences................................................3.10-13
v. D
mb
3.10.3.3.1
Baseline Conditions and ove
ation on N Alternatives....................................3.10-14
oN
3.10.4
avaj Energy Requirements at Lake Powell ........................3.10-14
NIntake archived
3.10.4.1 cited in Methodology..........................................................................3.10-14
864,
16Affected Environment ...........................................................3.10-15
3.10.4.2 . 14o
3.10.4.3N
Environmental Consequences................................................3.10-15
3.10.2.3.2
3.10.2.3.2.1
3.10.2.3.2.2
3.10.2.3.3
3.10.2.3.3.1
3.10.2.3.3.2
3.10.2.3.4
3.10.2.3.4.1
3.10.2.3.4.2
3.10.2.3.5
3.10.2.3.5.1
3.10.2.3.5.2
3.10.2.3.6
3.10.2.3.6.1
3.10.2.3.6.2
3.10.2.4
3.10.3

3.11
AIR QUALITY ..............................................................................................3.11-1
3.11.1
Introduction .............................................................................3.11-1
3.11.2
Fugitive Dust from Exposed Shoreline ...................................3.11-1
3.11.2.1
Methodology............................................................................3.11-1
3.11.2.2
Affected Environment .............................................................3.11-2
3.11.2.3
Environmental Consequences..................................................3.11-3
3.12
VISUAL RESOURCES.................................................................................3.12-1
3.12.1
Introduction .............................................................................3.12-1
3.12.2
Methodology............................................................................3.12-1
3.12.3
Affected Environment .............................................................3.12-1
3.12.3.1
Lake Powell .............................................................................3.12-2
3.12.3.1.1
Landscape Character................................................................3.12-2
3.12.3.1.2
Sensitive Viewing Locations ...................................................3.12-2
3.12.3.2
Lake Mead ...............................................................................3.12-3
3.12.3.2.1
Landscape Character................................................................3.12-3
3.12.3.2.2
Sensitive Viewing Locations ...................................................3.12-3
3.12.4
Environmental Consequences..................................................3.12-4

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3.12.4.1
3.12.4.1.1
3.12.4.1.2
3.12.4.2
3.12.4.2.1
3.12.4.2.2
3.12.4.3
3.12.4.3.1
3.12.4.3.2
3.12.4.4
3.12.4.4.1
3.12.4.4.2
3.12.4.5
3.12.4.5.1
3.12.4.5.2
3.12.4.6
3.12.4.6.1
3.12.4.6.2
3.13
3.13.1
3.13.2
3.13.3
3.13.4

Baseline Conditions.................................................................3.12-4
Lake Powell .............................................................................3.12-4
Lake Mead ...............................................................................3.12-5
Basin States Alternative ..........................................................3.12-6
Lake Powell .............................................................................3.12-6
Lake Mead ...............................................................................3.12-6
Flood Control Alternative........................................................3.12-6
Lake Powell .............................................................................3.12-6
Lake Mead ...............................................................................3.12-6
Six States Alternative ..............................................................3.12-7
Lake Powell .............................................................................3.12-7
Lake Mead ...............................................................................3.12-7
California Alternative ..............................................................3.12-7
Lake Powell .............................................................................3.12-7
Lake Mead ...............................................................................3.12-8
Shortage Protection Alternative...............................................3.12-8
Lake Powell .............................................................................3.12-8
Lake Mead ...............................................................................3.12-8

CULTURAL RESOURCES ..........................................................................3.13-1
ior
Introduction .............................................................................3.13-1
Inter 17
0
f the
Approach to Analysis ..............................................................3.13-1
pt. o er 29, 2
e
v. D
Affected Environment .............................................................3.13-2
mb
ation on Nove
Environmental Consequences..................................................3.13-3
ajo N
d

Nav

hive

n
3.14
INDIAN iTRUST4, arc ............................................................................3.14-1
ASSETS
cited 16Introduction .............................................................................3.14-1
86
3.14.1
14No.
3.14.2
Ten Tribes Partnership ............................................................3.14-1
3.14.2.1
Northern Ute Indian Tribe – Uintah and Ouray
Reservation ..............................................................................3.14-2
3.14.2.2
Jicarilla Apache Indian Reservation ........................................3.14-3
3.14.2.3
Navajo Indian Reservation ......................................................3.14-4
3.14.2.4
Southern Ute Reservation........................................................3.14-5
3.14.2.5
Ute Mountain Ute Indian Reservation.....................................3.14-5
3.14.2.6
Fort Mojave Indian Reservation ..............................................3.14-6
3.14.2.7
Chemehuevi Indian Reservation..............................................3.14-7
3.14.2.8
Colorado River Indian Reservation .........................................3.14-7
3.14.2.9
Quechan Indian Reservation (Fort Yuma)...............................3.14-8
3.14.2.10
Cocopah Indian Tribe ..............................................................3.14-9
3.14.2.11
Environmental Consequences................................................3.14-10
3.14.2.11.1
Upper Basin Mainstem Tribes...............................................3.14-10
3.14.2.11.2
Lower Basin Mainstem Tribes ..............................................3.14-11
3.14.3
Tribes served by Central Arizona Project..............................3.14-11
3.14.3.1
Water Rights Setting..............................................................3.14-11
3.14.3.1.1
CAP Priority Scheme ............................................................3.14-11
3.14.3.1.2
Examples of Reductions of CAP Water Deliveries...............3.14-14
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TABLE OF CONTENTS

3.14.3.2
3.14.3.2.1
3.14.3.2.2
3.15

Environmental Consequences................................................3.14-18
Impacts Resulting from Baseline Conditions
and Alternatives.....................................................................3.14-18
Summary of Impacts..............................................................3.14-20

ENVIRONMENTAL JUSTICE ....................................................................3.15-1

3.16
TRANSBOUNDARY IMPACTS..................................................................3.16-1
3.16.1
Introduction .............................................................................3.16-1
3.16.2
Methodology............................................................................3.16-1
3.16.3
Consultation With Mexico ......................................................3.16-2
3.16.4
Affected Environment .............................................................3.16-4
3.16.4.1
Historical Colorado River Between the Southerly
International Boundary and the Gulf of California .................3.16-4
3.16.4.2
Present Status of the Colorado River Between the NIB
and the Gulf of California........................................................3.16-5
3.16.5
Excess Flows to Mexico........................................................3.16-10
3.16.5.1
Baseline Conditions...............................................................3.16-10
3.16.5.2
Comparison of Surplus Alternatives to
Baseline Conditions...............................................................3.16-15
3.16.5.3
Potential Transboundary Effects of Reduced r
terio Flood
Flow Frequency .....................................................................3.16-22
he In 2017
of t
9,
3.16.5.3.1
General Effects of . Dept.
Flood Flows.............................................3.16-22
ber 2
v
3.16.5.3.2
Effects of ation Excessvem
N Reducedon No Flows..........................................3.16-23
o
3.16.5.4
Summary Ofved
avaj
i Potential Effects To Special-Status Status
in Nand4, archIn Mexico ...........................................................3.16-23
Habitat
d
cite 16Potential Effects to Habitat in Mexico ..................................3.16-23
86
3.16.5.5
. 14- Potential Effects to Special Status-Species in Mexico .........3.16-24
No
3.16.5.5.1
3.16.5.5.2
Desert pupfish........................................................................3.16-24
3.16.5.5.3
Vaquita ..................................................................................3.16-26
3.16.5.5.4
Totoaba ..................................................................................3.16-28
3.16.5.5.5
Southwestern Willow Flycatcher...........................................3.16-30
3.16.5.5.6
Yuma Clapper Rail ................................................................3.16-33
3.16.5.5.7
Yellow-billed Cuckoo ...........................................................3.16-36
3.16.5.5.8
California Black Rail .............................................................3.16-37
3.16.5.5.9
Elf Owl ..................................................................................3.16-38
3.16.5.5.10
Bell’s Vireo ...........................................................................3.16-39
3.16.5.5.11
Clark’s Grebe.........................................................................3.16-40
3.17
3.17.1
3.17.2
3.17.3
3.17.4
3.17.5
3.17.6

SUMMARY OF ENVIRONMENTAL COMMITMENTS ..........................3.17-1
Water Quality ..........................................................................3.17-1
Riverflow Issues ......................................................................3.17-2
Aquatic Resources ...................................................................3.17-2
Special-Status Species .............................................................3.17-2
Recreation................................................................................3.17-2
Cultural Resources...................................................................3.17-2

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

3.17.7
4

Transboundary Impacts ...........................................................3.17-3

OTHER NEPA CONSIDERATIONS...............................................................................4-1
4.1
4.2

CUMULATIVE IMPACTS................................................................................4-1

4.3

RELATIONSHIP BETWEEN SHORT-TERM USES OF THE
ENVIRONMENT AND LONG-TERM PRODUCTIVITY...............................4-2

4.4
5

INTRODUCTION ..............................................................................................4-1

IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF
RESOURCES .....................................................................................................4-3

CONSULTATION AND COORDINATION...................................................................5-1
5.1

INTRODUCTION ..............................................................................................5-1

5.2
5.2.1
5.2.2

GENERAL PUBLIC INVOLVEMENT ACTIVITIES......................................5-1
Project Scoping.............................................................................5-1
Public Review Of DEIS................................................................5-2

5.3
5.3.1
5.3.2

FEDERAL AGENCY COORDINATION .........................................................5-2
National Park Service ...................................................................5-2
United States Section of the International rior
te Boundary and
he In 2017
Water Commission .......................................................................5-3
. of t r 2 ........................................5-3
e Indian Affairs 9,
United States Bureau of pt
be
v. D
United Stateson and NovemService Including
ati Fish on Wildlife
oN
avaj rch ved
NEndangered iSpecies Act Compliance...........................................5-3
in
a
cited 16National Marine Fisheries Service ...............................................5-4
864, Historic Preservation Act Compliance ..........................5-5
14- National

5.3.3
5.3.4
5.3.5
5.3.6

No.

5.4

TRIBAL CONSULTATION ..............................................................................5-6

5.5

STATE AND LOCAL WATER AND POWER AGENCIES
COORDINATION ..............................................................................................5-6

5.6

NON-GOVERNMENTAL ORGANIZATIONS COORDINATION ................5-7

5.7

MEXICO CONSULTATION .............................................................................5-7

5.8

SUMMARY OF COORDINATION CONTACTS ............................................5-8

5.9

FEDERAL REGISTER NOTICES...................................................................5-12

Glossary

GL-1

Index

IND-1

References Cited

REF-1

List of Preparers

LOP-1

Document Distribution

DIST-1

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

List of Tables
Table 1-1

Documents Included in the Law of the River............................................1-11

Table 1-2

Colorado River Storage Facilities and Major Diversion Dams from
Lake Powell to Morelos Dam....................................................................1-19

Table 2-1

Baseline Potential Surplus Water Supply..................................................2-10

Table 2-2

Basin States Alternative Potential Surplus Water Supply.........................2-13

Table 2-3

Flood Control Potential Alternative Surplus Water Supply ......................2-15

Table 2-4

Six States Alternative Potential Surplus Water Supply.............................2-18

Table 2-5

California Alternative Potential Surplus Water Supply ............................2-20

Table 2-6

Shortage Protection Alternative Potential Surplus Water Supply.............2-22

Table 2-7

Summary of Potential Effects of Implementing Interim Surplus
Criteria.......................................................................................................2-24

Table 3.3-1

Glen Canyon Dam Release Restrictions...................................................3.3-3

Table 3.3-2

Minimum Required Colorado River System Storage or
Space ....................3.3-4

Table 3.3-3
Table 3.3-4

Table 3.3-5

teri
,2
er 29

In
Minimum Flood Control Releases at Hoover Dam ..................................3.3-5
017
f the
pt. o

Lake Powell End-of-July Water e emb Comparison of Surplus
v. D Elevations;
ation Condition; 90th, 50th and 10th
Alternatives and Baseline on Nov
ajo N
Percentileav
....................................................................................3.3-25
N Valuesrchived
in

a
ed
citLake Powell 4,
1686 End-of-July Water Elevations; Comparison of Surplus
. 14NoAlternatives and Baseline Conditions; Percentage of Values

Greater than or Equal to Elevation 3695 Feet ........................................3.3-27
Table 3.3-6

Lake Powell End-of-July Water Elevations; Comparison of Surplus
Alternatives and Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 3612 Feet ........................................3.3-27

Table 3.3-7

Lake Mead End-of-December Water Elevations Comparison of
Surplus Alternatives and Baseline Conditions; 90th, 50th and
10th Percentile Values .............................................................................3.3-37

Table 3.3-8

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives and Baseline Conditions; Percentage of
Values Greater than or Equal to Elevation 1200 Feet ............................3.3-41

Table 3.3-9

Lake Mead End-of-December Water Elevations Comparison of
Surplus Alternatives and Baseline Conditions Percentage of
Values Greater than or Equal to Elevation 1083 Feet ............................3.3-41

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Table 3.3-10

Table 3.3-11

Lake Mead End-of-December Water Elevations;Comparison of
Surplus Alternatives and Baseline Conditions; Percentage of
Values Greater than or Equal to Elevation 1050 Feet ............................3.3-41
Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives and Baseline Conditions; Percentage of
Values Greater than or Equal to Elevation 1000 Feet ............................3.3-42

Table 3.3-12

Colorado River Flow Locations Identified for Evaluation ....................3.3-42

Table 3.3-13

Comparison of Mean Monthly Flow (cfs) – Baseline Conditions
and Surplus Alternatives; Colorado River Downstream of Havasu
NWR (River Mile = 242.3); 70th Percentile Values for Year 2016........3.3-48

Table 3.3-14

Comparison of Mean Monthly Flow (cfs) – Baseline Conditions and
Surplus Alternatives; Colorado River Upstream of CRIR Diversion
(River Mile = 180.8); 70th Percentile Values for Year 2016 ..................3.3-58

Table 3.3-15

Comparison of Mean Monthly Flow (cfs) – Baseline Conditions
and Surplus Alternatives; Colorado River Downstream of Palo Verde
Diversion Dam (River Mile = 133.8); 70th Percentile Values for
ior
Year 2016 ...............................................................................................3.3-64
Inter

Table 3.3-16

Table 3.4-1

f the

017

9, 2
Comparison of Mean Monthly Flow.Data – Baseline Conditions
pt o
. De Riverber 2
and Surplus Alternatives; Colorado vem Downstream of Morelos
nv
o
Natio d onPercentile Values (cfs)
Dam (River Mile = 23.1); 90th N
vajo hive
Na
for Year 2016..........................................................................................3.3-75
d in
, arc

cite 16864
Summary of Arizona Modeled Annual Depletions; Comparison
. 14Noof Surplus Alternatives to Baseline Conditions......................................3.4-24

Table 3.4-2

Summary of California Modeled Annual Depletions; Comparison
of Surplus Alternatives to Baseline Conditions......................................3.4-33

Table 3.4-3

Summary of Nevada Modeled Annual Depletions; Comparison
of Surplus Alternatives to Baseline Conditions......................................3.4-41

Table 3.4-4

Summary of Mexico Modeled Annual Depletions; Comparison
of Surplus Alternatives to Baseline Conditions......................................3.4-47

Table 3.5-1

Estimated Colorado River Salinity in 2016............................................3.5-10

Table 3.5-2

Estimated Colorado River Salinity in 2050............................................3.5-10

Table 3.5-3

Morphometric Characteristics of Lake Mead.........................................3.5-12

Table 3.5-4

Chemical Characteristics of Colorado River ..........................................3.5-16

Table 3.5-5

Hydraulic Inputs for Lake Mead ............................................................3.5-18

Table 3.5-6

Modeled Characteristics of Lake Mead Under Baseline and
Alternative Conditions............................................................................3.5-24

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TABLE OF CONTENTS

Table 3.5-7

Modeled Comparisons of Alternatives to Baseline Conditions .............3.5-24

Table 3.6-1

Probabilities of BHBF Releases from Glen Canyon Dam .......................3.6-3

Table 3.6-2

Probability of Minimum Glen Canyon Dam Releases
(Annual Releases of 8.23 maf) .................................................................3.6-8

Table 3.6-3

Development in Flood Plains Between Hoover Dam and
SIB, 1979 Data .......................................................................................3.6-10

Table 3.6-4

Discharge Probabilities from Hoover, Davis and Parker Dams .............3.6-12

Table 3.6-5

Estimated Flood Damages Between Hoover Dam and the SIB
(1979 level of development and 2000 price level1)................................3.6-12

Table 3.7-1

Fish Species Present in the Project Area ..................................................3.7-3

Table 3.8-1

Special-Status Plant Species Potentially Occurring Within the
Area of Analysis .......................................................................................3.8-7

Table 3.8-2

Special-Status Wildlife Species Potentially Occurring Within the
Area of Analysis .....................................................................................3.8-11

Table 3.8-3

Special-Status Fish Species Potentially Occurring Within the
r
Area of Analysis .....................................................................................3.8-18
terio

Table 3.9-1
Table 3.9-2

he In
r
mbe

7

01
Glen Canyon National Recreationpt. ofVisitation,..................................3.9-3
Area t
29 2
. De
n
ed o

Lake Powell Shorelineon v Useove
ati Public N Facilities............................................3.9-6

jo N
ited 6864, a
Table 3.9-4 c Probabilities of Lake Powell Elevation Exceeding 3677 feet
-1
. July
oin14 .....................................................................................................3.9-17
N
Table 3.9-3

Laken Nava rcPublic Use Facilities ...............................................3.9-10
i Mead Marina hiv

Table 3.9-5

Probabilities of Lake Powell Elevation Exceeding 3612 feet
in July .....................................................................................................3.9-18

Table 3.9-6

Comparison of Lake Mead Elevation Exceedance Probabilities
for Elevation 1183 Feet ..........................................................................3.9-22

Table 3.9-7

Lake Powell Safe Boating Capacity at Water Surface Elevations .........3.9-29

Table 3.9-8

Lake Mead Safe Boating Capacity at Water Surface Elevations ...........3.9-31

Table 3.9-9

Probabilities of Lake Powell Elevation Exceeding 3626 feet
in July .....................................................................................................3.9-34

Table 3.9-10

Probabilities of Lake Mead End-of-December Elevation Exceeding
1170 feet .................................................................................................3.9-37

Table 3.9-11

Nevada Division of Wildlife Annual Angler Questionnaire
Results for Lake Mead............................................................................3.9-42

Table 3.9-12

Lake Mohave Developed Recreation Facilities......................................3.9-43

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Table 3.9-13

Costs Associated with Adjustments to Lake Powell Recreation
Facilities .................................................................................................3.9-46

Table 3.9-14

Costs Incurred to Recreational Facilities from Lake Mead Pool
Fluctuations (Year 2000 Price Level).....................................................3.9-47
Costs Associated with Potential Relocation of Lake Powell
Recreational Facilities Under Alternatives; Compared to Baseline
Conditions (Year 2000 Price Level).......................................................3.9-48

Table 3.9-15

Table 3.9-16

Costs Associated with Potential Relocation of Lake Mead
Recreational Facilities Under Alternatives Compared to
Baseline Conditions................................................................................3.9-49

Table 3.10-1

Hydropower Capacity and Energy – Comparison of Alternatives
to Baseline Conditions; (Difference between baseline conditions
and each alternative2) ..........................................................................3.10-12

Table 3.10-2

Southern Nevada Water System Lake Mead Intake Energy
Requirements Average Annual Power Cost – Comparison of
Alternatives to Baseline Conditions; (Differences between baseline
conditions and each alternative) ...........................................................3.10-14

Table 3.10-3

r

io
Intake Energy Requirements at Lake Powell Average Annual
Inter 17
heBaseline0Conditions
Power Cost – Comparison of Alternatives to
of t
9 2
ept. and reach ,alternative) ...........3.10-16
(Difference between baseline D
. conditions be 2
v
m

n
e
Natio d on Nov
Table 3.11-1
Median Lake Mead Surface Elevation
ajo
av
ive
SurfaceN
d in Area4and rch
, a Exposed Shoreline Area Under Baseline
e
citConditions6 Alternative Projections..................................................3.11-5
168 and
. 14o
Table 3.11-2 N Median Lake Powell Surface Elevation, Surface Area and Exposed

Shoreline Area Under Baseline Conditions and Alternative
Projections ..............................................................................................3.11-6
Table 3.14-1

Central Arizona Project Indian Water Allocations...............................3.14-13

Table 3.14-2

Traditional Reclamation Priorities for Central Arizona
Project Water ........................................................................................3.14-15

Table 3.14-3

Reductions in Indian CAP Water Supplies During Times of
Shortage on Colorado River Likely Future Without
GRIC Settlement ..................................................................................3.14-16

Table 3.14-4

Reductions in Indian CAP Water Supplies During Times of
Shortage on Colorado River (Likely Future with GRIC
Settlement)............................................................................................3.14-17

Table 3.16-1

Frequency Occurrence of Excess Flows Below Mexico Diversion at
Morelos Dam Comparison of Surplus Alternatives to Baseline
Conditions.............................................................................................3.16-15

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Table 3.16-2

Excess Flows Below Mexico Diversion at Morelos Dam;
Comparison of Surplus Alternatives to Baseline Conditions;
75th Percentile Values for Selected Years (kaf)....................................3.16-20

Table 3.16-3

Excess Flows Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions;
90th Percentile Values for Selected Years (kaf)....................................3.16-21
Yellow-billed Cuckoos Survey Results................................................3.16-37

Table 3.16-4
Table 5-1

Participants with Reclamation Regarding the Interim Surplus
Criteria Environmental Impact Statement Process......................................5-9

Table 5-2

Federal Register Notices Regarding Interim Surplus Criteria ..................5-12

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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List of Figures
Figure 1-1

Locations of Lee Ferry and Lees Ferry .......................................................1-6

Figure 1-2

Schematic of Colorado River Releases and Diversions ............................1-14

Figure 2-1

Baseline Surplus Trigger Elevations ...........................................................2-9

Figure 2-2

Basin States Alternative Surplus Trigger Elevations ................................2-12

Figure 2-3

Flood Control Alternative Surplus Trigger Elevations..............................2-16

Figure 2-4

Six States Alternative Surplus Trigger Elevations ....................................2-17

Figure 2-5

California Alternative Surplus Trigger Elevations....................................2-21

Figure 2-6

Shortage Protection Alternative Trigger Elevations..................................2-23

Figure 3.3-1

Natural Flow at Lees Ferry Stream Gage .................................................3.3-7

Figure 3.3-2

Historic Annual Flow at Lees Ferry Stream Gage ...................................3.3-8

Figure 3.3-3

Lake Powell and Glen Canyon Dam Important Operating
Elevations ...............................................................................................3.3-19

Figure 3.3-4
Figure 3.3-5

Figure 3.3-6

rior
0
29, 2

nte
Historic Lake Powell Water Levels........................................................3.3-20
17
the I
t. of

Lake Powell End-of-July Water ep
. D Elevations er
b Under Baseline
th
th ion v th
vemValues and Representative
Conditions; 90 , 50atand 10 n No
Percentile
N
vajo hived o
Traces .....................................................................................................3.3-21
Na

arc
ed in 86 End-of-July Water Elevations; Comparison of
citLake Powell 4,
16
. 14oSurplus Alternatives to Baseline Conditions; 90th, 50th and 10th
N

Percentile Values ....................................................................................3.3-23

Figure 3.3-7

Lake Powell End-of-July Water Elevations; Comparison of
Surplus Alternatives to Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 3695 Feet ........................................3.3-24

Figure 3.3-8

Lake Powell End-of-July Water Elevations; Comparison of
Surplus Alternatives to Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 3612 Feet ........................................3.3-26

Figure 3.3-9

Histogram of Modeled Lake Powell Annual Releases (Water Years)
2002 to 2016 (85 Traces) .......................................................................3.3-28

Figure 3.3-10

Lake Mead and Hoover Dam Important Operating Elevations..............3.3-30

Figure 3.3-11

Historic Lake Mead Water Levels (Annual Highs and Lows) ...............3.3-32

Figure 3.3-12

Lake Mead End-of-December Water Elevations Under Baseline
Conditions; 90th, 50th and 10th Percentile Values and Representative
Traces .....................................................................................................3.3-33

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Figure 3.3-13

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives and Baseline Conditions; 90th, 50th and 10th
Percentile Values ...................................................................................3.3-35

Figure 3.3-14

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives and Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 1200 Feet ........................................3.3-36

Figure 3.3-15

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives to Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 1083 Feet .......................................3.3-38

Figure 3.3-16

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives to Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 1050 Feet ........................................3.3-39

Figure 3.3-17

Lake Mead End-of-December Water Elevations; Comparison of
Surplus Alternatives to Baseline Conditions; Percentage of Values
Greater than or Equal to Elevation 1000 Feet ........................................3.3-40

Figure 3.3-18

Colorado River Downstream of Havasu NWR Annual Flow
Volume (af); Comparison of Surplus Alternatives toior
Baseline
Inter 17
Conditions; (0th, 50th, and 10th Percentile Values ...................................3.3-46
he

Figure 3.3-19

t. of

t

, 20

Colorado River Annual Flow Volume Downstream of Havasu NWR;
Dep mber 29
n v.
Comparison of Surplus Alternativesve Baseline Conditions for
atio on No to
ajo N ................................................................................3.3-49
Modeled Year 2016 hived
Nav

ed in

, arc

Figure 3.3-20a citColorado 864 Seasonal Flows Downstream of Havasu NWR;
16 River
. 14NoComparison of Surplus Alternatives to Baseline Conditions for
Modeled Year 2016 ................................................................................3.3-50
Figure 3.3-20b

Colorado River Seasonal Flows Downstream of Havasu NWR;
Comparison of Surplus Alternatives to Baseline Conditions for
Modeled Year 2016 ................................................................................3.3-51

Figure 3.3-20c

Colorado River Seasonal Flows Downstream of Havasu NWR;
Comparison of Surplus Alternatives to Baseline Conditions for
Modeled Year 2016 ................................................................................3.3-52

Figure 3.3-20d

Colorado River Seasonal Flows Downstream of Havasu NWR;
Comparison of Surplus Alternatives to Baseline Conditions for
Modeled Year 2016 ................................................................................3.3-53

Figure 3.3-21

Colorado River Upstream of CRIR Diversion Annual Flow
Volume (af); Comparison of Surplus Alternatives to Baseline
Conditions; 90th, 50th, and 10th Percentile Values ..................................3.3-55

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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TABLE OF CONTENTS

Figure 3.3-22

Colorado River Annual Flow Volumes Upstream of Colorado River
Indian Reservation; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2006 ........................................................3.3-57

Figure 3.3-23a

Colorado River Seasonal Flows Upstream of Colorado River
Indian Reservation; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ........................................................3.3-59

Figure 3.3-23b

Colorado River Seasonal Flows Upstream of Colorado River
Indian Reservation; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-60

Figure 3.3-23c

Colorado River Seasonal Flows Upstream of Colorado River
Indian Reservation; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-61

Figure 3.3-23d

Colorado River Seasonal Flows Upstream of Colorado River
Indian Reservation;Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-62

Figure 3.3-24

Colorado River Downstream Palo Verde DiversionrDam Annual Flow
ior
Inte Baseline
Volume (af); Comparison of Surplus Alternatives to 017
f the 9, 2
th
th
th
pt. o Values ....................................3.3-65
Conditions; 90 50 and 10 Percentile er 2
De

mb
n v.
atioFlow n Nove Downstream of Palo Verde
Figure 3.3-25
Colorado River Annual
Volumes
ajo N ived o
Irrigation av
N Diversion;hComparison of Surplus Alternatives to
ed in 864, arc
citBaseline Conditions for Modeled Year 2006 .........................................3.3-66
16
. 14Figure 3.3-26aNoColorado River Seasonal Flows Downstream of Palo Verde
Diversion Division; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-67
Figure 3.3-26b

Colorado River Seasonal Flows Downstream of Palo Verde
Diversion Division; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-68

Figure 3.3-26c

Colorado River Seasonal Flows Downstream of Palo Verde
Diversion Division; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-69

Figure 3.3-26d

Colorado River Seasonal Flows Downstream of Palo Verde
Diversion Division; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016........................................................3.3-70

Figure 3.3-27

Colorado River Below Mexico Diversion at Morelos Dam Annual
Flow Volume (af); Comparison of Surplus Alternatives to Baseline
Conditions 90th, 50th and 10th Percentile Values ....................................3.3-73

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Figure 3.3-28

Colorado River Annual Flow Volumes Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2006 ........................................................3.3-74

Figure 3.3-29a

Colorado River Seasonal Flows Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ........................................................3.3-76

Figure 3.3-29b

Colorado River Seasonal Flows Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ........................................................3.3-77

Figure 3.3-29c

Colorado River Seasonal Flows Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ........................................................3.3-78

Figure 3.3-29d

Colorado River Seasonal Flows Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ........................................................3.3-79

Figure 3.4-1

Arizona Projected Colorado River Water Demand Schedules
ior
Inter 17
(Full Surplus, Normal and Shortage Water Supply Conditions) ..............3.4-5
the

Figure 3.4-2
Figure 3.4-3
Figure 3.4-4

t. of

9, 20

California Projected ColoradoDep Water er 2
. River
b Demand Schedules
on Shortage Water
iand v Novem Supply Conditions) ..........3.4-11
(Full Surplus, Normal
Nat
n

vajo

ed o

NevadaNa
ProjectedrColorado River Water Demand Schedules
chiv
ed in 864Normal and Shortage Water Supply Conditions) ............3.4-13
it(Full Surplus, , a
c
-16

. 14
NoUpper Basin Depletion Projections (Based on 1998 Depletion

Schedule) ................................................................................................3.4-15
Figure 3.4-5

Arizona Modeled Annual Depletions Under Baseline Conditions;
90th, 50th and 10th Percentile Values ....................................................3.4-19

Figure 3.4-6

Arizona Modeled Depletions Comparison of Surplus Alternatives to
Baseline Conditions Years 2002 to 2016 ...............................................3.4-21

Figure 3.4-7

Arizona Modeled Depletions Comparison of Surplus Alternatives to
Baseline Conditions Years 2017 to 2050 ...............................................3.4-22

Figure 3.4-8

Arizona Modeled Annual Depletions; Comparison of Surplus
Alternatives to Baseline Conditions; 90th, 50th and 10th
Percentile Values ....................................................................................3.4-25

Figure 3.4-9

California Modeled Annual Depletions Under Baseline Conditions;
90th, 50th and 10th Percentile Values .......................................................3.4-27

Figure 3.4-10

California Modeled Depletions; Comparison of Surplus Alternatives to
Baseline Conditions; Years 2002 to 2016 ..............................................3.4-29

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Figure 3.4-11

California Modeled Depletions; Comparison of Surplus Alternatives
to Baseline Conditions; Years 2017 to 2050 ..........................................3.4-30

Figure 3.4-12

California Modeled Annual Depletions; Comparison of Surplus
Alternatives to Baseline Conditions; 90th, 50th and 10th
Percentile Values ....................................................................................3.4-32

Figure 3.4-13

Nevada Modeled Annual Depletions Under Baseline Conditions;
90th, 50th and 10th Percentile Values ....................................................3.4-35

Figure 3.4-14

Nevada Modeled Depletions; Comparison of Surplus Alternatives to
Baseline Conditions; Years 2002 to 2016 ..............................................3.4-37

Figure 3.4-15

Nevada Modeled Depletions; Comparison of Surplus Alternatives to
Baseline Conditions; Years 2017 to 2050 ..............................................3.4-39

Figure 3.4-16

Nevada Modeled Annual Depletions; Comparison of Surplus
Alternatives to Baseline Conditions; 90th, 50th and 10th
Percentile Values ....................................................................................3.4-40

Figure 3.4-17

Mexico Modeled Annual Depletions Under Baseline Conditions;
90th, 50th and 10th Percentile Values .......................................................3.4-43

Figure 3.4-18
Figure 3.4-19
Figure 3.4-20

ior
Mexico Modeled Depletions; Comparison of Surplus Alternatives to
Inter 17
he
Baseline Conditions; Years 2002 to 2016t..............................................3.4-45
, 20
. of
ept

r 29

.
Mexico Modeled Depletions; D
mbe
ion v Comparison of Surplus Alternatives to
atYears 2017 to ve ..............................................3.4-46
No 2050
Baseline Conditions;
ajo N
d on
Nav

hive

a
ed in Modeled rc
citMexico6864, Annual Depletions; Comparison of Surplus
1
Alternatives to Baseline Conditions; 90th, 50th and 10th
. 14NoPercentile Values ....................................................................................3.4-48

Figure 3.5-1

Historical Monthly Salinity Concentrations Below Glen Canyon
Dam (1940-1995) .....................................................................................3.5-3

Figure 3.5-2

Historical Glen Canyon Dam and Imperial Dam Releases ......................3.5-4

Figure 3.5-3

Historical Salinity Concentrations of Releases from Glen Canyon,
Hoover, and Imperial Dams .....................................................................3.5-5

Figure 3.5-4

Estimated Cost of Damages Associated with Increased Salinity
Concentrations..........................................................................................3.5-8

Figure 3.5-5

Lake Mead End-of-Year Water Elevations; Comparison of Surplus
Alternatives to Baseline Conditions; 50th Percentile Values..................3.5-21

Figure 3.6-1

Lake Powell Releases Probability of Occurrence of BHBF Flows ..........3.6-4

Figure 3.6-2

Lake Powell Releases Probability of Approximately 8.23 maf
Annual Release .........................................................................................3.6-7

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Figure 3.9-1

Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
90th, 50th and 10th Percentile Values ......................................................3.9-15

Figure 3.9-2

Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 3677 Feet msl ....................3.9-16

Figure 3.9-3

Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 3612 Feet msl ....................3.9-19

Figure 3.9-4

Lake Mead End of December Water Elevations
Comparison of Surplus Alternative to Baseline Conditions
90th, 50th and 10th Percentile Values........................................................3.9-23

Figure 3.9-5

Lake Mead End of December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 1183 Feet msl ....................3.9-24

Figure 3.9-6

Lake Powell End of July Water Elevations
ior
Inter 17
Comparison of Surplus Alternatives to Baseline Conditions
0
f the 3626 Feet......................3.9-33
Percentage of Values Greater than or Equal to 29, 2
pt. o
e
r

Figure 3.9-7

v. D

mbe

n
e
Lake Mead End of Decembern NovElevations
Natio d o Water
ajo
Comparison of Surplus Alternatives to Baseline Conditions
Nav archive
d in 64Values Greater than or Equal to 1170 Feet......................3.9-36
e
citPercentage of ,
8
-16

. 14
Figure 3.10-1 NoGlen Canyon Powerplant/Annual Average Energy Production .............3.10-6
Figure 3.10-2

Hoover Powerplant Annual Average Energy Production.......................3.10-7

Figure 3.16-1

Probability of Occurrence of Excess Flows Below Mexico
Diversion at Morelos Dam; Comparison of Surplus Alternatives to
Baseline Conditions..............................................................................3.16-11

Figure 3.16-2

Potential Magnitude of Excess Flows Greater Than 250,000 af
Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions ...............3.16-13

Figure 3.16-3

Potential Magnitude of Excess Flows Greater Than 1,000,000 af
Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions ...............3.16-14

Figure 3.16-4

Potential Magnitude of Excess Flows Below Mexico Diversions at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2016 ......................................................3.16-16

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Figure 3.16- 5

Potential Magnitude of Excess Flows Below Mexico Diversion at
Morelos Dam; Comparison of Surplus Alternatives to Baseline
Conditions for Modeled Year 2050 ......................................................3.16-17

Figure 3.16- 6

Potential Magnitude of Excess Flows To Mexico
90th and 75th Percentile Values ............................................................3.16-19

ior
Inter 17
0
f the
pt. o er 29, 2
e
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ation on Nove
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Nava archived
in
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List of Maps
Map 1-1

Colorado River Drainage Basin...................................................................1-7

Map 1-2

Upper and Lower Basins of the Colorado River .......................................1-10

Map 1-3

Upper and Lower Division States of the Colorado River..........................1-12

Map 1-4

Lower Colorado River Dams.....................................................................1-18

Map 3.2-1

Area of Potential Effect ............................................................................3.2-2

Map 3.3-1

Colorado River Locations Selected for Modeling..................................3.3-44

Map 3.4-1

Colorado River Water Service Areas in the Lower Basin........................3.4-2

Map 3.5-1

Las Vegas Wash and SNWA Lake Mead Intake Facilities at
Saddle Island ..........................................................................................3.5-14

Map 3.9-1

Lake Powell and Associated Shoreline Recreation Facilities ..................3.9-4

Map 3.9-2

Lake Mead and Associated Shoreline Recreation Facilities ..................3.9-11

Map 3.16-1

Colorado River Location Within Mexico...............................................3.16-6

ior
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0
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pt. o er 29, 2
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ation on Nove
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Nava archived
in
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TABLE OF CONTENTS
VOLUME II
Attachment A - Long Range Operating Criteria
Criteria for Coordinated Long-Range Operation of Colorado River Reservoirs
Pursuant to the Colorado River Basin Project Act of September 30, 1968 (p.l. 90-537)
Attachment B - Environmental Guidelines for Transboundary Impacts
Executive Order 12114
Guidance on NEPA Analyses for Transboundary Impacts, Council on Environmental
Quality, 1997
Attachment C - Dams and Reservoirs Along the Lower Colorado River
Attachment D - Glen Canyon Dam Operation Record of Decision
Record of Decision based on Operation of Glen Canyon Dam Final Environmental
Impact Statement, March 1995

ior
Inter 17
Attachment E - Surplus Criteria Proposal by Six Statesthe
,
t. of Criteria 20
Proposal for Interim Lake Mead Reservoirep
Operation er 29 Related to Surplus,
.D
b
nv
em
Normal and Shortage Year Declarations, December 4, 1998
Natio d on Nov
o
avaj rchive
Attachment F - SurplusN
in Criteria Proposal by California
a
cited 16864,
14
Surplus Criteria-for Management of the Colorado River, Exhibit A to a draft document
No. Terms for Quantification of Settlement Among the State of California,
entitled Key
IID, CVWD, and MWD
Attachment G - Surplus Criteria Proposal by Pacific Institute
Letter report dated February 15, 2000
Excerpts from September 8, 2000, letter of comment on the Colorado River Interim
Surplus Criteria DEIS
Attachment H - Lower Division Depletion Schedules
Arizona’s Depletion Schedule
Nevada’s Depletion Schedule
California’s Depletion Schedule with Transfers
California’s Depletion Schedule without Transfers

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Attachment I - Draft Interim Surplus Guidelines
Basin States Alternative Interim Surplus Guidelines
Attachment J - Detailed Modeling Documentation
Attachment K - Upper Division Depletion Schedule
Depletion Schedule for Upper Division States, December 1999
Attachment L - Sensitivity Analysis Comparing Baseline with Transfers to Baseline
Without Transfers
Lake Powell Water Surface Elevations
Lake Mead Water Surface Elevations
Hoover Dam Flood Control Releases
Water Supply
Attachment M - Sensitivity Analysis of Modeled Lake Mead Water Level Protection
Assumptions

ior
Inter 17
0
f the
pt. o er 29, 2
Lake Powell Water Surface Elevations. De
v
mb
ation RiverNove
Attachment N - Comparison ajo N
of Colorado on Flows
Nav archived
in
Comparisond Flows64,
cite of 168 Downstream of the Havasu National Wildlife Refuge Diversion
14Comparison of Flows Upstream of the Colorado River Indian Reservation Diversion
No.
Lake Mead Water Surface Elevations

Comparison of Flows Downstream of the Palo Verde Irrigation District Diversion
Comparison of Flows Below Morelos Dam
Attachment O - Water Supply for Lower Division States
Arizona Water Supply
California Water Supply
Nevada Water Supply

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Attachment P - Energy Analysis Worksheets
Average Lake Mead Elevation and Comparison of SNWA Power Cost
Average Lake Powell Elevation
Glen Canyon Dam Discharge Multiplier and Powerplant Capacity vs. Elevation
Hoover Powerplant Capacity vs. Elevation
Glen Canyon Powerplant Summary of Average Annual Capacity and Energy
Glen Canyon Powerplant Comparison to Baseline Conditions
Hoover Powerplant Summary of Average Annual Capacity and Energy
Hoover Powerplant Comparison to Baseline Conditions
Attachment Q - Ten Tribes Depletion Schedule
Tables of Water Demand Nodes, Water Rights and Depletions for Ten Tribes
Partnership Members used in operational model
Attachment R - Public Scoping Process

ior
Inter 17
e
20
of th
Analysis of Public Scoping Meetings & Dept. Letters 9,
Response er 2
.
emb
on v
atiU.S. FishNovWildlife Service and National
Attachment S - Correspondence with
on and
jo N
Nava archived
Marine Fisheries Services
in
cited 16864,
Memorandum4- May 22, 2000 from Boulder Canyon Operations to Arizona
1 of
No.Services
Ecological
Public Scoping Process

Memorandum of June 5, 2000 from Interior Bureau of Reclamation
Memorandum of August 14, 2000 from Interior to the Bureau of Reclamation
Memorandum of August 31, 2000 from Reclamation to the U.S. Fish and Wildlife
Service
Memorandum of November 29, 2000 from Bureau of Reclamation to the U.S. Fish
and Wildlife Service
Attachment T - Consultation with Mexico
Draft Authority and Assumptions
Letter from Commissioner of Mexico Section of IBWC to United States Section of
IBWC dated May 22, 2000 [in Spanish].
Letter from Commissioner of Mexico Section of IBWC to the United States Section of
IBWC dated May 22, 2000, English translation.

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Letter from Commissioner of Mexico Section of IBWC to United States Section of
IBWC dated October 10, 2000 [in Spanish].
Letter from Commissioner of Mexico Section of IBWC to the United States Section of
IBWC dated October 10, 2000, English translation.

ior
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ation on Nove
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Nava archived
in
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TABLE OF CONTENTS
VOLUME III
INTRODUCTION TO VOLUME III .................................................................................. 1
PART A – PUBLIC HEARINGS AND ORAL COMMENTS ......................................A-1
PART B – COMMENT LETTERS AND RESPONSES................................................ B-1
Individuals
Garcia.......................................................................................................................... B-3
Belles........................................................................................................................... B-4
Forbes Willson ............................................................................................................ B-5
Inskip........................................................................................................................... B-6
Miller........................................................................................................................... B-7
Zarbin.......................................................................................................................... B-9

ior
Inter 17
0
f the
American Water Resources, Inc. .............................................................................. B-11
pt. o er 29, 2
e
v. D
mb
American Water Resources, Inc. .............................................................................. B-12
ation on Nove
jo N
American Water Resources, Inc. .............................................................................. B-14
Nava archive.d..................................................................... B-16
n
Center for Biological Diversity, et,al1
ted i 6 ............................................................................................... B-22
ciof Wildlife864,
Defenders
-1
o. 14
Pacific Institute ......................................................................................................... B-34
N

Organizations

Southwest Rivers ...................................................................................................... B-51
Water User Agencies and Organizations
Central Arizona Water Conservation District (CAWCD) ........................................ B-59
Coachella Valley Water District (CVWD) ............................................................... B-63
Colorado River Energy Distributors Association (CREDA) .................................... B-67
Colorado River Water Conservation District (CRWCD) ......................................... B-69
Cottonwood Creek Consolidated Irrigation Company (CCCIC).............................. B-71
Emery Water Conservancy District (EWCD)........................................................... B-72
Grand Water and Sewer (GW&S) ............................................................................ B-73
Imperial Irrigation District (IID)............................................................................... B-74
Irrigation and Electrical Districts Association of Arizona (I&EDAA) .................... B-77
Metropolitan Water District of Southern California (MWD) ................................... B-89
Mohave County Water Authority (MCWA)............................................................. B-95
Ouray Park Irrigation Company (OPIC)................................................................... B-98

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Water User Agencies and Organizations (Continued)
Salt River Project (SRP) ........................................................................................... B-99
San Diego County Water Authority (SDCWA)...................................................... B-100
Southern California Edison Company (SCEC)....................................................... B-102
Southern Nevada Water Authority (SNWA) .......................................................... B-104
Uintah Water Conservancy District (UWCD) ........................................................ B-106
Union Park Water Authority (UPWA) ................................................................... B-109
Upper Colorado River Commission (UCRC) ......................................................... B-116
Local Agencies
City of Phoenix, Office of the City Manager.......................................................... B-119
Grand County Council (Utah)................................................................................. B-122
State Agencies
Arizona Power Authority (APA) ............................................................................ B-123
Arizona Power Authority (APA) ............................................................................ B-128
ior
Arizona Department of Water Resources (ADWR) ............................................... B-130
Inter 17
Arizona Game and Fish Department (AG&FD)..................................................... B-136
0
f the
pt. o er 29, 2
Colorado River Board of California (CRBC)e
......................................................... B-141
v. D v mb
California Regional Water Quality on
ati Control Boarde
N
n No (CRWQCB) ............................ B-142
Colorado Departmentavajo hived o (CDNR) ............................................ B-144
of Natural Resources
c
in N
New Mexico Interstate 64, ar Commission (NMISC) .......................................... B-146
ited 68 Stream
c
Colorado River 4-1
1 Commission of Nevada (CRCN) .................................................. B-148
No. Commission (Nevada State Historic Preservation
Colorado River
Office-NSHPO).................................................................................................... B-151
New Mexico Environmental Department (NMED)................................................ B-154
Utah Department of Natural Resources, Division of Water Resources
(UDNR, DWR) .................................................................................................... B-155
Office of Federal Land Policy (State of Wyoming) (WOFLP) .............................. B-157
Tribes
Agua Caliente Band of Cahuilla Indians ................................................................ B-165
Hualapai Nation ...................................................................................................... B-167
Navajo Nation Department of Justice (excludes attachments) ............................... B-187
Navajo Tribal Utility Authority .............................................................................. B-191
Ute Mountain Ute Tribe ......................................................................................... B-193
Ten Tribes Partnership............................................................................................ B-194

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Federal Agencies
Bureau of Indian Affairs (BIA)............................................................................... B-221
Bureau of Indian Affairs, Navajo Region ............................................................... B-223
Environmental Protection Agency (EPA)............................................................... B-225
U.S. Fish and Wildlife ............................................................................................ B-238
International Boundary and Water Commission, United States Section
(IBWC, U.S. Section) .......................................................................................... B-278
National Park Service (NPS) .................................................................................. B-281
Western Area Power Administration (WAPA)....................................................... B-286
Western Area Power Administration (WAPA)....................................................... B-287
Western Area Power Administration (WAPA)....................................................... B-289
Mexican Agencies/Organizations
Autonomous University of Baja California (AUBC) ............................................. B-291
International Boundary and Water Commission, Mexican Section
(IBWC, Mexican) ................................................................................................ B-294
Mexicali Business Coordinating Council (MBCC) ................................................ B-296
ior
Mexicali Economic Development Council (MEDC).............................................. B-298
Inter 17
e
National Water Commission (NWC)...................................................................... B-300
of th
, 20

9
pt.
. De ember 2
nv
Additional Tribe
atio
Nov
ajo N ived on
Nav
d in 64, arch
Kaibab Band of Paiute Indians ............................................................................... B-303
cite 168
14No.
Oral Comments
Noble....................................................................................................................... B-305

1

This letter was submitted by the following organizations:
Defenders of Wildlife
Environmental Defense
El Centro de Derecho Ambiental e Integracion Economica del Sur, A.C.
Friends of Arizona Rivers
Glen Canyon Action Network
Glen Canyon Institute
Pacific Institute for Studies in Development, Environment and Security
Sierra Club
Fred Cagle
Jaqueline Garcia-Hernandez

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TABLE OF CONTENTS
EXECUTIVE SUMMARY
S.1 INTRODUCTION AND BACKGROUND.........................................................................1
S.1.1

INTRODUCTION ................................................................................................. 1

S.1.2

PROPOSED FEDERAL ACTION ........................................................................ 4

S.1.3
BACKGROUND ................................................................................................... 4
S.1.3.1
Long-Range Operating Criteria ....................................................... 5
S.1.3.2
Annual Operating Plan ....................................................................6
S.1.4

PURPOSE AND NEED FOR ACTION................................................................ 7

S.1.5

RELATIONSHIP TO UNITED STATES–MEXICO WATER TREATY ........... 8

S.1.6
RELATED AND ON-GOING ACTIONS ............................................................ 8
S.1.6.1
California’s Colorado River Water Use Plan .................................. 8
S.1.6.1.1
Imperial Irrigation District/San Diego County Water
Authority Water Transfer ................................................................ 9
or
S.1.6.1.2
All-American and Coachella Canal Lining iProjects ..................... 10
Inter 17
0
f the
S.1.6.2
Glen Canyon Dam Operations.......................................................10
pt. o er 29, 2
e
S.1.6.2.1
Adaptive Management Program.................................................... 11
v. D
mb
ation on Nove
S.1.6.2.2
Beach/Habitat-Building Flows and Beach/HabitatoN
avaj rch Flows........................................................................ 11
NMaintenanceived
in Temperature Control at Glen Canyon Dam................................... 12
a
S.1.6.2.3cited
864,
16Actions Related to the Biological and Conference Opinion
S.1.6.3
14No.
on Lower Colorado River Operations and Maintenance ............... 12
S.1.6.4
Lower Colorado River Multi-Species Conservation Program ...... 13
S.1.6.5
Secretarial Implementation Agreement Related to
California’s Colorado River Water Use Plan ................................13
S.1.6.6
Offstream Storage of Colorado River Water and
Development and Release of Intentionally Created Unused
Apportionment in the Lower Division States ................................ 14
S.2 ALTERNATIVES .............................................................................................................. 14
S.2.1
DEVELOPMENT OF ALTERNATIVES ........................................................... 14
S.2.1.1
Origins of California, Six States and Basin States
Alternatives....................................................................................14
S.2.1.2
Utilization of Proposals from Basin States.................................... 15
S.2.2
DESCRIPTION OF ALTERNATIVES............................................................... 16
S.2.2.1
No Action Alternative and Baseline Conditions ........................... 16
S.2.2.1.1
Approach to Surplus Water Determination ................................... 16
S.2.2.1.2
70R Baseline Surplus Triggers ...................................................... 16
S.2.2.2
Basin States Alternative (Preferred Alternative) ...........................17

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S.2.2.2.1
S.2.2.2.2
S.2.2.3
S.2.2.3.1
S.2.2.3.2
S.2.2.4
S.2.2.4.1
S.2.2.4.2
S.2.2.5
S.2.2.5.1
S.2.2.5.2
S.2.2.6
S.2.2.6.1
S.2.2.6.2

Approach to Surplus Water Determination ................................... 17
Basin States Alternative Surplus Triggers.....................................18
Flood Control Alternative.............................................................. 18
Approach to Surplus Water Determination ................................... 18
Flood Control Alternative Surplus Triggers..................................18
Six States Alternative .................................................................... 18
Approach to Surplus Water Determination ................................... 18
Six States Alternative Surplus Triggers......................................... 19
California Alternative ....................................................................19
Approach to Surplus Water Determination ................................... 19
California Alternative Surplus Triggers ........................................ 19
Shortage Protection Alternative..................................................... 20
Approach to Surplus Water Determination ................................... 20
Shortage Protection Alternative Surplus Triggers......................... 20

S.3 SUMMARY OF ENVIRONMENTAL CONSEQUENCES .............................................20
S.3.1

USE OF MODELING TO IDENTIFY POTENTIAL FUTURE
COLORADO RIVER SYSTEM CONDITIONS ................................................ 20

S.3.2

BASELINE CONDITIONS................................................................................. 20
r

S.3.3
S.3.4

terio
,2
er 29

In
IMPACT DETERMINATION APPROACH ......................................................21
017
f the
pt. o
ve
n No

PERIOD OF ANALYSIS ....................................................................................21
v. De
mb

n
Natio d o ................................................................. 21
S.3.5
POTENTIALLY ajo
v AFFECTED AREA
e
in Na OF archiv ALTERNATIVES TO BASELINE
d
, SURPLUS
S.3.6
COMPARISON 4
cite 1686
CONDITIONS .....................................................................................................22
14No.
S.3.6.1
Effects on Reservoir Surface Elevations and River Flows............ 22
S.3.6.2
S.3.6.3
S.3.6.3.1
S.3.6.3.2
S.3.6.3.3
S.3.6.3.4
S.3.6.3.5
S.3.6.3.6
S.3.6.3.7

Summary of Environmental Impacts............................................. 24
Environmental Commitments........................................................24
Water Quality ................................................................................ 25
Riverflow Issues ............................................................................25
Aquatic Resources .........................................................................25
Special-Status Species ...................................................................26
Recreation...................................................................................... 26
Cultural Resources.........................................................................26
Transboundary Impacts .................................................................26

S.4 OTHER NEPA CONSIDERATIONS................................................................................ 27
S.4.1

CUMULATIVE IMPACTS................................................................................. 27

S.4.2

RELATIONSHIP BETWEEN SHORT-TERM USES OF THE
ENVIRONMENT AND LONG-TERM PRODUCTIVITY................................ 28

S.4.3

IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF
RESOURCES ...................................................................................................... 28

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TABLE OF CONTENTS

S.5 CONSULTATION AND COORDINATION....................................................................29
S.5.1
GENERAL PUBLIC INVOLVEMENT ACTIVITIES....................................... 29
S.5.1.1
Project Scoping.............................................................................. 29
S.5.1.2
Public Review of DEIS ................................................................. 30
S.5.2
FEDERAL AGENCY COORDINATION .......................................................... 31
S.5.2.1
National Park Service .................................................................... 31
S.5.2.2
U.S. Section of the International Boundary and
Water Commission ........................................................................ 31
S.5.2.3
U.S. Bureau of Indian Affairs........................................................ 31
S.5.2.4
U.S. Fish and Wildlife Service Including Endangered
Species Act Compliance ................................................................ 31
S.5.2.5
National Marine Fisheries Service ................................................ 33
S.5.2.6
National Historic Preservation Act Compliance ...........................33
S.5.3

TRIBAL CONSULTATION ...............................................................................34

S.5.4

STATE AND LOCAL WATER AND POWER AGENCIES
COORDINATION ............................................................................................... 34

S.5.5

NON-GOVERNMENTAL ORGANIZATIONS COORDINATION ................. 35

S.5.6
S.5.7
S.5.8

erior
t. of r 29, 20
SUMMARY OF COORDINATION ep
CONTACTS .............................................36
v. D
mbe
ation on Nove
FEDERAL REGISTER NOTICES .......................................................................36
jo N
Nava archived
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cited 16864,
14No.

nt
MEXICO CONSULTATION .............................................................................. 36
17
the I

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ACRONYMS AND ABBREVIATIONS

4.4 Plan

California 4.4 Plan

°C

degrees Celsius

AAC

All-American Canal

CAP

Central Arizona Project

AAQS

ambient air quality standards

CA PLAN

ADEQ

Arizona Department of
Environmental Quality

California’s Colorado River
Water Use Plan

CAWCD

Arizona Department of Water
Resources

Central Arizona Water
Conservation District

CBRFC

Colorado Basin River Forecast
Center

CDFG

Colorado Department of Fish
and Game
Council on Environmental
Quality

ADWR
af

acre-feet

afy

acre-feet per year

AGFD

Arizona Game and Fish
Department

CEQ

ALP

Animas-La Plata Project

CFR

AMP

Glen Canyon Dam Adaptive
Management Program

cfs

AMWG
AOP
APE

erior
t
t. of r 29, 20
Cleanep
Water Federal Water Pollution
D
be
Adaptive Management Work ion v.
Control Act
Act Novem
at
Group
on
jo N
Nava archivedthe Compact Colorado River Compact of
Annuald in
Plan
1992
cite Operating64,
168Effect
4Area . 1
United States Army Corps of
Corps
No of Potential

AWBA

Arizona Water Banking
Authority

BA

cubic Int per second
he feet
17

Engineers

Biological Assessment

Basin States

Code of Federal Regulations

Council

Advisory Council on Historic
Preservation

Colorado River Basin States

Court

United States Supreme Court

BCO

Biological and Conference
Opinion

CRBPA

Colorado River Basin Project
Act of 1968

BCPA

Boulder Canyon Project Act of
1928

CRFWLS

Colorado River Front Work
and Levee System

BHBF

Beach/Habitat-Building Flow

CRIR

Colorado River Indian
Reservation

BIA

Bureau of Indian Affairs

CRIT

Colorado River Indian Tribes

BLM

Bureau of Land Management

CRMWG

BMI

Basic Management, Inc.

Colorado River Management
Work Group

BO

Biological Opinion

CRSP

Colorado River Storage Project

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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ACRONYMS AND ABBREVIATIONS

CRSPA

Colorado River Storage Project
Act of 1956

CRSS

Colorado River Simulation
System

CRSSez

A simplified version of CRSS

CUP

Central Utah Project

CVWD

Coachella Valley Water
District

Decree

The 1964 U. S. Supreme Court
Decree, Arizona v. California

DEIS

Draft Environmental Impact
Statement

DO
DOE

Gulf

Gulf of California

GWh

gigawatt-hour

HAVFISH

Lake Havasu Fishery
Improvement Project

HCP

Habitat Conservation Plan

IBWC

International Boundary and
Water Commission United
States and Mexico

IID

Imperial Irrigation District

Indian

American Indian

Interior

U.S. Department of the Interior

dissolved oxygen

ISM

Indexed Sequential Method

United States Department of
Energy

ITA

Indian Trust Asset

kaf

thousand acre-feet

EA

Environmental Assessment

kV

kilovolt(s)

EIR

Environmental Impact Report

LCRAS

EIS
EPA
ESA
o

F

rior

nt Colorado River
Lowere
17
the I , 20System
Accounting
9

of
ept. ber 2
v. D
m Lower Colorado River MultiLCRMSCP
ation on Nove
N
Species Conservation Program
Environmentalvajo
Protection
ed
in a 4, archiv
Agency N
Lake Mead National
LMNRA
cited 1686
Recreation Area
4Endangered Species Act of
o. 1 as amended
N 1973,
Long-Range Operating Criteria
LROC
Environmental Impact
Statement

degrees Fahrenheit

LVWCAMP

FEMA

maf

million acre-feet

mafy

million acre-feet per year

Mexico

United Mexican States

μg/g

micrograms per gram

μg/l

microgram per liter
milligram per liter

mg/m3

Finding of No Significant
Impact

municipal and industrial

milligrams per cubic meter

Federal Emergency
Management Agency

FONSI

Las Vegas Wash
Comprehensive Adaptive
Management Plan

M&I

Final Environmental Impact
Statement

Las Vegas Wash Coordination
Committee

mg/l

FEIS

LVWCC

Forum

Colorado River Basin Salinity
Control Forum

FWCA

Fish and Wildlife Coordination
Act of 1934

GCNRA

Glen Canyon National
Recreation Area

GRIC

Gila River Indian Community

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ACRONYMS AND ABBREVIATIONS

MOA

Memorandum of Agreement

P.L.

Public Law

MOC

Memorandum of Clarification

PM

particulate matter

MODE

Main Outlet Drain Extension

ppb

parts per billion

MOU

Memorandum of
Understanding

ppm

parts per million

PPR

present perfected rights

mph

miles per hour

PVID

Palo Verde Irrigation District

MSCP

Multi-Species Conservation
Program

Reclamation

United States Bureau of
Reclamation

msl

mean sea level

RM

river mile

MW

megawatts

RMP

Resource Management Plan

MWD

Metropolitan Water District of
Southern California

ROD

Record of Decision

MWh

megawatt-hours

San Carlos

San Carlos Apache Tribe

NAAQS

National Ambient Air Quality
Standards

SCP

Colorado River Basin Salinity
Control Program

NDEP

Nevada Division of
Environmental Protection

SDCWA

NDOW
NEPA
NFWG
NHPA

San Diego County Water
ior
Int r 7
Authority e
e

01
f th
pt. o SaferDrinking Water Act of
29, 2
e
SDWA
Nevada Division of Wildlife
v. D
mbe
ation on Nove 1974
National Environmental Policy
oN
avaj
United States Secretary of the
Namended rchivedSecretary
Act of 1969, as
in
Interior
ited 6864, a
c
Native Fish 1
4- Work Group
1
Section 7 of the Federal
Section 7
No.
National Historic Preservation
Endangered Species Act
Act of 1966

Section 10

Section 10 of the Federal
Endangered Species Act

Northerly International
Boundary

Service

United States Fish and Wildlife
Service

NIIP

Navajo Indian Irrigation
Project

SHPO

State Historic Preservation
Officer

NMFS

National Marine Fisheries
Service

SIB

Southerly International
Boundary

NPS

National Park Service

SLD

Shoreline Development Value

NWR

National Wildlife Refuge

SNWA

O&M

operation and maintenance

Southern Nevada Water
Authority

Pacific
Institute

Pacific Institute for Studies in
Development Environment and
Security

SNWS

Southern Nevada Water
System

NHWZ

New High Water Zone

NIB

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ACRONYMS AND ABBREVIATIONS

SRPMIC

Salt River Pima Maricopa
Indian Community

USGS

United States Geological
Survey

SWP

California State Water Project

USIBWC

TDS

total dissolved solids

United States Section of the
International Boundary and
Water Commission

Treaty

U.S.-Mexico Water Treaty of
1944

Western

Western Area Power
Administration

UIIP

Uintah Indian Irrigation Project

WSCC

Western States Coordinating
Council

2

Umho/cm

micromhos per centimeter
squared

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ation on Nove
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cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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14No.

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1 INTRODUCTION AND BACKGROUND
1.1 INTRODUCTION
The Secretary of the United States Department of the Interior (Secretary), acting
through the United States Bureau of Reclamation (Reclamation), is considering the
adoption of specific interim criteria under which surplus water conditions may be
declared in the lower Colorado River Basin during a 15-year period that would extend
through 2016.
The Secretary is vested with the responsibility of managing the mainstream waters of
the lower Colorado River pursuant to applicable federal law. This responsibility is
carried out consistent with a collection of documents known as the Law of the River,
which includes a combination of federal and state statutes, interstate compacts, court
decisions and decrees, an international treaty, contracts with the Secretary, operating
criteria, regulations and administrative decisions (see Section 1.3.2.1 for a further
discussion of the Law of the River).
The long-term Colorado River system management objectives are terior
n to:

7
he I
. of t r 29, 201
pt
• Minimize flood damages from river flows,
. De
be
ion v Novem
at withnthe 1964 Decree in Arizona v.
• Release water only inajo N
accordance o
Nav archived
California (Decree),
in
cited 16864,
• Protect and enhance the environmental resources of the basin,
14No.
•

Provide reliable delivery of water for beneficial consumptive use,

•

Increase flexibility of water deliveries under a complex allocation system,

•

Encourage efficient use of renewable water supplies,

•

Minimize curtailment to users who depend on such supplies, and

•

Consider power generation needs.

As the agency that is designated to act on the Secretary’s behalf with respect to these
matters, Reclamation is the Lead Federal Agency for the purposes of NEPA compliance
for the development and implementation of the proposed interim surplus criteria. The
National Park Service (NPS) and the United States Section of the International
Boundary and Water Commission (USIBWC) are cooperating agencies for purposes of
assisting with the environmental analysis.
This Final Environmental Impact Statement (FEIS) has been prepared pursuant to the
National Environmental Policy Act of 1969 (NEPA), as amended, and the Council on
Environmental Quality’s (CEQ) Regulations for Implementing the Procedural

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CHAPTER

INTRODUCTION

Provisions of NEPA (40 Code of Federal Regulations [CFR] Parts 1500 through 1508).
This FEIS has been prepared to address the formulation and evaluation of specific
interim surplus criteria and to identify the potential environmental effects of
implementing such criteria.
This FEIS addresses the environmental issues associated with, and analyzes the
environmental consequences of various alternatives for specific interim surplus criteria.
The alternatives addressed in this FEIS are those Reclamation has determined would
meet the purpose and need for the federal action and represent a broad range of the most
reasonable alternatives.
1.1.1

PROPOSED FEDERAL ACTION

The proposed federal action is the adoption of specific interim surplus criteria pursuant
to Article III(3)(b) of the Criteria for Coordinated Long-Range Operation of the
Colorado River Reservoirs Pursuant to the Colorado River Basin Project Act of
September 30, 1968 (Long-Range Operating Criteria [LROC]). The interim surplus
criteria would be used annually to determine the conditions under which the Secretary
may declare the availability of surplus water for use within the states of Arizona,
California and Nevada. The criteria must be consistent with both therDecree entered by
ior
n California
Iv. te 17 and the
e
the United States Supreme Court in 1964 in the case of Arizona
of th 29, 20
LROC. The interim surplus criteria would remainept.
in effect forrdeterminations made
. D of mbe
through calendar year 2015 regardingatioavailability vesurplus water through calendar
the n v
No
year 2016, subject to five-yearajo N conducted concurrently with LROC reviews,
v reviews ived on
n Na as part
and would be applied each year , archof the Annual Operating Plan (AOP).
ted i
4

ci
1686
. 141.1.2 BACKGROUND
No

Pursuant to Article II(B)2 of the Decree, if there exists sufficient water available in a
single year for pumping or release from Lake Mead to satisfy annual consumptive use
in the States of California, Nevada, and Arizona in excess of 7.5 million acre-feet (maf),
such water may be determined by the Secretary to be available as “surplus” water. The
Secretary is authorized to determine the conditions upon which such water may be
made available. The Colorado River Basin Project Act of 1968 (CRBPA) directs the
Secretary to adopt criteria for coordinated long-range operation of reservoirs on the
Colorado River in order to comply with and carry out the provisions of the Colorado
River Compact of 1922 (Compact), the Colorado River Storage Project Act of 1956
(CRSPA), the Boulder Canyon Project Act of 1928 (BCPA) and the United
States-Mexico Water Treaty of 1944 (Treaty). These criteria are the LROC, described
in detail later in this chapter and reproduced in Attachment A. The Secretary sponsors a
formal review of the LROC every five years.
The LROC provide that the Secretary will determine the extent to which the reasonable
consumptive use requirements of mainstream users in Arizona, California and Nevada
(the Lower Division states) can be met. The LROC define a normal year as a year in

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which annual pumping and release from Lake Mead will be sufficient to satisfy 7.5 maf
of consumptive use in accordance with the Decree. A surplus year is defined as a year
in which water in quantities greater than normal (i.e., greater than 7.5 maf) is available
for pumping or release from Lake Mead pursuant to Article II(B)2 of the Decree after
consideration of relevant factors, including the factors listed in the LROC. Surplus
water is available to agencies which have contracted with the Secretary for delivery of
surplus water, for use when their water demand exceeds their basic entitlement, and
when the excess demand cannot be met within the basic apportionment of their state.
Water apportioned to, but unused by one or more Lower Division states can be used to
satisfy beneficial consumptive use requests of mainstream users in other Lower
Division states as provided in Article II(B)(6) of the Decree.
Pursuant to the CRBPA, the LROC are utilized by the Secretary, on an annual basis, to
make determinations with respect to the projected plan of operations of the storage
reservoirs in the Colorado River Basin. The AOP is prepared by Reclamation, acting on
behalf of the Secretary, in consultation with representatives of the Colorado River Basin
states (Basin States) and other parties, as required by federal law. The interim surplus
criteria would serve to implement the provisions of Article III(3)(b) of the LROC on an
annual basis in the determinations made by the Secretary as part of the AOP process.

ior
Inter 17
1.1.3 PURPOSE OF AND NEED FOR ACTION
0
f the
pt. o er 29, 2
e
D
b
To date, the Secretary has applied factors, n v.
to those found
tio including but m
aannual on Novenot limited availability of in
N
Article III(3)(b)(i-iv) of the LROC, in
vajo
ed determinations of the
surplus quantities of water for pumpingior release from Lake Mead. As a result of
in Na 4, arch v
ted 6 and
c experience86 through preparation of AOPs, particularly during recent
actual operating i
-1
o. 14
years when there has been increasing demand for surplus water, the Secretary has
N
determined that there is a need for more specific surplus criteria, consistent with the
Decree and applicable federal law, to assist in the Secretary’s annual decision making
during an interim period.
For many years, California has been diverting more than its normal 4.4 maf
apportionment. Prior to 1996, California utilized unused apportionments of other
Lower Division states that were made available by the Secretary. Since 1996,
California has also utilized surplus water made available by Secretarial determination.
California is in the process of developing the means to reduce its annual use of
Colorado River water to 4.4 maf. Arizona is approaching full use of its apportionment
and Nevada was expected to reach its apportionment in 2000.
Additionally, through adoption of specific interim surplus criteria, the Secretary will be
able to afford mainstream users of Colorado River water, particularly those in
California who currently utilize surplus flows, a greater degree of predictability with
respect to the likely existence, or lack thereof, of surplus conditions on the river in a
given year. Adoption of the interim surplus criteria is intended to recognize
California’s plan to reduce reliance on surplus deliveries, to assist California in moving

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toward its allocated share of Colorado River water, and to avoid hindering such efforts.
Implementation of interim surplus criteria would take into account progress, or lack
thereof, in California’s efforts to achieve these objectives. The surplus criteria would
be used to identify the specific amount of surplus water which may be made available in
a given year, based upon factors such as the elevation of Lake Mead, during a period
within which demand for surplus Colorado River water will be reduced. The increased
level of predictability with respect to the prospective existence and quantity of surplus
water would assist in planning and operations by all entities that receive surplus
Colorado River water pursuant to contracts with the Secretary.
1.1.4

RELATIONSHIP TO THE UNITED STATES-MEXICO WATER
TREATY

Under Article 10(a) of the Treaty, the United Mexican States (Mexico) is entitled to an
annual amount of 1.5 maf of Colorado River water. Under Article 10(b) of the Treaty,
Mexico may schedule up to an additional 0.2 maf when “there exists a surplus of waters
of the Colorado River in excess of the amount necessary to satisfy uses in the United
States.” This is in addition to surplus determinations for the Lower Division states
made pursuant to Article II(2)(b) of the Decree and Article III(3)(B) of the LROC. The
proposed action is not intended to identify, or change in any manner,rconditions when
ior
Inte surplus
Mexico may schedule this additional 0.2 maf. Under current e
f th practice, 017
2
pt o er 2 control releases are
declarations under the Treaty for Mexico are declared .when flood 9,
D
.aree emb this practice.
made. Modeling assumptions used ination v
this EIS
based
Nov upon
Reclamation is currently engaged in discussions with Mexico through the IBWC on the
ajo N ived on
av
effects of the proposedn N 4, arch
d i action.
te

ci
86
4-16
. 1COOPERATING AGENCIES
1.1.5 LEADNo
AND

The Secretary is vested with the responsibility of managing the mainstream waters of
the lower Colorado River pursuant to federal law. This responsibility is carried out
consistent with the Law of the River. Reclamation, as the agency that is designated to
act on the Secretary’s behalf with respect to these matters, is the Lead Federal Agency
for the purposes of NEPA compliance for the development and implementation of the
proposed interim surplus criteria.
The NPS and the USIBWC are cooperating agencies for purposes of assisting with the
environmental analysis. The NPS administers three areas of national significance along
the Colorado River: Glen Canyon National Recreation Area (GCNRA), Grand Canyon
National Park and Lake Mead National Recreation Area (LMNRA). The NPS
administers recreation, cultural and natural resources in these areas from offices at Page
and Grand Canyon National Park, Arizona and Boulder City, Nevada, respectively. The
NPS also grants and administers concessions for the operation of marinas and other
recreation facilities at Lake Powell and Lake Mead.

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CHAPTER 1

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The International Boundary and Water Commission United States and Mexico (IBWC)
is a bi-national organization responsible for administration of the provisions of the
Treaty, including the Colorado River waters allocated to Mexico, protection of lands
along the Colorado River from floods by levee and floodway projects, resolution of
international boundary water sanitation and other water quality problems, and
preservation of the river as the international boundary. The IBWC consists of the
United States Section and the Mexico Section, which have their headquarters in the
adjoining cities of El Paso, Texas and Ciudad Juarez, Chihuahua, respectively.

1.2 SUMMARY OF CONTENTS OF THIS FEIS
Following is a brief description of the topics presented in the three volumes that
comprise this FEIS, including a summary of the chapters in Volume I.
Volume I of this FEIS (this volume) describes the proposed action, the alternatives
considered, the analysis of potential effects of interim surplus criteria on Colorado
River operation and associated resources, and environmental commitments associated
with the action alternatives. The contents of the chapters in this volume are as follows:
Chapter 1, Introduction, includes the following: identification of the rior
e purpose of and
Intinformation
need for the interim surplus criteria being considered; background
017
f the
concerning the apportionment of Colorado River water and therphysical facilities
pt. o e 29, 2
. De
b
associated with the Colorado River system; and discussion of the institutional
ion v Novem
at is managed. Chapter 1 also discusses
framework within which the vajosystem ed on
river N
Na thatarchiavrelationship to the proposed interim surplus
n
previous and ongoing iactions , have
cited 16864
criteria.
4-

No.

1

Chapter 2, Description of Alternatives, describes the process of formulating alternatives
and presents the reservoir operation strategies of each alternative under consideration.
A summary table of potential environmental consequences of action alternatives is
provided at the end of Chapter 2.
Chapter 3, Affected Environment and Environmental Consequences, presents the
analysis of baseline conditions along with potential impacts that could result from
implementation of the interim surplus criteria alternatives under consideration. The
discussion addresses both the affected environment (existing conditions within the area
of potential effect) and environmental consequences (potential effects of the interim
surplus criteria alternatives that could occur as compared to baseline projections). Also
discussed, in Section 3.17, are environmental commitments that Reclamation would
undertake if interim surplus criteria are implemented.
Chapter 4, Other NEPA Considerations, discusses cumulative impacts, the relationship
between short-term use and long-term productivity, and irreversible and irretrievable
commitments of resources affected by the interim surplus criteria under consideration.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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Chapter 5, Consultation and Coordination, describes the public involvement process,
including public notices, scoping meetings, and hearings. This chapter also describes
the coordination with federal and state agencies, Indian Tribes, and Mexico during the
preparation of this document and any permitting or approvals that may be necessary for
implementation of proposed interim surplus criteria.
In addition to the above, Volume I includes a list of acronyms used throughout this
document, a glossary of commonly used terms, a list of references cited in the FEIS, a
list of persons contributing to the preparation of the FEIS, a distribution list of agencies,
organizations and persons receiving copies of the document, and an index.
Volume II contains attachments which are comprised of documents and other
supporting material that provide detailed historical background and/or technical
information concerning this proposed action.
Volume III contains reproductions of letters from the public resulting from the public
review of the Draft Environmental Impact Statement (DEIS) and Reclamation’s
responses to the comments received.

r
1.3 WATER SUPPLY MANAGEMENT AND ALLOCATION
terio

e In
o th 29 2017
.thef Colorado,River Basin from
This section summarizes the water supply availablept
De in mber
n of
natural runoff, its distribution under the iLaw v. the River, and the reservoirs and
at o
Nove
diversion facilities through which the waterd on is administered from Lake Powell to
ajo N ive supply
Nav
Mexico.
d in 64, arch
cite 168
141.3.1 COLORADO RIVER SYSTEM WATER SUPPLY
No.
The Colorado River serves as a source of water for irrigation, domestic and other uses
in the States of Arizona, California, Colorado, Nevada, New Mexico, Utah and
Wyoming and in Mexico. The Colorado River also serves as a source of water for a
variety of recreational and environmental benefits.
The Colorado River Basin is located in the southwestern
United States, as shown on Map 1-1, and occupies a total
area of approximately 250,000 square miles. The
Colorado River is approximately 1400 miles in length and
originates along the Continental Divide in Rocky Mountain
National Park in Colorado. Elevations in the Colorado
River Basin range from sea level to over 14,000 feet above
mean sea level (msl) in the mountainous headwaters.
Figure 1-1 Loc ations of Lee F err y and Lees Ferr y

Climate varies significantly throughout the Colorado River
Basin. Most of the Basin is comprised of desert

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
1-6

Figure 1-1
Locations of Lee Ferry and Lees Ferry

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Map 1-1 Colorado River Drainage Basin

ior
Inter 17
0
f the
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or semi-arid rangelands, which generally receive less than 10 inches of precipitation per
year. In contrast, many of the mountainous areas that rim the northern portion of the
Basin receive, on average, over 40 inches of precipitation per year.
Most of the total annual flow in the Colorado River Basin is a result of natural runoff
from mountain snowmelt. Because of this, natural flow is very high in the late spring
and early summer, diminishing rapidly by mid-summer. While flows in late summer
through autumn sometimes increase following rain events, natural flow in the late
summer through winter is generally low. Major tributaries to the Colorado River
include the Green, San Juan, Yampa, Gunnison and Gila Rivers.
The annual flow of the Colorado River varies considerably from year to year. The
natural flow at the Lees Ferry gaging station (see Figure 1-1), located 17 river miles
(RMs) below Glen Canyon Dam, has varied annually, from 5 maf to 23 maf. Natural
flow represents an estimate of flows that would exist without reservoir regulation,
depletion, or transbasin diversion by man.
Most of the lower Colorado River’s water, or about 88 percent of the annual natural
supply, flows into the Lower Basin from the Upper Basin and is accounted for at Lee
Ferry, Arizona. The remaining 12 percent of the lower Colorado River’srwater is
erio
attributed to sidewash inflows due to rainstorms and tributarye Int in the 7
h rivers 201 Lower Basin.
of t
The Lower Colorado River Basin’s mean annual tributary inflow is ,
ept. ber 29 about 1.38 maf,
.D
m
excluding the intermittent Gila River inflow.vActual tributary inflows are highly
ation on Nove
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variable from year to year. vajo
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1.3.2 APPORTIONMENT OF WATER SUPPLY
-1
o. 14
N

This section summarizes the Colorado River apportionments of the Basin States and
Mexico stemming from the Law of the River, past and current river diversions and
consumptive use and projected future depletions. The apportionments of the Basin
States are stipulated in terms of consumptive use, which consists of diversions minus
return flows to the river system.
1.3.2.1 THE LAW OF THE RIVER
As stated previously, the Secretary is vested with the responsibility to manage the
mainstream waters of the lower Colorado River pursuant to applicable federal law. The
responsibility is carried out consistent with a body of documents referred to as the Law
of the River. The Law of the River encompasses numerous operating criteria,
regulations and administrative decisions included in federal and state statutes, interstate
compacts, court decisions and decrees, an international treaty, and contracts with the
Secretary.

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Particularly notable among these documents are:
1) The Colorado River Compact of 1922, which apportioned beneficial
consumptive use of water among the Upper and Lower Basins; The Boulder
Canyon Project Act of 1928 (BCPA), which authorized construction of
Hoover Dam and the All-American Canal (AAC), also authorized the Lower
Division states to enter into an agreement apportioning the water, required that
water users in the Lower Basin have a contract with the Secretary, and
established the responsibilities of the Secretary to direct, manage and
coordinate the operation of Colorado River dams and related works in the
Lower Basin;
2) The California Seven Party Water Agreement of 1931, which established the
relative priorities of rights among major users of Colorado River water in
California who claimed rights at that time;
3) The United States-Mexico Water Treaty of 1944 and subsequent specific
applications through minutes of the IBWC related to the quantity and quality
of Colorado River water delivered to Mexico;

rior

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4) The Upper Colorado River Basin Compact of 1948), which apportioned the
f the 9, 2017
o
Upper Basin water supply;
2
ept.

.D
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ion vAct Novem
5) The Colorado River Storageat
jo N Project on of 1956 (CRSPA), which authorized a
Nava archived
comprehensive water development plan for the Upper Basin that included the
in
cited 1686Canyon Dam;
construction of Glen 4,
14No. United States Supreme Court Decree, Arizona v. California
6) The 1964
(Decree), which confirmed the apportionment of the Lower Basin tributaries
was reserved for the exclusive use of the states in which the tributaries are
located; confirmed the Lower Basin mainstem apportionments of 4.4 maf for
use in California, 2.8 maf for use in Arizona and 0.3 maf for use in Nevada;
addressed the reservation of water for American Indian (Indian) reservations
and other federal reservations in California, Arizona and Nevada; and
confirmed the significant role of the Secretary in managing the mainstream of
the Colorado River within the Lower Basin;
7) The Colorado River Basin Project Act of 1968,which authorized construction
of a number of water development projects including the Central Arizona
Project (CAP) and required the Secretary to develop the LROC;
8) The Colorado River Basin Salinity Control Act of 1974, which authorized a
number of salinity control projects and provided a framework to improve and
meet salinity standards for the Colorado River in the United States and
Mexico; and

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9) The Grand Canyon Protection Act of 1992, which addressed the protection of
resources in Grand Canyon National Park and Glen Canyon National
Recreation Area.
Documents which are generally considered as part of the Law of the River include, but
are not limited to, documents listed in Table 1-1. Among other provisions of applicable
federal law, NEPA and the Endangered Species Act (ESA) provide a statutory overlay
on certain actions taken by the Secretary. For example, as noted in Section 1.1,
preparation of this FEIS has been undertaken pursuant to NEPA.
1.3.2.2 APPORTIONMENT PROVISIONS
The initial apportionment of water from the
Map 1-2
Upper and Lower Basins
Colorado River was determined as part of the
of the Colorado River
1922 Colorado River Compact. The Compact
divided the Colorado River into two
sub-basins, the Upper Basin and the Lower
Basin (see Map 1-2). The Upper Basin
includes those parts of the States of Colorado,
Utah, Wyoming, Arizona and New Mexico
ior
Inter 17
within and from which waters drain naturally
0
f the
into the Colorado River above Lee Ferry
pt. o er 29, 2
e
D
mb
(Arizona). The Lower Basin includes those v.
ation on Nove
oN
parts of the States of Arizona, California, ed
avaj rchiv
NUtah within and
Nevada, New Mexico iand
a
d n
citenaturally 64, into the
from which waters
168drain
14Colorado River system below Lee Ferry
No.
(Arizona). The Compact also divided the
seven Basin States into the Upper Division
and the Lower Division (see Map 1-3). The
Upper Division consists of the states of
Wyoming, Utah, Colorado and New Mexico.
The Lower Division consists of the states of
Arizona, California and Nevada.

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Table 1-1
Documents Included in the Law of the River
The River and Harbor Act, March 3, 1899
The Reclamation Act of June 17, 1902
Reclamation of Indian Lands in Yuma, Colorado
River and Pyramid Lake Indian Reservations Act
of April 21, 1904
Yuma Project authorized by the Secretary of the
Interior on May 10, 1904, pursuant to Section 4 of
the Reclamation Act of June 17, 1902
Warren Act of February 21, 1910
Protection of Property Along the Colorado River
Act of June 25, 1910
Patents and Water-Right Certificates Acts of
August 9, 1912 and August 26, 1912
Yuma Auxiliary Project Act of January 25, 1917
Availability of Money for Yuma Auxiliary Project
Act of February 11, 1918
Sale of Water for Miscellaneous Purposes Act of
February 25, 1920
Federal Power Act of June 10, 1920
The Colorado River Compact of November 24,
1922
The Colorado River Front Work and Levee
System Acts of March 3, 1925 and
January 21,1927-June 28, 1946
The Boulder Canyon Project Act of December 21,
1928
The California Limitation Act of March 4, 1929
The California Seven Party Agreement of August
18, 1931
The Parker and Grand Coulee Dams
Authorization of August 30, 1935
The Parker Dam Power Project Appropriation Act
of May 2, 1939
The Reclamation Project Act of August 4, 1939
The Boulder Canyon Project Adjustment Act of
July 19, 1940
The Flood Control Act of December 22, 1944
United States-Mexico Water Treaty of February
3, 1944
Gila Project Act of July 30, 1947
The Upper Colorado River Basin Compact of
October 11, 1948
Consolidated Parker Dam Power Project and
Davis Dam Project Act of May 28, 1954
Palo Verde Diversion Dam Act of August 31,
1954
Change Boundaries, Yuma Auxiliary Project Act
of February 15, 1956

The Colorado River Storage Project Act of April
11, 1956
Water Supply Act of July 3, 1958
Boulder City Act of September 2, 1958
Report of the Special Master, Simon H. Rifkind,
Arizona v. California, et al., December 5, 1960
United States Supreme Court Decree, Arizona v.
California, March 9, 1964
International Flood Control Measures, Lower
Colorado River Act of August 10, 1964
Southern Nevada (Robert B. Griffith) Water
Project Act of October 22, 1965
The Colorado River Basin Project Act of
September 30, 1968
Criteria for the Coordinated Long Range
Operation of Colorado River Reservoirs, June 8,
1970
Supplemental Irrigation Facilities, Yuma Division
Act of September 25, 1970
Minutes 218, March 22, 1965; 241, July 14, 1972,
(replaced 218); and 242, August 30, 1973,
(replaced 241) of the International Boundary and
Water Commission, pursuant to the United
States-Mexico Water Treaty of 1944
The Colorado River Basin Salinity Control Act of
June 24, 1974
United States Supreme Court Supplemental
Decrees, Arizona v. California, January 9, 1979
and April 16, 1984
Hoover Power Plant Act of August 17, 1984
The Numerous Colorado River Water Delivery
and Project Repayment Contracts with the States
of Arizona and Nevada, cities, water districts and
individuals
Hoover and Parker-Davis Power Marketing
Contracts
Reclamation States Emergency Drought Relief
Act of 1991
Grand Canyon Protection Act of October 30,
1992
43 CFR 414 Offstream Storage of Colorado River
Water in the Lower Division States
43 CFR 417 Lower Basin Water Conservation
Measures

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The Compact apportioned to each Basin, in
perpetuity, the exclusive beneficial consumptive
use of 7.5 maf of water per year. In
addition to this apportionment, Article III(b)
gives the Lower Basin the right to increase
its beneficial consumptive use by 1.0 maf
per annum. The Compact also stipulates in
Article III(d) that the states of the Upper
Division will not cause the flow of the river
at Lee Ferry to be depleted below an
aggregate of 75 maf for any period of 10
consecutive years.

Map 1-3
Upper and Lower Division States
of the Colorado River

The Compact, in Article VII, states that
nothing in the Compact shall be construed
as affecting the obligations of the United
States to Indian Tribes. While the rights of
most tribes to Colorado River water were
subsequently adjudicated, some Tribal rights
remain unadjudicated.

ior
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of th 29, 20
1.3.2.2.1 Upper Division State Apportionments pt.
. De
ber
ion v Novem
Nat
The Compact apportioned 7.5 maf of water d on
vajo hive in perpetuity to the Upper Basin. The
a
Upper Basin Compactin N
apportioned among the four Upper Division states the following
arc
ited quantity,of consumptive use apportioned to and available for
c total 16864
percentages of the
4use each year byo. 1Upper Basin under the Upper Colorado River Basin Compact and
N the
remaining after deduction of the use, not to exceed 50,000 acre-feet (af) per annum,
made in the State of Arizona:
•

Wyoming

14.00 percent

•

Utah

23.00 percent

•

Colorado

51.75 percent

•

New Mexico

11.25 percent

Map 1- 3 U pper and Lower Di vi sion States of the C olor ado Ri ver

In 1988, a determination of Upper Basin water supply was made in Hydrologic
Determination: Water Availability from Navajo Reservoir and the Upper Colorado
River Basin for Use in New Mexico (Interior, 1989). In consideration of Article 3(d) of
the Compact and accounting for the decrease in the average natural flow of the
Colorado River since the signing of the Compact in 1922, the Determination concluded
that Upper Basin annual water depletion can reasonably be expected to reach six maf.

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1.3.2.2.2 Lower Division State Apportionments
If sufficient mainstream water is available for release, as determined by the Secretary,
to satisfy 7.5 maf of consumptive use in the Lower Division states, then the amount of
Colorado River water apportioned for consumptive use in each Lower Division state is
expressed in terms of a fixed amount in each state, subject to varying provisions at
times of surpluses or shortages. These apportionments are: California, 4.4 maf;
Arizona, 2.8 maf; and Nevada, 0.3 maf, totaling 7.5 maf. Figure 1-2 presents a
schematic of the operation of the Colorado River, primarily in the Lower Basin. The
apportionments to the Lower Division states were established by the BCPA and
confirmed by the Decree. If water apportioned for use in a Lower Division state is not
consumed by that state in any year, the Secretary may release the unused water for use
in another Lower Division state. Consumptive use by a Lower Division state includes
delivered water that is stored offstream for future use by that state or another state.
All mainstream Colorado River waters apportioned to the Lower Basin, except for a few
thousand af apportioned for use in the State of Arizona, have been fully allocated to
specific entities and, except for certain federal establishments, placed under permanent
water delivery contracts with the Secretary for irrigation or domestic use. These entities
include irrigation districts, water districts, municipalities, Indian Tribes, r
io public
Inter 17 with
e
institutions, private water companies and individuals. Federal establishments
0
of th 2 Decree
p II(D) of the 9, 2 are not
federal reserved rights established pursuant to Articlet.
e
r
be
v. D
required to have a contract with the Secretary, but the vem allocated to a federal
ation on No water
establishment is included withinjo N ved
va the apportionment of the Lower Division state in which
in Na 4, archi
the federal establishment is located.
ted

ci
1686
. 14The highest priority Colorado River water rights are present perfected rights (PPRs),
No

which the Decree defines as those perfected rights existing on June 25, 1929, the
effective date of the BCPA. The Decree also recognizes Federal Indian reserved rights
for the quantity of water necessary to irrigate all the practicably irrigable acreage on
five Indian reservations along the lower Colorado River. The Decree defines the rights
of Indian and other federal reservations to be federal establishment PPRs. PPRs are
important because in any year in which less than 7.5 maf of Colorado River water is
available for consumptive use in the Lower Division states, PPRs will be satisfied first,
in the order of their priority without regard to state lines.

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Figure 1-2
Schematic of Colorado River Releases and Diversions

Trans-basin Diversions
Evaporation
Upper Basin Uses above
Glen Canyon Dam

Evaporation

Tributary Gains above
Hoover Dam

Lower Basin Users
above Hoover Dam

ior
Inter 17
f the 9, 20
pt. o er Evaporation
Southern Nevada
2
De
mb
Users
n v.
atio
Nove
ajo N ived on
Tributary Gains below
Nav
d in 64, arch
Hoovercite
Dam
168
. 14No

Laughlin Area
NV Users

Bullhead City Area
AZ Users

CAP

MWD

California Irrigation
Districts, Other
Users

Other AZ Users

Delivery to Mexico

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Waters available to a Lower Division state within its apportionment, but having a
priority date later than June 25, 1929, have been allocated by the Secretary to water
users within that state after consultation with the state as required by the BCPA.
1.3.2.2.3 Mexico Apportionment
Mexico has an annual apportionment of 1.5 maf of Colorado River water, based on the
provisions of the Treaty. Mexico may also receive additional water under two
conditions. First, when surplus water exists in excess of the amount that can be
beneficially used by the Basin States, Mexico is apportioned up to an additional
200,000 af of water which Mexico is allowed to schedule throughout the year in
accordance with Article 15 of the Treaty. Second, when high runoff and flooding occur
on the Colorado or Gila Rivers that is substantially more than can be put to beneficial
use by the Lower Division states, such runoff flows into Mexico.
Deliveries to Mexico are subject to reduction under extraordinary drought conditions or
serious accident to the irrigation system in the United States. In such cases, deliveries
to Mexico, as provided for under the Treaty, could be reduced in proportion to the
reduction faced by users in the United States.

rior

Inte 1
As part of this NEPA documentation, international impacts are addressed in Section
f the Abroad of7
20 Major
3.16 pursuant to Executive Order 12114-Environmentalo
ept. Effects 29,
r
D
be
Federal Actions, January 4, 1997, and the n v.1, 1997 CEQ Guidelines on NEPA
tioJuly n Nov m
a(See AttachmenteB for copies of these
Analyses for Transboundary Impacts.
o
jo N
Nava archived
documents.)
in
d
cite 16864,
141.3.3 LONG-RANGE OPERATING CRITERIA
No.

The CRBPA required the Secretary to adopt operating criteria for the Colorado River by
January 1, 1970. The LROC, adopted in 1970 (see Attachment A), control the
operation of the Colorado River reservoirs in compliance with requirements set forth in
the Compact, the CRSPA, the BCPA, the Treaty and other applicable federal laws.
Under the LROC, the Secretary makes annual determinations in the AOP (discussed in
the following section) regarding the availability of Colorado River water for deliveries
to the Lower Division states (Arizona, California and Nevada). A requirement to
equalize the active storage between Lake Powell and Lake Mead when there is
sufficient storage in the Upper Basin is also included in the LROC, as required by the
CRBPA. A more complete discussion of this concept is presented in Section 1.4.2 of
this document.
Section 602 of the CRBPA, as amended, provides that the LROC can only be modified
after correspondence with the governors of the seven Basin States and appropriate
consultation with such state representatives as each governor may designate. The
LROC call for formal reviews at least every five years. The reviews are conducted as a
public involvement process and are attended by representatives of federal agencies, the

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seven Basin States, Indian Tribes, the general public including representatives of the
academic and scientific communities, environmental organizations, the recreation
industry and contractors for the purchase of federal power produced at Glen Canyon
Dam. Past reviews have not resulted in any changes to the criteria.
1.3.4

ANNUAL OPERATING PLAN

The CRBPA requires preparation of an AOP for the Colorado River reservoirs that
guides the operation of the system for the water year. The AOP describes how
Reclamation will manage the reservoirs over a 12-month period, consistent with the
LROC and the Decree. The AOP is prepared annually by Reclamation in cooperation
with the Basin States, other federal agencies, Indian tribes, state and local agencies and
the general public, including governmental interests as required by federal law. As part
of the AOP process, the Secretary makes annual determinations regarding the
availability of Colorado River water for deliveries to the Lower Division states as
described below.
1.3.4.1 NORMAL, SURPLUS AND SHORTAGE DETERMINATIONS
The Secretary is required to determine when normal, surplus or shortagerconditions
rio
occur in the lower Colorado River, based on various factors he Inte storage and
including
t
017
hydrologic conditions in the Colorado River Basin. pt. of
29, 2
e

v. D v ber
ion determinesem sufficient mainstream water
at
Normal conditions exist when the Secretary on No that
a o N ved
vof jannual iconsumptive use in the Lower Division states.
is available to satisfy 7.5 Na
maf
h
ed in its 4, arc
ituse all of 86apportioned water for the year, the Secretary may allow
c
If a state will not
-16
other states of No. 14 Division to use the unused apportionment, provided that the
the Lower
use is covered under a contract with the consuming entity.

Surplus conditions exist when the Secretary determines that sufficient mainstream water
is available for release to satisfy consumptive use in the Lower Division states in excess
of 7.5 maf annually. This excess consumptive use is surplus and is distributed for use in
California, Arizona and Nevada in allocations of 50, 46 and four percent, respectively.
As stated above, if a state will not use all of its apportioned water for the year, the
Secretary may allow other states of the Lower Division to use the unused
apportionment, provided that the use is covered under a contract with the consuming
entity. Surplus water under the Decree, for use in the Lower Division states, was made
available by the Secretary in calendar years 1996, 1997, 1998, 1999 and 2000.
Deliveries of surplus water to Mexico in accordance with the Treaty were made in
calendar years 1983-1988, 1997, 1998, 1999 and 2000.
Shortage conditions exist when the Secretary determines that insufficient mainstream
water is available to satisfy 7.5 maf of annual consumptive use in the Lower Division
states. When making a shortage determination, the Secretary must consult with various

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parties as set forth in the Decree and consider all relevant factors as specified in the
LROC (described above), including Treaty obligations, the priorities set forth in the
Decree, and the reasonable consumptive use requirements of mainstream water users in
the Lower Division. The Secretary is required to first provide for the satisfaction of the
PPRs in the order of their priority, then to users who held contracts on September 30,
1968 (up to 4.4 maf in California), and finally to users who had contracted on
September 30, 1968, when the CAP was authorized. To date, a shortage has never been
determined.
1.3.5

SYSTEM RESERVOIRS AND DIVERSION FACILITIES

The Colorado River system contains numerous reservoirs that provide an aggregate of
approximately 60 maf of active storage. Lake Powell and Lake Mead provide
approximately 85 percent of this storage.
Upper Basin reservoirs provide approximately 31.2 maf of active storage, of which
Lake Powell provides 24.3 maf. The other major storage reservoirs in the Upper Basin
include Flaming Gorge Reservoir on the Green River, Navajo Reservoir on the San Juan
River, and Blue Mesa Reservoir on the Gunnison River.

rior

The Lower Basin dams and reservoirs include Hoover, Davis e InParker dams, shown
and te
f th to 9, 2017of active
on Map 1-4. Hoover Dam created Lake Mead and can store up 2 26.2 maf
pt. o er
. De to re-regulate Hoover Dam’s
storage. Davis Dam was constructed byion v
Reclamation emb
at of 1.5 n NovMexico. Davis Dam creates
releases and to aid in the annual jdelivery d o maf to
oN
Navamafrofhive storage. Parker Dam forms Lake Havasu
Lake Mohave and provides 1.8 a c active
in
cit isd 168 by ,
from which water e pumped 64 both Metropolitan Water District of Southern
14California (MWD) and the CAP. Parker Dam re-regulates releases from Davis Dam
No.
and from the United States Army Corps of Engineers’ (Corps) Alamo Dam on the Bill
Williams River, and in turn releases water for downstream use in the United States and
Mexico. Other Lower Basin mainstream reservoirs, listed in Table 1-2, are operated
primarily for the purpose of river flow regulation to facilitate diversion of water to
Arizona, California and Mexico. Diversion facilities of the Lower Division states
typically serve multiple entities.

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Map 1-4
Lower Colorado River Dams

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Table 1-2 summarizes the Colorado River storage facilities (i.e., dams and reservoirs)
and major diversion dams from Lake Powell downstream to Morelos Dam. Attachment
C, Dams and Reservoirs Along the Lower Colorado River, describes the reservoirs and
the role that each plays in the operation of the Colorado River system.
Table 1-2
Colorado River Storage Facilities and Major Diversion Dams
from Lake Powell to Morelos Dam
Facility

Reservoir

Glen Canyon Dam

Lake Powell

Hoover Dam

Lake Mead

Davis Dam

Lake Mohave

Parker Dam

Lake Havasu

Headgate Rock Dam

Lake Moovalya

Morelos Dam

impoundment
Unnamed
impoundment

1

Location
Upstream of Lee Ferry,
Utah, Arizona
Nevada and Arizona near
Las Vegas, 270 miles
downstream of Glen Canyon
Dam
70 miles downstream of
Hoover Dam
150 miles downstream of
Hoover Dam
164 miles downstream of
Hoover Dam
209 miles downstream of
Hoover Dam
290 miles downstream of
Hoover Dam near Imperial
Dam
290 miles downstream of
Hoover Dam
300 miles downstream of
Hoover Dam
320 miles downstream of
Hoover Dam

Storage Capacity
(af)
24,322,000 Live
27,400,000 Live

1,818,000
648,000
N.A.

3

N.A.

3

r
terio
InN.A.3 17
Palo Verde Diversion
Unnamed
0
f the
Dam
impoundment
pt. o er 29, 2
e
v. D
Senator Wash
Senator Wash
13,800
mb
2
ation on Nove
regulating facility
Reservoir
N
vajo
ed
in Na 4, archiv
d Unnamed
Imperial Dam
1000
cite impoundment
86
4-16
1 Unnamed
Laguna Dam No.
700

1
2
3

Lake Havasu provides a relatively constant water level for pumped diversions by MWD and CAP.
Senator Wash Reservoir is an offstream reservoir with a pumping/generating plant.
Run-of-river diversion structure.

In Nevada, the State’s consumptive use apportionment of Colorado River water is used
almost exclusively for municipal and industrial (M&I) purposes. About 90 percent of
this water is diverted from Lake Mead at a point approximately five miles northwest of
Hoover Dam at Saddle Island by the Southern Nevada Water Authority (SNWA)
facilities. The remainder of Nevada’s diversion occurs below Davis Dam in the
Laughlin area.
There are several points of diversion in Arizona. Up to 50,000 af of water is diverted
above Lee Ferry. The intake for the CAP is the pumping plant on Lake Havasu below
the confluence of the Bill Williams River. Irrigation water for the Fort Mojave Indian
Reservation, near Needles, California, is pumped from wells. Irrigation water for the
Colorado River Indian Reservation near Parker, Arizona, is diverted at Headgate Rock

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Dam, which was constructed for that purpose. A river pumping plant in the Cibola area
provides water to irrigate lands adjacent to the river. The last major diversion for
Arizona occurs at Imperial Dam, where water is diverted into the Gila Gravity Main
Canal for irrigation for the Gila and Wellton-Mohawk projects and into the AAC for
subsequent release into the Yuma Main Canal for the Yuma Project and the City of
Yuma.
California receives most of its Colorado River water at three diversion points: MWD’s
pumping plant on Lake Havasu; the Palo Verde Irrigation and Drainage District’s
diversion at the Palo Verde Diversion Dam near Blythe, California; and the AAC
diversion at Imperial Dam.
1.3.6

FLOOD CONTROL OPERATION

Under the BCPA, flood control was specified as the project purpose having first priority
for the operation of Hoover Dam. Subsequently, Section 7 of the Flood Control Act of
1944 established that the Secretary of War (now the Corps) will prescribe regulations
for flood control for projects authorized wholly or partially for such purposes.
The Los Angeles District of the Corps published the current flood control regulations in
rior
the Water Control Manual for Flood Control, Hoover Dam he ILake Mead Colorado
and nte
17
ft
River, Nevada and Arizona (Water Control Manual) dated December 20
pt. o er 29, 1982. The Field
e
b
Working Agreement between Corps and on v. D
for the
i Reclamationvem flood control operation of
at by theNo Control Manual, was signed
Hoover Dam and Lake Mead, asjo N
prescribed on Water
Nava controlived is the result of a coordinated effort
on February 8, 1984. in flood arch plan
The
cited 16864,
between the Corps and -Reclamation; however, the Corps is responsible for providing
the flood controlo. 14
N regulations and has authority for final approval. The Secretary is
responsible for operating Hoover Dam in accordance with these regulations. Any
deviation from the flood control operating criteria must be authorized by the Corps.
Flood control operation of Lake Mead was established to deal with two distinct types of
flooding—snowmelt and rain. Snowmelt constitutes about 70 percent of the annual
runoff in the Upper Basin. Lake Mead’s uppermost 1.5 maf of storage capacity,
between elevations 1219.61 feet above msl and 1229.0 feet msl, are allocated
exclusively to control floods from rain events.
The flood control regulations set forth two primary criteria to deal with snowmelt:
•

Preparatory reservoir space requirements, applicable from August 1 through
December 31; and

•

Application of runoff forecasts to determine releases, applicable from January
1 through July 31.

In preparation for each year’s seasonal snow accumulation and associated runoff, the
first criterion provides for progressive expansion of the total Colorado River system

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reservoir space during the latter months of each year. Required system space increases
from 1.5 maf on August 1 to 5.35 maf on January 1. Required flood storage space up to
3.85 maf can be located within Lake Powell and in specified Upper Basin reservoirs.
Space-building releases from Lake Mead are made when needed to meet the required
August 1 to January 1 flood control space. Space-building releases beyond the
minimum requirements of the Corps’ Water Control Manual (often described as
anticipatory flood control releases) may be considered by the Secretary. The Secretary
takes into consideration the following: 1) the channel capacity of the river below Davis
Dam; 2) the channel capacity and channel maintenance of the river below the Southerly
International Boundary (SIB) (through the IBWC); and 3) power plant maintenance
requirements at Hoover, Davis and Parker dams.
Between January 1 and July 31, flood control releases, based on the maximum
forecasted inflow into Lake Mead, may be required to prevent filling of Lake Mead
beyond its 1.5 maf minimum flood control space. Each month, runoff forecasts are
developed by the National Weather Service’s Colorado Basin River Forecast Center.
The required monthly releases from Hoover Dam are determined based on available
space in Lake Mead and upstream reservoirs and the maximum forecasts of inflow into
Lake Mead. Average monthly releases are determined each month erioapply only to
and r
Int River Floodway
the current month. Release rates, developed pursuant to thehe
Colorado 017
of t
,2
Protection Act of 1986, are discussed in SectionDept.
3.6.4.1.
er 29

v.
mb
ation on Nove
1.3.7 HYDROPOWER GENERATION
jo N
Nava archived
d in
,
Reclamation is cite -16by64
authorized 8 legislation to produce electric power at each of the major
14
Colorado River system dams, except Navajo Dam. Power generation at the Glen
No.

Canyon Dam Powerplant requires the water surface elevation of Lake Powell to be
above 3490 feet msl. Water is released from Glen Canyon Dam Powerplant into the
Colorado River through a combination of the eight main generating units. The
minimum water surface elevation of Lake Mead necessary for power generation at
Hoover Powerplant is approximately 1083 feet msl. Water is released from Hoover
Powerplant to Lake Mohave through a combination of the 17 main generating units.
Water is then released at Davis Dam Powerplant into the river through a combination of
the five generators. Parker Dam is the last major regulating and reservoir facility on the
Lower Colorado River. All releases scheduled from Parker Dam are in response to
downstream water orders and reservoir regulation requirements and pass through a
combination of its four generators.
Although Reclamation is the federal agency authorized to produce power at the major
Colorado River system dams, Western Area Power Administration (Western) is the
federal agency authorized to market this power. Western enters into electric service
contracts on behalf of the United States with public and private utility systems for
distribution of hydroelectric power produced at Reclamation facilities. The released

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water generates power, but water is not to be released from any Colorado River facility
for the sole purpose of generating power.
Under operating agreements with Western, Reclamation is subject to downstream water
requirements to meet the power generation schedules of Hoover, Parker and Davis
dams. Western produces these schedules in accordance with existing electric service
contracts, recognizing Reclamation’s release requirements on the lower Colorado River
(i.e., based on downstream delivery requirements) from the respective reservoirs.

1.4 RELATED AND ONGOING ACTIONS
A number of ongoing and new actions proposed by Reclamation and other entities are
related to the development of interim surplus criteria and the analysis contained in this
document. This section describes these actions and their relationship to the
development of interim surplus criteria. The following actions have been described in
environmental documents, consultation packages under Section 7 of the ESA, or as
project planning documents. Where appropriate, this FEIS incorporates by reference
information contained in these documents. The documents described below are
available for public inspection upon request at Reclamation offices in Boulder City,
Nevada; Salt Lake City, Utah; and Phoenix and Yuma, Arizona. erior

Int
0
f the PLAN17
1.4.1 CALIFORNIA’S COLORADO RIVERept. o USE 9, 2
WATER r 2
v. D v mbe
o
ation (CA Plan),ewhich was formerly known as
California’s Colorado River Water N Plan on N
vajo Use ived
the California 4.4 Planin Na 4.4 Plan, calls for conservation measures to be put in place
or the
arch
cited 16864,
that will reduce California’s dependency on surplus Colorado River water. Surplus
4water is requiredo. 1
N to meet California’s current needs until implementation of the
conservation measures can take place. During the period ending in 2016, the State of
California has indicated that it intends to reduce its reliance on Colorado River water to
meet its water needs above and beyond its 4.4-maf apportionment. It is important for
the long-term administration of the system to bring the Lower Basin uses into
accordance with the Lower Basin normal apportionment. In order to achieve its goals,
California has expressed a need to continue to rely in some measure on the existence of
surplus Colorado River water through 2016. These interim surplus criteria could aid
California and its primary Colorado River water users as California reduces its
consumptive use to 4.4 maf while ensuring that the other Basin States will not be placed
at undue risk of future shortages.
The CA Plan contains numerous water conservation projects, intrastate water
exchanges, and groundwater storage facilities. The CA Plan is related to the
implementation of the interim surplus criteria in the ways discussed below.
First, implementation of the CA Plan is necessary to ensure the Colorado River system
can meet the normal year deliveries in the Lower Basin over the long term. Failure of
California to comply with the CA Plan places at risk the objective of providing reliable

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delivery of water for beneficial consumptive use to Lower Basin users. Therefore, the
Secretary may condition the continuation of interim surplus criteria for the entire period
through 2016 on a showing of satisfactory progress in implementing the CA Plan.
Regardless of which alternative is ultimately selected, failure of California to carry out
the CA Plan may result in termination or suspended application of the proposed interim
surplus criteria. In that event, the Secretary would fashion appropriate surplus criteria
for the remaining period through 2016. For example, the Basin States Alternative
presented in Chapter 2 anticipates that the 70R strategy would be used in the event of
such a reversion.
Second, from the perspective of the State of California, because of the linkage between
various elements of the CA Plan and the quantities of water involved, a reliable supply
of interim surplus water from the Colorado River is an indispensable pre-condition to
successful implementation of the CA Plan.
From the standpoint of environmental documentation and compliance, the CA Plan and
its various elements have been, or will be, addressed under separate federal and/or state
environmental reporting procedures.
1.4.1.1 IMPERIAL IRRIGATION DISTRICT/SAN DIEGO COUNTY WATER AUTHORITY
ior
Inter 17
ATER TRANSFER
W
the

20
of
ept. ber 29,
v. County Water Authority (SDCWA)
The Imperial Irrigation District (IID)/San DiegoD
em
ation on Nova part of the CA Plan. SDCWA
N
water transfer is one of the intrastate exchanges that is
vajo
ed
has negotiated an agreement for therlong-term transfer of conserved water from the IID.
in Na 4, a chiv
d
cite 168 IID
Under the proposed contract,6 customers would undertake water conservation efforts
to reduce theirNo. of 4
use 1 Colorado River water. Water conserved through these efforts
would be transferred to SDCWA. The agreement sets the transfer quantity at a
maximum of 200 kaf/year. After at least 10 years of primary transfers, an additional
discretionary component not to exceed 100 kaf/year may be transferred to SDCWA,
MWD of Southern California, or Coachella Valley Water District in connection with
the settlement of water rights disputes between IID and these agencies. The initial
transfer target date is 2002, or whenever the conditions necessary for the agreement to
be finalized are satisfied or waived, whichever is later. This transfer is being addressed
in an ongoing EIS/EIR and involves the change in point of delivery of up to 300
kaf/year from Imperial Dam to Parker Dam.
1.4.1.2 ALL-AMERICAN AND COACHELLA CANAL LINING PROJECTS
Two other components of the CA Plan having effects on the river are the
All-American and Coachella Canal Lining Projects (the Coachella Canal is a branch of
the AAC). These two similar actions involve the concrete lining of unlined portions of
the canals to conserve water presently being lost as seepage from the earthen reaches.
Together the projects involve a change in point of delivery from Imperial Dam to Parker
Dam that totals 93.7 kaf/year, 67.7 kaf/year for the AAC and 26 kaf/year for the

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Coachella Canal. The effects of this change in point of delivery are being addressed in
the Secretarial Implementation Agreement EA and BA (described in Section 1.4.5).
The Record of Decision (ROD) for the All-American Canal Lining Project was
approved on July 29, 1994. Construction is expected to begin in 2001. A draft EIS/EIR
for the Coachella Canal Lining Project was released on September 22, 2000 for public
review.
1.4.2

GLEN CANYON DAM OPERATIONS

Glen Canyon Dam is operated consistent with the CRSPA and the LROC, which were
promulgated in compliance with Section 602 of the CRBPA. Glen Canyon Dam is also
operated consistent with the 1996 ROD on the Operation of Glen Canyon Dam
(Attachment C) developed as directed under the Grand Canyon Protection Act of 1992.
The minimum release from Lake Powell, as specified in the LROC, is 8.23 maf per
year. In years with very low inflow, or in years when Lake Powell is significantly
drawn down, annual releases of 8.23 maf from Lake Powell are made. The LROC also
require that, when Upper Basin storage is greater than the storage required under
Section 602(a) of the CRBPA, releases from Lake Powell will periodically be governed
by the objective to maintain, as nearly as practicable, active storage inior Mead equal
er Lake
In provision in the
to the active storage in Lake Powell. Because of this equalization t
f the result 017
LROC, changes in operations at Lake Mead will, inpt. o years, 29, 2in changes in
some
. De
ber
annual release volumes from Lake Powell.n It is through this mechanism that delivery of
io v Novem
at
on
surplus water from Lake Meadajo N
v can influence the operation of Glen Canyon Dam.
ved
iexists insufficient storage in the Upper Basin,
Na
Equalization is not required when arch
d in 64, there
citeof the CRBPA.
per Section 602(a)
-168

No.

14

In acknowledgement that the operation of Glen Canyon Dam, as authorized, to
maximize power production was having a negative impact on downstream resources,
the Secretary determined in July 1989 that an Environmental Impact Statement (EIS)
should be prepared. The Operation of Glen Canyon Dam EIS developed and analyzed
alternative operation scenarios that met statutory responsibilities for protecting
downstream resources and achieving other authorized purposes, while protecting Native
American interests. A final EIS was completed in March 1995, and the Secretary
signed a ROD on October 8, 1996. Reclamation also consulted with the United States
Fish and Wildlife Service (Service) under the ESA and incorporated the Service’s
recommendations into the ROD.
The ROD describes criteria and plans for dam operations and includes other measures
to ensure Glen Canyon Dam is operated in a manner consistent with the Grand Canyon
Protection Act of 1992. Among these are an Adaptive Management Program,
beach/habitat-building flows (BHBFs), beach/habitat-maintenance flows, and further
study of temperature control.

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The ROD is based on the EIS, which contains descriptions and analyses of aquatic and
riparian habitats below Glen Canyon Dam, effects of Glen Canyon Dam release patterns
on the local ecology, cultural resources, sedimentation processes associated with the
maintenance of backwaters and sediment deposits along the river, Native American
interests, and relationships between release patterns and the value of hydroelectric
energy produced. Analyses of effects on other resources within the affected area are
also included. Additional information concerning the operation of Glen Canyon Dam is
contained in Section 3.3.
1.4.2.1

ADAPTIVE MANAGEMENT PROGRAM

The Adaptive Management Program (AMP) provides a process for assessing the effects
of current operations of Glen Canyon Dam on downstream resources and using the
results to develop recommendations for modifying operating criteria and other resource
management actions. This is accomplished through the Adaptive Management Work
Group (AMWG), a federal advisory committee. The AMWG consists of stakeholders
that are federal and state resource management agencies, representatives of the seven
Basin States, Indian Tribes, hydroelectric power marketers, environmental and
conservation organizations and recreational and other interest groups. The duties of the
r
AMWG are in an advisory capacity only. Coupled with this advisory irole are long-term
ter o
Inof resource conditions
e
monitoring and research activities that provide a continual record
of th 29 2017
and new information to evaluate the effectiveness epthe operational, modifications.
of t.
D
er

v.
mb
t on
aFiLOWSon Nove /HABITAT-MAINTENANCE
1.4.2.2 BEACH/HABITAT-Bvajo N
a UILDINGhived AND BEACH
FLOWS ed in N
arc
cit
864,
-16
BHBF releases are scheduled high releases of short duration that are in excess of power
o. 14
N
plant capacity required for dam safety purposes and are made according to certain
specific criteria as described in Section 3.6.2. These BHBFs are designed to rebuild
high elevation sandbars, deposit nutrients, restore backwater channels, and provide
some of the dynamics of a natural system. The first test of a BHBF was conducted in
Spring of 1996.

Beach/habitat-maintenance flow releases are releases at or near power plant capacity,
which are intended to maintain favorable beach and habitat conditions for recreation
and fish and wildlife, and to protect Tribal interests. Beach/habitat-maintenance flow
releases can be made in years when no BHBF releases are made.
Both beach/habitat-building and beach/habitat-maintenance flows, along with the
testing and evaluation of other types of releases under the AMP, were recommended by
the Service to verify a program of flows that would improve habitat conditions for
endangered fish. The proposed interim surplus criteria could affect the range of storage
conditions in Lake Powell and alter the flexibility to schedule and conduct such releases
or to test other flow patterns. The magnitude of this reduction in flexibility has been

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evaluated for each interim surplus alternative. The results are presented in Section 3.6,
Riverflow Issues.
1.4.2.3

TEMPERATURE CONTROL AT GLEN CANYON DAM

In 1994, the Service issued a Biological Opinion on the Operation of Glen Canyon
Dam. One of the elements of the reasonable and prudent alternative in the Biological
Opinion, also a common element in the Glen Canyon Dam EIS, was the evaluation of
methods to control release temperatures and, if viable, implement controls.
Reclamation agreed with this recommendation and included it in the Operation of Glen
Canyon Dam Final Environmental Impact Statement and subsequent ROD.
Reclamation has issued a draft planning report and environmental assessment (EA)
entitled Glen Canyon Dam Modifications to Controls and Downstream Temperatures
(Reclamation, 1999). Based on comments to this draft EA, Reclamation is currently in
the process of preparing a new draft EA on temperature control at Glen Canyon Dam.
Interim surplus criteria could result in new information related to temperature control at
Glen Canyon Dam. Data and information made available from analysis related to
interim surplus criteria will be utilized in the revised EA on temperaturercontrol at Glen
rio
Canyon Dam. Such information would also be considered in e Inte
h the development of an
t
017
appropriate design for a temperature control device.pt. of
29, 2
e

.D
ber
ion v NovemAND CONFERENCE
1.4.3 ACTIONS RELATED jo Nat BIOLOGICAL
a TO THE d on
OPINION ONn Nav COLORADO RIVER OPERATIONS AND
LOWER rchive
i
a
cited 16
MAINTENANCE 864,
14No. a Biological Assessment (BA) in accordance with Section 7 of
Reclamation prepared

the ESA, addressing effects of ongoing and projected routine lower Colorado River
operations and maintenance (Reclamation, 1996). After formal consultation, a
Biological and Conference Opinion (BCO) was prepared by the Service (Service,
1997). Both documents are described in Section 1.4.5, Documents Incorporated by
Reference. Pursuant to the reasonable and prudent alternative and 17 specific
provisions provided in the BCO, Reclamation is taking various actions that benefit the
riparian region of the lower Colorado River and associated species. In particular, these
actions include: 1) acquisition, restoration, and protection of potential and occupied
Southwestern willow flycatcher habitat; 2) extensive life history studies for
Southwestern willow flycatcher along 400 miles of the lower Colorado River and other
areas; and 3) protection and enhancement of endangered fish species through risk
assessments, assisted rearing, and development of protected habitats along the lower
Colorado River. This five-year BCO provides ESA compliance for Reclamation actions
on the lower Colorado River until 2002.
The BA and BCO contain life histories/status of lower Colorado River species,
descriptions of ongoing and projected routine operation and maintenance activities, the

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Secretary’s discretionary management activities, operation and maintenance (O&M)
procedures, endangered species conservation program, environmental baseline, effects
of ongoing operations, reasonable and prudent alternatives, and supporting
documentation useful in this FEIS. The 1996 BA and the 1997 BCO did not anticipate
or address the effects of specific interim surplus criteria on the species considered. A
separate Section 7 ESA consultation is in progress for the proposed action addressed by
this FEIS.
1.4.4

LOWER COLORADO RIVER MULTI-SPECIES CONSERVATION
PROGRAM

Following the designation of critical habitat for three endangered fish species on nearly
all of the lower Colorado River in April of 1994, the three Lower Basin States of
Arizona, California and Nevada, Reclamation and the Service initiated the Lower
Colorado River Multi-Species Conservation Program (LCRMSCP), which was one of
the reasonable and prudent provisions of the five-year BCO received in 1997. The
purpose of the LCRMSCP is to obtain long-term (50-year) ESA compliance for both
federal and non-federal water and power interests. The LCRMSCP is a partnership of
Federal, State, Tribal, and other public and private stakeholders with an interest in
managing the water and related resources of the lower Colorado Riverior
Basin. In August
Inter 1entered into a
e
1995, the Department of the Interior and Arizona, California and Nevada 7
of th 29, 20
Memorandum of Agreement (MOA) and later aDept.
Memorandumrof Clarification (MOC)
.
mbe
for development of the LCRMSCP. Theon v
ati purpose ofoveMOA/MOC was to initiate
N the
development of an LCRMSCPajo N ved on
av that would accomplish the following objectives:

N
rchi
d in 6
itehabitat and4, a toward the recovery of threatened and endangered
c
• Conserve 4-168 work
1
specieso. reduce the likelihood of additional species listing under the ESA;
N and
and
•

Accommodate current water diversions and power production and optimize
opportunities for future water and power development.

The LCRMSCP is currently under development, and it is anticipated that the final EISenvironmental impact report (EIR) will be finalized in 2001. Once the LCRMSCP is
accepted by the Service, Reclamation and other federal agencies, as well as the
participating non-federal partners, will have achieved ESA compliance for ongoing and
future actions.
Since the interim surplus criteria determination is scheduled to be completed prior to the
completion of the LCRMSCP, a separate Section 7 consultation has been conducted
with the Service on the anticipated effects of implementing the interim surplus criteria.

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1.4.5

SECRETARIAL IMPLEMENTATION AGREEMENT RELATED TO
CALIFORNIA’S COLORADO RIVER WATER USE PLAN

Within California, the allocation of Colorado River water is stipulated by various
existing agreements among the seven parties with diversion rights. Recently, these
parties have negotiated a Quantification Settlement Agreement which further defines the
priorities for use of Colorado River water in California. This agreement provides a
basis for various water conservation and transfer measures described in the CA Plan
(California, 2000). The water transfers would require changes in the points at which the
Secretary would deliver transferred water to various California entities, as compared
with provisions in existing water delivery contracts. The operational changes caused by
the water transfers are being addressed in separate NEPA and ESA documentation.
1.4.6

OFFSTREAM STORAGE OF COLORADO RIVER WATER AND
DEVELOPMENT AND RELEASE OF INTENTIONALLY CREATED
UNUSED APPORTIONMENT IN THE LOWER DIVISION STATES

The above titled rule establishes a procedural framework for the Secretary to follow in
rior
considering, participating in, and administering Storage andhe Inte Release
Interstate
17
t
Agreements among the States of Arizona, California,tandfNevada 9, 20 Division
p . o er 2 (Lower
. De
states). The Storage and Interstate Release Agreementsemb permit State-authorized
ion v Nov would
t
N offstream, develop intentionally created unused
entities to store Colorado River watera
on
vajoICUAvavailable to the Secretary for release for use in
Namakearchi ed
apportionment (ICUA), and
d in
,
another Lower cite -16864
Division state. This rule provides a framework only and does not
14
authorize any specific activities. The rule does not affect any Colorado River water
No.
entitlement holder’s right to use its full water entitlement, and does not deal with
intrastate storage and distribution of water. The rule only facilitates voluntary interstate
water transactions that can help satisfy regional water demands by increasing the
efficiency, flexibility, and certainty in Colorado River management. A Finding of No
Significant Impact (FONSI) was approved on October 1, 1999.

1.5 DOCUMENTS INCORPORATED BY REFERENCE
During recent decades, a considerable amount of environmental information has been
obtained and environmental analyses conducted concerning the operation of the
Colorado River water supply system. Much of this information is contained in various
documents prepared under NEPA and the ESA. These documents have been previously
distributed to interested agencies and private parties. In the interest of avoiding
duplication and undue paperwork, this FEIS incorporates by reference parts or all of
several documents. The documents described below are available for public inspection
upon request at Reclamation offices in Boulder City, Nevada; Salt Lake City, Utah;
Phoenix and Yuma, Arizona.

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•

Biological Assessment for Proposed Interim Surplus Criteria, Secretarial
Implementation Agreements for California Water Plan Components and
Conservation Measures, August 30, 2000.
This BA was prepared by Reclamation in Boulder City, Nevada, to address the
potential effects on threatened or endangered species and designated critical habitat
along the lower Colorado River attributable to the water transfers proposed by
California as part of its CA Plan and to the implementation of the proposed interim
surplus criteria. The BA was prepared to facilitate formal Section 7 consultation
with the Service, which resulted in the BO cited below addressing these proposed
actions. The pertinent parts of this BA are the ecology of aquatic and riparian
habitat systems from Lake Mead to the SIB and the potential effects of these
proposed actions on listed species and critical habitat. With regard to any potential
effects of the proposed adoption of interim surplus criteria on ESA listed species in
the Republic of Mexico or the Gulf of California, Reclamation has prepared
additional information to supplement this assessment.

•

Biological Opinion on Proposed Interim Surplus Criteria, Secretarial
Implementation Agreements for California Water Plan Components and
r
Conservation Measures, December, 2000.
terio

In
f he 9 2017
. oin tPhoenix,, Arizona, through
This Biological Opinion (BO), issued by theDept
Service
ber 2
mNevada, addresses the
n v.
formal consultation with Reclamation in Boulder City,
atio
Nove
potential effects on threatened or endangered species and designated critical habitat
ajo N ived on
av
along the lower d in N River rattributable to the water transfer agreements
Colorado 4, a ch
cite 16 as
proposed by California 86part of its CA Plan and to the implementation of interim
14surplus criteria. The BO identifies reasonable and prudent measures for the
No.
avoidance of adverse effects of these proposed actions. The pertinent parts of the
BO are the life histories of various species, their habitat descriptions, and
relationships with river operations.
•

Biological Assessment on Transboundary Effects for Proposed Interim Surplus
Criteria, December, 2000.
This BA was prepared by Reclamation in Boulder City, Nevada, to address the
potential effects on threatened or endangered species in the Colorado River Delta of
Mexico attributable to the implementation of proposed interim surplus criteria. The
BA was prepared to facilitate informal consultation with the Service and the
National Marine Fisheries Service, which is in progress. The pertinent parts of the
BA are the ecology of aquatic and riparian habitat systems from the SIB to the
estuary at the mouth of the Colorado River in the Sea of Cortez and the potential
effects of the proposed action on United States-listed species and critical habitat.

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•

Description and Assessment of Operations, Maintenance, and Sensitive Species of
the Lower Colorado River (Biological Assessment), August 1996.
This BA was prepared by Reclamation in Boulder City, Nevada, to develop an
inventory of aquatic and marsh habitat along the lower Colorado River and to
analyze the relationships between river operation and maintenance of threatened and
endangered species and critical habitat. The BA was prepared to facilitate the
formal Section 7 consultation with the Service, which resulted in the April 1997
BCO cited below. The pertinent parts of the BA are the ecology of aquatic and
riparian habitat systems from Lake Mead to the SIB and the potential effects of
ongoing operation and maintenance on listed species and critical habitat.

•

Biological and Conference Opinion on Lower Colorado River Operations and
Maintenance, April 1997.
This BCO, prepared by the Service in Phoenix, Arizona, through formal
consultation with Reclamation in Boulder City, Nevada, addresses the critical
habitat for endangered species along the lower Colorado River that is related to the
operation of the river for delivery of water to the Lower Division states and Mexico.
The report identifies a reasonable and prudent alternative for the avoidance of
or
nteri 7
Iconference and opinion
adverse effects of river operation. The pertinent partsfofhe
the
201
o t
are the life histories of various species, theirDept. descriptions, and relationships
habitat
r 29,
be
v.
with river operations.
ovem
ation

N
N
vajo hived on
n Na , r
• Operation of GleniCanyon Dam c
4 October 8, 1996.
ited of Decision,a Final Environmental Impact Statement, March
c
1995, and Record4-1686
1
No.

The FEIS was prepared by Reclamation in Salt Lake City, Utah, to evaluate
alternative plans for the water releases at Glen Canyon Dam and Powerplant and the
ecological effects on the Colorado River corridor downstream to Separation Rapid.
The FEIS was based on an extraordinary depth of analysis, involving numerous
work groups with specialists in various disciplines from other agencies and private
practice. The pertinent parts of the FEIS are the aquatic and riparian habitats below
Glen Canyon Dam, the relationships between Glen Canyon Dam and Powerplant
release patterns, effects on downstream ecology, and the sedimentation processes
associated with the maintenance of backwaters and beaches along the river. The
relationships between release patterns and the value of hydroelectric energy
produced were also pertinent.
The ROD adds commitments in the following areas: establishment of an AMP,
monitoring and protecting cultural resources, flood frequency reduction measures,
BHBF releases, efforts to establish a new population of the humpback chub, further
study of selective withdrawals from Lake Powell, and emergency exception criteria
to respond to various emergency situations.

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CHAPTER 1

INTRODUCTION

•

Glen Canyon Dam Modification to Control Downstream Temperatures Plan and
Environmental Assessment, January 1999 Draft.
This draft planning report and EA was prepared by Reclamation in Salt Lake City,
Utah, to consider alternatives for modifying the intakes to the penstocks to permit
the selective withdrawal of water from Lake Powell at various temperatures. The
pertinent parts of the report are the sensitivity of downstream fish species,
particularly endangered species, to temperatures of Colorado River water
downstream from the dam and the degree of temperature control that could be
achieved by the modifications. Based on comments on the draft EA, Reclamation is
in the process of preparing a new draft EA on temperature control at Glen Canyon
Dam.

•

Final Biological Opinion, Operation of Glen Canyon Dam as the Modified Low
Fluctuating Flow Alternative, December 1994.
This Biological Opinion was prepared by the Service in Phoenix, Arizona, through
consultation with Reclamation in Salt Lake City, Utah. The document addresses
Glen Canyon Dam operations and the critical habitat for endangered species in the
Colorado River from Glen Canyon Dam to Lake Mead and identifies a reasonable
ior
Inter 1also provides
e
and prudent alternative for the avoidance of jeopardy.f The document 7
20
o th area related to the
environmental baseline and status of speciesDethe. actioner 29,
in pt
b
v.
preferred alternative.
ovem
ation

N
N
vajo hived on
in Na
rc
• Glen Canyon Adaptive Management Work Group Charter, December 8, 1998.
ited 6864, a
c
-1
This charter outlines the membership and duties of the AMWG. The duties are to
o. 14
N

establish AMWG operating procedures, advise the Secretary in meeting
environmental and cultural commitments of the Glen Canyon Dam FEIS and ROD,
recommend a framework for AMP policy, goals and direction; develop
recommendations for modifying dam operations and operating criteria; define and
recommend resource management objectives for a long-term monitoring plan;
review and provide input to the Secretary on required reports; facilitate input and
coordination of information from stakeholders to the Secretary; and monitor and
report on compliance of all program activities with applicable laws, permitting
requirements, and the Grand Canyon Protection Act.

•

Quality of Water, Colorado River Basin, Progress Report No. 19, January 1999.
This report is the latest of a series of biennial reports to Congress, prepared by
Reclamation in Salt Lake City, Utah, that summarize progress of the Colorado River
Water Quality Improvement Program in controlling Colorado River salinity. The
pertinent parts of the report are those which discuss the mechanisms that contribute
dissolved salts to the river system, the relationships between dissolved salt

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concentrations and abundance of basin water supply, and the effects of dissolved
minerals on uses of Colorado River water.
•

Southern Nevada Water Authority Treatment and Transmission Facility Final
Environmental Impact Statement, September 1996, and Record of Decision,
November 1996.
This EIS and ROD contain pertinent information concerning the influence of Las
Vegas Valley drainage on the water quality in Lake Mead’s Boulder Basin and the
resulting quality of water pumped from the reservoir by the SNWA’s intake
facilities. Critical intake elevations are identified in the documents.

•

Final Programmatic Environmental Assessment for Rulemaking for Offstream
Storage of Colorado River Water and Development and Release of Intentionally
Created Unused Apportionment in the Lower Division States, October 1999.
This document, which includes a BA, analyzes the environmental effects of
potential changes in reservoir and river operations that could occur if a Lower
Division state diverts and stores water for the benefit of another Lower Division
state for future use (interstate offstream storage). The BA containsor
aquatic and
eri
marsh habitat descriptions and the relationships betweenhe Int in diversions from
changes 17
0
f t marsh habitat
Lake Mead and Lake Havasu and downstreamept. o and r 29, 2
aquatic
D
mbe
maintenance. The relationships between v.
n release patterns from
atiouseful for oveanalysis. Hoover Dam and the
N this
value of hydroelectric energyo Nalso ed on
vaj are

in Na
rchiv
ited 6864, a
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o. 14
N

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ior
Inter 17
0
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pt. o er 29, 2
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cited 16864,
14No.

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2

DESCRIPTION OF ALTERNATIVES

2.1 INTRODUCTION
This chapter discusses the process used to define the No Action Alternative and develop
a range of reasonable interim surplus criteria alternatives, and summarizes various
alternatives that were considered but eliminated from further analysis. It then describes
the alternatives analyzed in this FEIS. Modeling procedures and assumptions used to
analyze the alternatives are discussed in Section 3.3. The end of this chapter presents a
table of effects of all alternatives.

2.2 DEVELOPMENT OF ALTERNATIVES
This FEIS considers five interim surplus criteria alternatives as well as a No Action
Alternative/baseline that was developed for comparison of potential effects. The five
action alternatives considered include the Basin States Alternative (preferred
alternative), the Flood Control Alternative, the Six States Alternative, the California
Alternative, and the Shortage Protection Alternative (as described in Section 2.3).
ior
Section 2.2.1 discusses the strategies and origins of the action alternatives and describes
Inter 17
f the 9, 2
alternatives that were considered but eliminated fromtfurther analysis. 0
p.o

. De e er 2
n vSURPLUSmb
a FOR
2.2.1 OPERATING STRATEGIEStio
Nov DETERMINATION
ajo N ived on
Nav
d in 64, arch
2.2.1.1 THE R STRATEGY
cite 168
14No.
In 1986, Reclamation developed an operating strategy for distributing surplus water and
avoiding spills (Reclamation, 1986). That analysis established the Spill Avoidance or
“R” strategy. The development of this strategy was an outcome of sustained flood
control releases at Lake Mead from 1983 through 1986. The R strategy assumes a
particular percentile historical runoff, along with normal 7.5 maf delivery to Lower
Division states, for the next year. Applying these values to current reservoir storage,
the projected reservoir storage at the end of the next year is calculated. If the calculated
space available at the end of the next year is less than the space required by flood
control criteria, then a surplus condition is determined to exist.
Two alternatives considered in this FEIS use variations of the R strategy. The 70R
strategy uses an annual runoff of 17.4 maf whereas the 75R strategy uses 18.1 maf. The
70R strategy was used to represent the baseline as described in Section 2.3.1.
2.2.1.2 THE A STRATEGY
In the early and mid-1990s, Reclamation continued discussing surplus criteria strategies
with the Colorado River Management Work Group (CRMWG), which formed a
technical committee was formed to investigate additional surplus criteria strategies.

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One of the strategies developed through the CRMWG analysis was the Flood Control
avoidance or “A” strategy. This strategy determines when there is insufficient storage
space in Lake Mead and upstream reservoirs, in order to avoid flood control releases
from Lake Mead with a particular percent assurance.
The most common usage became the 70 percent assurance level (70A strategy). This
alternative was eliminated because the modeling results were so similar to the Flood
Control Alternative and the No Action/baseline (70R strategy) that it was not necessary
to analyze it.
2.2.1.3 THE P STRATEGY
Another strategy is the Shortage Protection or “P” strategy. This strategy is based on
making surplus water available while maintaining storage sufficient to meet a 7.5 maf
Lake Mead release requirement, while avoiding the likelihood of a future shortage
determination at a specified assurance level. Through a separate modeling study,
Reclamation determined the Lake Mead storage needed in each future year to meet
Lower Basin and Mexico demands, with a specified percent assurance that Lake Mead
would not drop below a specified elevation. Water stored in Lake Mead in excess of
that storage requirement is deemed surplus to be made available to theior
Lower Basin
Inter 17
states. The Shortage Protection Alternative used in this FEIS, commonly referred to as
0
f the
the 80P strategy, is described in more detail in Section. 2.3.6. r 29, 2
pt o
e

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ation on Nove
2.2.1.4 FLOOD CONTROL STRATEGY
jo N
Nava archived
in
cited 1686 surplus conditions are determined only when flood
Under a flood control strategy,4,
1 control releases from 4
No. Lake Mead are occurring or projected to occur in the subsequent
year. In the 1998, 1999 and 2000 Annual Operating Plans (AOPs), Reclamation used
the projection of flood control releases as the basis for making surplus water available
to the Lower Division States. The Flood Control Alternative in this FEIS uses this
strategy and is described in Section 2.3.3.
2.2.2

ORIGINS OF THE CALIFORNIA, SIX STATES, AND BASIN STATES
ALTERNATIVES

On December 17, 1997, California presented to the other Basin States its draft 4.4 Plan
(CRBC, 1997), a plan to achieve a reduction in its dependence on surplus water from
the Colorado River, through various conservation measures, water exchanges and
conjunctive use programs. One of the elements of the draft 4.4 Plan was the
expectation that the Secretary would continue to determine surplus conditions on the
Colorado River until 2015. California proposed criteria on which the Secretary would
base his determinations of surplus conditions during the interim period.
In 1998, in response to California’s 1997 proposal of interim surplus criteria, the other
six states within the Colorado River Basin (Six States) submitted a proposal with

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surplus criteria that were similar in structure to those in California’s proposal. Under the
proposal from the Six States, use of surplus water supplies would be limited depending
on the occurrence of various specified Lake Mead surface elevations. The interim
surplus criteria proposed by the Six States, presented in Attachment E, were used to
formulate the “Six States Alternative” presented in Section 2.3.4.
California subsequently proposed specific interim surplus criteria which were attached
to the October 15, 1999 Key Terms for Quantification Settlement Among the State of
California, Imperial Irrigation District, Coachella Valley Water District, and
Metropolitan Water District of Southern California (See Attachment F). California also
updated, renamed and re-released its 4.4 Plan in May 2000. The revised plan is now
known as the California Colorado River Water Use Plan (CA Plan). The interim
surplus criteria proposal stemming from the CA Plan and Quantification Settlement was
used to formulate the “California Alternative” detailed in Section 2.3.5.
In July 2000, during the public comment period on the DEIS, Reclamation received a
draft proposal for interim surplus criteria from the seven Colorado River Basin States
(Seven States). After a preliminary review of that proposal, Reclamation published it in
the August 8, 2000 Federal Register for review and consideration by the public during
the public review period for the DEIS. Reclamation published minorrior
corrections to the
Inte of 17 Federal
proposal in a Federal Register notice of September 22, 2000. e
Copies the
of th 29, 20
Register notices are in Chapter 5. Reclamation Dept. the Basin States Alternative in
derived
.
ber
this FEIS from the draft Seven States ation v
Proposal.
vem
o

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vajo hived on
a
2.2.3 PACIFIC ed in N
INSTITUTE,PROPOSAL
arc
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c
864
-16
On February 15,o. 14 a consortium of environmental organizations led by the Pacific
2000,
N

Institute for Studies in Development, Environment and Security (Pacific Institute)
presented an interim surplus criteria proposal for consideration by the Secretary. Their
proposal (as clarified by the Pacific Institute’s September 8, 2000 letter of comment on
the DEIS), contains interim surplus criteria that are similar to the criteria in the Six
States Alternative with respect to Lower Basin surplus determinations. The proposal
and excerpts from the September 8 letter are included as Attachment G to this FEIS.
The Pacific Institute Proposal also suggested that, during years when Lake Mead’s
surface elevation exceeds 1120.4 feet mean sea level (msl), at least 32,000 af of
additional water (i.e. water in excess of Mexico's treaty deliveries) be delivered to
Mexico for the purpose of restoring and/or maintaining habitat in the upper reaches of
the Colorado River delta. The proposal also included 260,000 af of additional water to
be delivered to the Colorado River delta for ecological restoration purposes when
reservoir elevations are high.
This proposal is beyond the purpose and need for the proposed action because it would
expand the proposed action by prescribing releases of Colorado River water stored in
Lake Mead to Mexico. The proposed adoption of surplus criteria for use in Arizona,
California and Nevada does not, by definition, apply to determinations of surplus to the

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United Mexican States (Mexico). Water delivery to Mexico is governed by the United
States-Mexico Water Treaty of 1944. Releases of water to Mexico are not addressed by
Section III(3) of the LROC or Article II(B)(2) of the Decree and are therefore not part
of the proposed action analyzed in this EIS. From its initiation of this proposed action
on May 18, 1999, Reclamation has clearly stated that its undertaking was intended to
“identify those circumstances under which the Secretary of the Interior (“Secretary”)
may make Colorado River water available for delivery to the States of Arizona,
California, and Nevada .…” (64 Federal Register 27008, May 18, 1999). The proposed
action only involves determinations of domestic surplus conditions pursuant to Article
III(3) of the LROC (64 Federal Register 27009). Section 1.1.4 of the DEIS (page 1-4)
states that “This proposed action is not intended to identify conditions when Mexico
may schedule [its] 0.2 maf [surplus under Article 10(b) of the Treaty].” The United
States, in its consultation with Mexico conducted through the Department of State, has
consistently informed Mexico that the proposed action does not address determinations
of surplus conditions to Mexico under the 1944 Treaty, and is limited to declarations of
surplus conditions for the Lower Division states.
In addition to changing and expanding the proposed action in a manner inconsistent
with the purpose and need for the action, the Pacific Institute’s proposed alternative
would also require that Reclamation make releases of water from Lakeor
nteri Mead to Mexico
in a manner that is inconsistent with the mandatory injunctione I
the
h issued to017Secretary by
ft
pt. o erCalifornia Decree
29, 2
the United States Supreme Court in Article II ofDe Arizona v.
. the
b
i for v Nov water
(1964). Pacific Institute’s proposal callson releases ofem from Lake Mead in
at
N
on
excess of the amount of water ajo would edreleased to Mexico “in satisfaction of [the
Navthatarchivbe
United States] obligations to 64,United States of Mexico under the treaty dated
ed in 8 the
cit.…” Reclamation does not believe that the range of reasonable
February 3, 1944 14-16
No.
alternatives includes alternatives that would violate the United States Supreme Court’s
Decree and injunction. For the foregoing reasons, Reclamation concluded that the
proposed alternative was not a reasonable alternative and it accordingly was not
analyzed in this EIS.
Because the Lower Basin surplus determinations of the Pacific Institute’s proposed
interim surplus criteria are similar to, and within the range of, those contained in the
alternatives already being analyzed, and because the proposed delivery of additional
water to Mexico is beyond the purpose and need for interim surplus criteria, the Pacific
Institute’s proposal is not analyzed in this FEIS.
2.2.4

FORMULATION OF ALTERNATIVES

In response to the CA Plan and the Six States proposal, and the dialogue among
Reclamation and the seven Basin States, Reclamation initiated a NEPA process to
provide structure to evaluating potential interim surplus criteria alternatives and to
determine and disclose the potential effects of these interim surplus criteria. At the
initiation of the NEPA process, Reclamation began a public scoping process. Under
that process, Reclamation conducted a series of public meetings in 1999 to inform

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interested parties of the consideration being given to the development of interim surplus
criteria, to show options and proposals developed up to that time, and to solicit public
and agency comments and suggestions regarding the formulation and evaluation of
alternatives for the criteria.
The alternatives below were presented at the public meetings:
Flood Control Alternative
Spill Avoidance Alternative (70R)
Flood Control Avoidance Alternative (70A)
Multi-tier Alternative (based on the Six States Plan)
Shortage Protection Alternative (80P)
The scoping process and issues identified, including those associated with alternatives
development, are discussed in Chapter 5 of this FEIS. Following the scoping meetings,
and in consideration of comments received, Reclamation included the interim surplus
criteria proposals of the Six States and California for evaluation in the DEIS. It should
be noted that while the California and Six States alternatives analyzed in the DEIS and
in this FEIS were based on criteria proposed by California and the Six States, the
respective alternatives presented in this FEIS do not contain all the specific elements of
ior
Inter 17
those plans.
the

20
of
ept. ber 29,
D
The draft Seven States proposal was discussed. informally with the public during the
m
ion v
atwas the n Nove comment in various letters
public review period for the DEIS, N
and
subject of
vajo h ved o
received by Reclamation Na
in in responsecto ithe DEIS and the Federal Register notice of the
, ar
c ond 1 discussions and comments, Reclamation formulated an
proposal. Basedite these 6864
alternative basedo. 14 Seven States proposal and identified it as the preferred
N on the

alternative (the Basin States Alternative herein). It should be noted that the Basin States
Alternative presented in this FEIS does not contain all the specific elements of the draft
Seven States proposal.
2.2.5

UTILIZATION OF PROPOSALS FROM THE BASIN STATES

As discussed in Section 2.2.2, various proposals submitted by individual Colorado
River Basin states or groups of states were used by Reclamation to formulate interim
surplus criteria alternatives. In recognition of the need to limit the delivery of surplus
water at lower Lake Mead water levels, these proposals specified allowable uses of
surplus water at various triggering levels.
The Secretary will continue to apportion surplus water consistent with the applicable
provisions of the Decree, under which surplus water is divided 50 percent to California,
46 percent to Arizona, and 4 percent to Nevada. The Secretary also intends to
appropriately report the accumulated volume of water delivered to MWD under surplus
conditions. The Secretary also intends to honor any forbearance arrangements made by

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various parties for the delivery of surplus water or reparations for future shortage
conditions.
2.2.6

NO ACTION ALTERNATIVE AND BASELINE CONDITION

As required by NEPA, a No Action alternative must be considered during the
environmental review process. Under the No Action Alternative, determinations of
surplus would continue to be made on an annual basis, in the AOP, pursuant to the
LROC and the Decree as discussed in Chapter 1. The No Action Alternative represents
the future AOP process without interim surplus criteria. Surplus determinations
consider such factors as end-of-year system storage, potential runoff conditions,
projected water demands of the Basin States and the Secretary’s discretion in addressing
year-to-year issues. However, the year-to-year variation in the conditions considered by
the Secretary in making surplus water determinations makes projections of surplus
water availability highly uncertain.
The approach used in this FEIS for analyzing the hydrologic aspects of the interim
surplus criteria alternatives was to use a computer model that simulates specific
operating parameters and constraints. In order to follow CEQ guidelines calling for a
No Action alternative for use as a “baseline” against which to compareor
i project
In er a baseline
alternatives, Reclamation selected a specific operating strategy fortuse as17
0
f the
condition, which could be described mathematically in the model. 9, 2
pt. o
e
r2

v. D v mbe
o
ation ostrategy.e Reclamation has utilized a 70R
The baseline is based on a 70Rajo N
avoidance N
v spill andived n surplus determinations in past years.
strategy for both planning purposesrch studies of
in Na
ited 6864, a surplus determinations as part of the DEIS effort,
c
When Reclamation reviewed previous
-1
the data indicated . 14the 1997 surplus determination did not precisely fit the 70R
o that
N
strategy. As a result, Reclamation selected the 75R strategy as representative of recent
operational decisions, for use as the baseline condition in the DEIS. However, based on
further review and analysis, public comment, and discussion with representatives of the
states during the DEIS review period, Reclamation is using the 70R strategy for the
baseline condition in this FEIS. While the 70R strategy is used to represent baseline
conditions, it does not represent a decision by Reclamation to utilize the 70R strategy
for determination of future surplus conditions in the absence of interim surplus criteria.
It should be noted that the 70R strategy and 75R strategy yield very similar results for
the purpose of determining impacts associated with the action alternatives analyzed in
this FEIS. Figure 2-1 illustrates the close relationship between the 70R and 75R trigger
lines (see Section 2.3.1.2).

2.3 DESCRIPTION OF ALTERNATIVES
This section describes the five interim surplus criteria alternatives analyzed in this
FEIS, and No Action, which is represented by the baseline condition for comparison
purposes. The Secretary would base his annual determination of surplus conditions on
the criteria selected, if any, as part of the AOP process unless extraordinary

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circumstances arise. Such circumstances could include operations necessary for safety
of dams or other emergency situations, the failure of California to meet its commitment
to reduce dependence on Colorado River water, or other activities arising from actual
operating experiences. The interim surplus criteria would remain in effect for surplus
determinations made through calendar year 2015, subject to five-year reviews
concurrent with the LROC reviews. As noted in Section 1.4.1, implementation of
interim surplus criteria would take into account the progress, or lack thereof, in the
implementation of the CA Plan.
As noted above, the 70R operating strategy is not presented as an alternative for
adoption. If an interim surplus criteria alternative is not implemented, the Secretary
would determine surplus conditions using the same dynamic considerations currently
used in the AOP.
Subsequent to the surplus determination for 2016, the interim surplus criteria would
terminate and, in the absence of subsequently-specified surplus criteria, surplus
determinations would be made by future Secretaries based on factors such as those that
are considered in the AOP, as discussed in Chapter 1.
Because the selected baseline and the interim surplus criteria alternatives deal with
ior
Inter 17
operations, rather than construction or other physical Colorado River system changes,
0
f the
the alternatives are described below in terms of their operatingrrules. 2 Department
pt. o e 29, The
e
D
mb
and Reclamation intend to deliver waterion v.
Article II(B)2 of the
at in accordance withto be available each year
Nove
N
n projected
o
o
Decree. The estimated volumesjof surplus water
ava
ved
under baseline conditionsN each rchi
in and 4, a alternative are tabulated to demonstrate the
cited 1686
operation under the respective conditions. The projected volumes of surplus water vary
4over the interim o. 1 in response to various factors including the implementation of
N period
various components of the CA Plan.
A common element of all alternatives is that in years in which the Field Working
Agreement between the Bureau of Reclamation and the Army Corps of Engineers for
Flood Control Operation of Hoover Dam and Lake Mead requires releases greater than
the downstream beneficial consumptive use demands, the Secretary shall determine a
“flood control surplus” will be declared in that year. In such years, releases will be
made to satisfy all beneficial uses within the United States (see the estimated amounts
under Flood Control for each alternative), and up to an additional 200,000 af will be
made available to Mexico under the Treaty.
2.3.1

NO ACTION ALTERNATIVE AND BASELINE CONDITION

2.3.1.1 APPROACH TO SURPLUS WATER DETERMINATION
As discussed above in Section 2.2.6, the 70R operating strategy is being used as a
baseline to show possible future operating conditions in the absence of interim surplus
criteria. The primary effect of simulating operation with the 70R operating strategy

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would be that surplus conditions would only be determined when Lake Mead is nearly
full.
2.3.1.2 70R BASELINE SURPLUS TRIGGERS
The 70R baseline strategy involves assuming a 70-percentile inflow into the system
subtracting out the consumptive uses and system losses and checking the results to see
if all of the water could be stored or if flood control releases would be required. If flood
control releases would be required, additional water is made available to the Lower
Basin states beyond 7.5 maf. The notation 70R refers to the specific inflow where 70
percent of the historical natural runoff is less than this value (17.4 maf) for the Colorado
River basin at Lee Ferry.
The 70R strategy is illustrated on Figure 2-1, which shows the average trigger elevation
of Lake Mead’s water surface above which a surplus would be determined. In practice,
the 70R surplus determination would not be based on the trigger line shown, but would
be made during the fall of the preceding year using projected available system space.
The 70R trigger line rises from approximately 1199 feet msl in 2002 to 1205 feet msl in
2050. The gradual rise of the 70R trigger line shown in Figure 2-1 is the result of
ior
Inter 1 a
increasing water use in the Upper Basin. Under baseline conditions, when7 surplus
the
0
condition is determined to occur, surplus water would .be f
pt o maderavailable to fill all water
29, 2
e
v D
orders by holders of surplus water contracts in.the Lowermbe
Division states in estimated
ation on Nove
N
amounts on Table 2-1.
ajo
d

ive
Nav
d in 64, arch
cite 168
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
2-8

1,000
2000

1,050

1,100

1,150

1,200

1,250

2005

2010

2015

2020

2-9

Year

2025

2030

2035

2040

M INIM UM NEVADA PUM PING ELEVATIO N=1000 FT

75R TRIGGER FOR COMPARISON

SPILLW AY ELEVATION=1221 FT

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in M64UMarc
cite 168 INIM , ELEVATION FO R POW ER GENERATION=1083 FT
o. 14
N

70R AVERAGE TRIGGER

AVERAGE FLOOD
RELEASE TRIGGER

Figure 2-1
Baseline Surplus Trigger Elevations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Lake Mead Elevation (feet)

DESCRIPTION OF ALTERNATIVES

2045

2050

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Table 2-1
Baseline Potential Surplus Water Supply
Unit : thousand acre-feet (kaf)
Year
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

2.3.2

Flood Control
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

70R Trigger
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

BASIN STATES ALTERNATIVE (PREFERRED ALTERNATIVE)

Reclamation has identified the Basin States Alternative as the preferred alternative in
rior
this FEIS. The Basin States Alternatives is similar to, and based nte information
I upon, 17
the the 20
submitted to the Secretary by representatives of the pt. of
governors of29, states of Colorado,
e
r
Wyoming, Utah, New Mexico, Arizona,ion v. D California. After receipt of this
Nevada and vembe
t
No
information (during the public ajo Na period), Reclamation shared the submission
v commentved on Reclamation’s surplus criteria web
with the public (through the Federalchi
in Na
r Register and
ited and 864, a Reclamation then analyzed the states’
c
sites) for consideration 16 comment.
14submission and crafted this additional alternative for inclusion in the FEIS. Some of the
No.
information submitted for the Department’s review was outside of the scope of the
proposed action for adoption of interim surplus criteria and was therefore not included
as part of the Basin States Alternative (i.e., adoption of shortage criteria and adoption of
surplus criteria beyond the 15-year period) as presented in this FEIS. With respect to
the information within the scope of the proposed action, Reclamation found the Basin
States Alternative to be a reasonable alternative and fully analyzed all environmental
effects of this alternative in this FEIS. The identified environmental effects of the Basin
States Alternative are well within the range of anticipated effects of the alternatives
presented in the DEIS and do not affect the environment in a manner not already
considered in the DEIS.
Reclamation selected the Basin States Alternative as its preferred alternative based on
Reclamation's determination that it best meets all aspects of the purpose and need for
the action, including the needs to remain in place for the entire period of the interim
criteria, to garner support among the Basin States that will enhance the Secretary’s
ability to manage the Colorado River reservoirs in a manner that balances all existing
needs for these precious water supplies, and to assist in the Secretary’s efforts to insure
that California water users reduce their over reliance on surplus Colorado River water.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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DESCRIPTION OF ALTERNATIVES

CHAPTER 2

Reclamation notes the important role of the Basin States in the statutory framework for
administration of Colorado River Basin entitlements and the significance that a sevenstate consensus represents on this issue. Thus, based on all available information, this
alternative appears to be the most reasonable and feasible alternative.
2.3.2.1 APPROACH TO SURPLUS WATER DETERMINATION
The Basin States Alternative specifies ranges of Lake Mead water surface elevations to
be used through 2015 for determining the availability of surplus water through 2016.
The elevation ranges are coupled with specific uses of surplus water in such a way that,
if Lake Mead’s surface elevation were to decline, the amount of surplus water would be
reduced. The interim criteria would be reviewed at five-year intervals with the LROC
(and additionally as needed) and revised as needed based upon actual operational
experience.
2.3.2.2 BASIN STATES ALTERNATIVE SURPLUS TRIGGERS
The surplus determination elevations under the preferred alternative consist of the tiered
Lake Mead water surface elevations listed below, each of which is associated with
certain stipulations on the purposes for which surplus water could be used. The
rior
elevation tiers (also referred to as levels) are shown on Figuree Inte
2-2. They are as follows,
017
f th
proceeding from higher to lower water levels:
pt. o
29, 2
e

.D
ber
v feet
ion v to 1201 em msl)
Nat
Tier 1 - 70R Line (approximately 1199 n No
vajo hived o
Tier 2 - 1145 feet Na
in msl
rc
itedfeet 6864, a
Tier 3 -c
1125
msl
-1
o. 14
N

Table 2-2 lists the estimated maximum annual amounts of surplus water that would be
available to contractors for surplus water in the Lower Division states under the Basin
States Alternative, when Lake Mead is at or above each trigger. The table also lists the
estimated amounts of surplus water that would be available to the Lower Division states
when flood control releases are required.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
2-11

2000

1,000

1,050

1,100

1,150

1,200

1,250

70R AVERAGE TRIGGER

SPILLW AY ELEVATION=1221 FT

2005

2010

2015

2020

2-12

Year

2025

2030

2035

M INIM UM NEVADA PUM PING ELEVATIO N=1000 FT

2040

ior
Inter 17
TIER 2=1145
e
of th 29, 20
pt.
TIER 3=1125
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64,Marc ELEVATION FO R POW ER GENERATION=1083 FT
INIM UM
cite 168
14
No.

TIER 1=(70R)

AVERAGE FLOOD
RELEASE TRIGGER

Figure 2-2
Basin States Alternative Surplus Trigger Elevations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Lake Mead Elevation (feet)

DESCRIPTION OF ALTERNATIVES

2045

2050

CHAPTER 2

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DESCRIPTION OF ALTERNATIVES

CHAPTER 2

Table 2-2
Basin States Alternative Potential Surplus Water Supply
Unit: thousand acre-feet (kaf)
Year
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

Flood
Control
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

Tier 1
(70R)
1150
1150
1050
1050
1050
1050
1100
1100
1150
1150
1200
1200
1200
1200
1200

Tier 2
(1145 feet)
650
600
550
550
500
500
450
450
450
450
450
450
450
450
450

Tier 3
(1125 feet)
200
200
150
150
150
150
150
150
150
200
200
250
250
300
300

The surplus amounts quantified for each tier in Table 2-2 are estimated annual
ior
quantities of water and are the Secretary’s best estimate of the amounts of surplus water
Inter 17
th interim surplus guidelines.
that could be made available during the 15-year period offthe e
0
pt. o er 29, 2 projected
e
These estimates are based on the most current .available data regarding
v D
mb
Colorado River water use demands Naexisting contractors. The methodology that was
by tion n Nove
o that d o
used to prepare the demandavaj
scheduleshiveunderlie the surplus tables in this section is
c
in Nof “domestic,” “Direct Delivery Domestic Use” and “Offbased upon thecited
definitions 864, ar
6
Stream Banking,” .as used in the information submitted to the Secretary by the Colorado
14-1
o (65 Federal Register 48531, 48535 [Aug. 8, 2000]). The quantities
N
River Basin states
in each Tier are developed by using these definitions as set forth in the Basin States
submission (see Table 2-2). Under these definitions, the quantity of estimated surplus
quantities is based, in part, on supplying particular types of uses within the Lower
Division states, with a higher priority for supplying domestic uses than that for
irrigation uses or groundwater banking activities to supply future uses.
While the Secretary, as an initial matter, would make surplus water available in
amounts consistent with the percentages identified in Article II(B)(2) of the Decree, it is
expected that water orders from Colorado River contractors will be submitted to reflect
forbearance arrangements made by Lower Division states and individual contractors.
The Secretary will deliver water to contractors in a manner consistent with these
arrangements, to the extent that the water orders from contractors reflect these
arrangements. The Secretary expects to make the specified quantities of water available
during the 15-year period. However, the precise annual surplus quantities will continue
to be reviewed on an annual basis during the preparation of the AOP, as required by
applicable federal law, based on actual operating experience and updated information
on the demand for Colorado River water by Lower Division contractors.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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DESCRIPTION OF ALTERNATIVES

2.3.2.1.1

CHAPTER 2

Basin States Alternative Tier 1 (70R)

The Basin States Alternative Tier 1 Lake Mead surplus trigger elevations are based on
the 70R strategy and range from approximately 1199 feet msl to 1201 feet msl. In years
when the Secretary determines that water should be released for beneficial consumptive
use to reduce the risk of potential flood control releases based on the 70R operating
strategy, the Secretary would determine the quantity of surplus water available and
allocate it as follows: 50 percent to California, 46 percent to Arizona and 4 percent to
Nevada.
Regardless of the quantity of surplus water determined under Tier 1, surplus deliveries
under Tier 2 (discussed below) would be met.
2.3.2.1.2

Basin States Alternative Tier 2 (1145 feet msl)

The Basin States Alternative Tier 2 Lake Mead surplus trigger elevation is 1145 feet
msl. At or above this Tier 2 elevation (and below the Tier 1 elevation), surplus water
would be available for use by the Lower Division states in the estimated amounts in
Table 2-2.

ior
Inter 17
f the 9, 20
pt. o erelevation is 1125 feet
2
The Basin States Alternative Tier 3 Lake Mead De
trigger
n v. surplus emb
msl. At or above this Tier 3 elevation (and below Nov 2 elevation), surplus water
the Tier
Natio
ajoLowerved on states in the estimated amounts on
vthe
would be available forin Nby
use a
rchi Division
ite Mead6864,below the Tier 3 trigger surplus water would not be
Table 2-2. At Laked
levels a
c
made available. o. 14-1
N
2.3.2.1.3

Basin States Alternative Tier 3 (1125 feet msl)

2.3.2.2 DRAFT GUIDELINES
Draft guidelines for implementation of the Basin States Alternative are presented in
Attachment I. These guidelines describe in more detail the relationships between the
implementation of interim surplus criteria under this alternative and the AOP process
through which the Secretary would determine whether surplus water is available and
how much is available.
2.3.3 FLOOD CONTROL ALTERNATIVE
2.3.3.1 APPROACH TO SURPLUS WATER DETERMINATION
Under the Flood Control Alternative, a surplus condition is determined to exist when
flood control releases from Lake Mead are occurring or projected to occur in the
subsequent year. The method of determining need for flood control releases is based on
flood control regulations published by the Los Angeles District of the Corps and the
Field Working Agreement between the Corps and Reclamation, which are discussed in
Section 1.3.6, Flood Control Operation.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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DESCRIPTION OF ALTERNATIVES

CHAPTER 2

2.3.3.2 FLOOD CONTROL ALTERNATIVE SURPLUS TRIGGERS
Under the flood control strategy, a surplus is determined when the Corps flood control
regulations require releases from Lake Mead in excess of downstream demand. The
specific operating provisions are described in Section 1.3.6, Flood Control Operation.
If flood control releases are required, surplus conditions are determined to be in effect.
This strategy is illustrated on Figure 2-3, which shows the average Lake Mead water
surface elevation that would trigger flood control releases. The average triggering
elevation is a level line at approximately 1211 feet msl. In practice, flood control
releases are not based on the average trigger line shown, but would be determined each
month by following the Corps regulations. The graph is a visual representation to
illustrate the differences between the alternatives. When a flood control surplus is
determined, surplus water would be made available for all established uses by
contractors for surplus water in the Lower Division states. Table 2-3 lists the annual
amounts of surplus water estimated to be available under the Flood Control Alternative.
Table 2-3
Flood Control Alternative
Potential Surplus Water Supply
Unit: thousand acre-feet (kaf)

ior
Inter 17
Year
0
f the
pt. o er 29, 2
e
2002
.D
mb
2003 tion v
a
Nove
N
on
jo2004
2005
Nava archived
in
cited 16864, 2006
2007
2008
o. 14
N
2009
Flood
Control
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

2010
2011
2012
2013
2014
2015
2016

2.3.4

SIX STATES ALTERNATIVE

2.3.4.1 APPROACH TO SURPLUS WATER DETERMINATION
The Six States Alternative specifies ranges of Lake Mead water surface elevations to be
used through 2015 for determining the availability of surplus water through 2016. The
elevation ranges are coupled with specific uses of surplus water in such a way that, if
Lake Mead’s surface elevation were to decline, the amount of surplus water would be
reduced. The interim criteria would be reviewed at five-year intervals with the LROC
and as needed based upon actual operational experience.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
2-15

1,000
2000

1,050

1,100

1,150

1,200

1,250

2005

2010

2015

2020

2-16

Year

2025

2030

2035

M INIM UM NEVADA PUM PING ELEVATIO N=1000 FT
2040

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168 M INIM UM ELEVATION FO R POW ER GENERATION=1083 FT
o. 14
N

AVERAGE FLOOD
RELEASE TRIGGER

SPILLW AY ELEVATION=1221 FT

Figure 2-3
Flood Control Alternative Surplus Trigger Elevations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Lake Mead Elevation (feet)

DESCRIPTION OF ALTERNATIVES

2045

2050

CHAPTER 2

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7 0 R A V E R A G E T R IG G E R

SPILLW AY ELEVATION=1221 FT

2005

T IE R 2 = 1 1 4 5

2010

2015

2020

2-17

Year

2025

2030

2035

2040

ior
Inter 17
e
of th 29, 20
pt.
T IE R 3 = 1 1 2 5
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64,Marc ELEVATION FO R POW ER GENERATION=1083 FT
INIM UM
cite 168
41
No.

T IE R 1 = ( 7 0 R )

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

2000

1,000

1,050

1,100

1,150

1,200

AVERAGE FLOOD
RELEASE TRIGGER

Figure 2-4
Six States Alternative Surplus Trigger Elevations

M

1,250

DESCRIPTION OF ALTERNATIVES

2045

2050

CHAPTER 2

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DESCRIPTION OF ALTERNATIVES

CHAPTER 2

2.3.4.2 SIX STATES ALTERNATIVE SURPLUS TRIGGERS
The surplus determination elevations under the Six States Alternative consist of the
tiered Lake Mead water surface elevations listed below, each of which is associated
with certain stipulations on the purposes for which surplus water could be used. The
tiered elevations are shown on Figure 2-4. They are as follows, proceeding from higher
to lower water levels:
Tier 1 - 70R Line (approximately 1199 to 1201 feet msl)
Tier 2 - 1145 feet msl
Tier 3 - 1125 feet msl
The following sections describe the various tiers and the estimated amounts of surplus
water available at those tiers under the Six States Alternative. When flood control
releases are made, any and all beneficial uses would be met, including unlimited
off-stream storage.
2.3.4.2.1

Six States Alternative Tier 1 (70R)

Six States Alternative Tier 1 Lake Mead surplus trigger elevations areior
er based on the 70R
strategy and range from approximately 1199 feet msl to 1201 e Inmsl during the
feet t
017
f th
interim period. When Lake Mead surface elevations t. oat or above, the 70R line (and
pare
29 2
. De
ber
below the average flood release trigger tline shown in Figure 2.4), surplus water would
ion v Novem
Na
be available. Table 2-4 lists the jestimateded on amounts of surplus water that would
va o hiv annual
a
be available to the LowerN
in Division states under the Basin States Alternative, when Lake
rc
ited Tier 1 4, a The table also lists the estimated amounts of
c the 1686 trigger.
Mead is at or above 14
surplus water that .would be available to the Lower Division states when flood control
No
releases are required.
Table 2-4
Six States Alternative Potential Surplus Water Supply
Unit: thousand acre-feet (kaf)
Year
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

Flood
Control
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

Tier 1

Tier 2

Tier 3

1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

600
550
500
500
450
450
450
400
400
400
400
400
400
400
400

350
300
250
250
200
200
150
150
150
150
150
150
150
150
150

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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DESCRIPTION OF ALTERNATIVES

2.3.4.2.2

CHAPTER 2

Six States Alternative Tier 2 (1145 feet msl)

The Six States Alternative Tier 2 Lake Mead surplus trigger elevation is 1145 feet msl.
At or above this Tier 2 elevation (and below the Tier 1 elevation), surplus water would
be available for use by the Lower Division states in the estimated amounts on Table 2-4.
2.3.4.2.3

Six States Alternative Tier 3

The Six States Alternative Tier 3 Lake Mead surplus trigger elevation is 1125 feet msl.
At or above this Tier 3 elevation (and below the Tier 2 elevation). Surplus water would
be available for use by the Lower Division states in the estimated amounts on Table 2-4.
When Lake Mead water levels are below the Tier 3 trigger elevation, surplus water
would not be available.
2.3.5

CALIFORNIA ALTERNATIVE

2.3.5.1 APPROACH TO SURPLUS WATER DETERMINATION
The California Alternative specifies Lake Mead water surface elevations to be used for
or
the interim period through 2015 for determining the availability Ioftsurplus water
n eri 7
through 2016. The elevation ranges are coupled with specifice
surplus
f th uses of201 water in
pt. o theramount of surplus water
29,
e
such a way that, if Lake Mead’s surface elevation declines, be
v. D
m
would be reduced.
ation n Nove
N

vajo hived o
in Na 4, arcURPLUS TRIGGERS
2.3.5.2 CALIFORNIA ALTERNATIVE S
cited 1686
. 14Nelevations at which surplus conditions would be determined under the
The Lake Mead o

California Alternative are indicated by a series of tiered, sloping lines from the present
to 2016. Each tiered line would be coupled with limitations on the amount of surplus
water available at that tier. Figure 2-5 shows the structure of these tiered lines. Each
tier is defined as a trigger line that rises gradually year by year to 2016, in recognition
of the gradually increasing water demand of the Upper Division states. The elevations
associated with the three tiers are as follows:
Tier 1 - 1160 feet msl to 1166 feet msl
Tier 2 - 1116 feet msl to 1125 feet msl
Tier 3 - 1098 feet msl to 1102 feet msl
Each tier under the California Alternative would be subject to adjustment during the
interim period based on changes in Upper Basin demand projections or other factors
during the five-year reviews or as a result of actual operating experience. The
following sections describe the California Alternative tiers. When flood control
releases are made, any and all beneficial uses would be met, including unlimited offstream storage.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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DESCRIPTION OF ALTERNATIVES

2.3.5.2.1

CHAPTER 2

California Alternative Tier 1

California Alternative Tier 1 Lake Mead surplus trigger elevation increases from an
initial elevation of 1160 feet msl to 1166 feet msl at the end of the interim period (based
on Upper Basin demand projections). Lake Mead water surface elevations at or above
the Tier 1 trigger line would permit surplus water deliveries to the Lower Division
states in the estimated amounts on Table 2-5. The table also lists the estimated amounts
of surplus water that would be available to the Lower Division states when flood control
releases are required.
Table 2-5
California Alternative Potential Surplus Water Supply
Unit: thousand acre-feet (kaf)
Year
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

Flood
Control
1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

Tier 1

Tier 2

Tier 3

1350
1350
1350
1350
1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

650
600
550
550
500
450
450
450
400
400
400
400
400
400
400

550
500
400
400
400
350
350
350
300
300
300
300
300
300
300

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

2.3.5.2.2 California Alternative Tier 2
California Alternative Tier 2 Lake Mead surplus trigger elevation increases from
1116 feet msl to 1125 feet msl (based on Upper Basin demand projections). Lake Mead
water surface elevations at or above the Tier 2 line (and below the Tier 1 line) would
permit surplus water diversions for use by the Lower Division states in the estimated
amounts on Table 2-5.
2.3.5.2.3

California Alternative Tier 3

California Alternative Tier 3 trigger elevation increases from 1098 feet msl to 1102 feet
msl (based on Upper Basin demand projections). Lake Mead water surface elevations
at or above the Tier 3 line (and below the Tier 2 line) would permit surplus water
diversions for use by the Lower Division states in the estimated amounts on Table 2-5.
When Lake Mead water levels are below the Tier 3 trigger elevation, surplus water
would not be made available.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
2-20

1,000
2000

1,050

1,100

1,150

1,200

1,250

2005

2010

2015

2020

2-21

2025
Year

2030

2035

M INIM UM NEVADA PUM PING ELEVATIO N=1000 FT
2040

CALIFO RNIA'S TIER 3 RECOM M ENDATION (FOR COM PARISO N)

70R AVERAGE TRIGGER

SPILLW AY ELEVATION=1221 FT

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
TIER 2=1116 TO 1125
ation on Nov
N
vajo hived
Na
TIER 3=1098 TO 1102
d in 64, arc
cite 168
M INIM UM ELEVATION FO R POW ER GENERATION=1083 FT
o. 14
N

TIER 1=1160 TO 1166

AVERAGE FLOOD
RELEASE TRIGGER

Figure 2-5
California Alternative Surplus Trigger Elevations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Lake Mead Elevation (f

DESCRIPTION OF ALTERNATIVES

2045

2050

CHAPTER 2

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DESCRIPTION OF ALTERNATIVES

2.3.6

CHAPTER 2

SHORTAGE PROTECTION ALTERNATIVE

2.3.6.1 APPROACH TO SURPLUS WATER DETERMINATION
The Shortage Protection Alternative is based on maintaining an amount of water in
Lake Mead necessary to provide a normal annual supply of 7.5 maf for the Lower
Division, 1.5 maf for Mexico and storage necessary to provide an 80 percent probability
of avoiding future shortages. The modeling assumptions for shortage protection are
discussed in Section 3.3.3.4, Lake Mead Water Level Protection Assumptions.
2.3.6.2 SURPLUS TRIGGERS
The surplus triggers under this alternative range from an approximate Lake Mead initial
elevation of 1126 feet msl to an elevation of 1155 feet msl at the end of the interim
period, as shown on Figure 2-6. At Lake Mead elevations above the surplus trigger,
surplus conditions would be determined to be in effect and surplus water would be
available for use in the Lower Division states in the estimated amounts on Table 2-6.
Below the trigger elevation, surplus water would not be made available.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ationControlNoveSurplus
Year jo N Flood on
Amount
Nava archived
1350
1350
d in 20024,
cite 1686
2003
1350
1350
1350
1350
. 14- 2004
No
2005
1350
1350
Table 2-6
Shortage Protection Alternative
Potential Surplus Water Supply
Unit: thousand acre-feet (kaf)

2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

2.4

1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

1400
1450
1500
1550
1600
1600
1650
1650
1650
1700
1700

SUMMARY TABLE OF IMPACTS

Table 2-7 presents a summary of the potential effects of the baseline operation and the
interim surplus alternatives. Chapter 3 contains detailed descriptions of these effects.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
2-22

1,000
2000

1,050

1,100

1,150

1,200

1,250

2005

2010

2015

2020

2-23

2025
Year

2030

2035

M INIM UM NEVADA PUM PING ELEVATIO N=1000 FT

70R AVERAGE TRIGGER

SPILLW AY ELEVATION=1221 FT

2040

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168 M IN IM U M ELEV A TIO N FO R PO W ER G EN ERA TIO N =1083 FT
o. 14
N

SHORTAGE PROTECTION
ALTERNATIVE

AVERAGE FLOOD
RELEASE TRIGGER

Figure 2-6
Shortage Protection Alternative Trigger Elevations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Lake Mead Elevation (feet)

DESCRIPTION OF ALTERNATIVES

2045

2050

CHAPTER 2

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After 2016, median levels stabilize, then rise
and fall slightly, due to 602(a) storage
requirements and less frequent equalization
releases.

The probability of Lake Powell being full in
2016 is 27%.

3

Reservoir water levels exhibit a gradual
declining trend during the interim surplus criteria
period as a result of increasing Upper Division
states consumptive use. The median water
surface elevation in 2016 is 3665 feet msl.

Baseline Conditions/No Action

2

3664 feet msl
3665 feet msl
3664 feet msl
3660 feet msl
3659 feet msl

After 2016, Lake Powell water levels under all five alternatives
tend to stabilize similar to baseline conditions. Water levels
under the Basin States, Flood Control, Six States, California
and Shortage Protection alternatives tend to converge with the
baseline conditions by about year 2030.

Basin States
Flood Control
Six States
California
Shortage Protection

Median Elevations in 2016 for each of the alternatives are as
follows:

Effects of Alternatives

Table 2-7
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

CHAPTER 2

2-24

Flows downstream of Hoover Dam are
governed by downstream demand or Hoover
Dam flood control releases.

Flows downstream of Glen Canyon Dam would
be managed in accordance with the 1995 Glen
Canyon Dam EIS and the 1996 ROD.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Glen Canyon and Hoover Dam
releases and flows downstream of
Lake Mead.

River Flows

Other alternatives: Flows below Glen Canyon Dam would be
similar to baseline conditions. Flows from Hoover Dam to
Parker Dam would be moderately higher until 2016 because of
surplus deliveries. After 2016, flows would be similar to
baseline conditions.

baseline conditions.
Flood Control Alternative: Similar to baseline conditions.

ior
Inter 17
e
of th 29, 20
Median Elevations in 2016 for each of the alternatives are as
Lake Mead Water Surface
Reservoir water levels exhibit a gradual
pt.
Elevations
declining trend during the interim surplus criteria follows: er
. De emb
v
period as a result of Lower Basin consumptive
Potential changes in Lake Mead water
1143 feet msl
ation on N v Basin States
use exceeding long-term inflow. The median o
surface elevations.
Flood Control
1162 feet msl
water surface elevation in 2016 isd
ajo N ive 1162 feet
v
Six States
1146 feet msl
msl. Na
ch
in
California
1131 feet msl
d After 2016,64, ar surface elevations
cite continue8 median water at a lower rate,
Shortage Protection
1130 feet msl
decline,
4-16 to frequent although surplus
1
Lower Basin
After 2016, median surface elevations continue to decline. By
No. due to less
deliveries.
about 2035, all alternatives converge to elevations similar to

Potential changes in Lake Powell
water surface elevations.

Lake Powell Water Surface
Elevations

Reservoirs Elevations and River Flows

Resource/Issue

DESCRIPTION OF ALTERNATIVES

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2002 through 2016
2017 through 2050

2002 through 2016
2017 through 2050
2002 through 2016
2017 through 2050

Surplus:
Shortage:
Normal:
Surplus:

2002 through 2016
2017 through 2050

Normal:

>96%
50%

0%
0%

47%
21%

100%
100%

Baseline Conditions/No Action

2

Other Alternatives: Greater probability of surplus through 2016
under the California and Shortage Protection alternatives and
slightly lower (26%) under the Basin States and Six States
alternatives. The probability of surplus under the alternatives is
about the same as baseline from 2017 to 2050. The probability
of shortage condition deliveries under the alternatives is slightly
higher (7% to 14%) through 2016. From 2017 to 2050, the
probability of shortages under the alternatives is similar to
baseline conditions.

Flood Control Alternative: Similar to baseline conditions.

Other Alternatives: Greater probability of surplus through 2016.
The probability is similar to baseline conditions from 2017
through 2050. Deliveries less than the normal apportionment
(4.4 mafy) do not occur under the alternatives at any time
through 2050.

Flood Control Alternative: Similar to baseline conditions.

Effects of Alternatives

Table 2-7
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

CHAPTER 2

100%
100%

2002 through 2016
2017 through 2050
2002 through 2016
2016 through 2050
2002 through 2016
2017 through 2050

Normal:
Surplus:
Shortage:

2-25

0%
0%

26%
19%

< 4%
50%

29%
21%

Shortage: 2002 through 2016
2017 through 2050

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Probabilities of meeting Treaty delivery
obligations.

Mexico Treaty Delivery

4

2002 through 2016
2017 through 2050

The Flood Control Alternative would provide slightly higher (1%)
probabilities of surplus than under baseline conditions through
2016. The rest of the alternatives provide slightly lower (3% to
7%) probabilities of surplus through 2016 and about the same
level as baseline through 2050. Deliveries less than the treaty
apportionment (1.5 mafy) do not occur under the alternatives at
any time through 2050.

the alternatives through 2016. From 2017 to 2050, the
probability of shortage condition deliveries is higher (3% to 5%)
under the alternatives.

ior
Inter 17
e
of th 29, 20
Shortage: 2002 through 2016
< 4%
t.
2017 through 2050
D p
.50%e ember
v
ation on Nov
N
vajo hived
n Na 2002 arc
d iNormal: 64, through 2016
96%
Nevada Water Supply
Flood Control Alternative: Similar to baseline conditions.
cite 168 2017 through 2050
50%
Probabilities of normal, surplus and
Other Alternatives: Greater probability of surplus through 2015;
shortage conditions.
same as baseline from 2017 to 2050. The probability of
o. 14
Surplus:
2002 through 2016
47%
N
shortage condition deliveries is slightly higher (7% to 14%) for
2017 through 2050
21%

Probabilities of normal, surplus and
4
shortage conditions.

Arizona Water Supply

Probabilities of normal, surplus and
4
shortage conditions.

California Water Supply

Water Supply

Resource/Issue

DESCRIPTION OF ALTERNATIVES

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2

Modeling indicates potential for slight reductions in salinity
under each alternative as compared to baseline.

Effects of Alternatives

Increased potential for lower Lake Mead levels
and increased inflow channel lengths under
baseline projections could increase potential of
elevated contaminant concentrations.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential effects on Lake Mead and
Lake Powell fisheries and associated
aquatic habitat.

Lake Habitat and Sport Fisheries

2-26

Species are adapted to fluctuating reservoir
levels. Therefore, increased potential for lower
Lake Mead and Lake Powell surface levels is
not expected to adversely affect aquatic
species.

Compared with baseline conditions, slightly increased potential
for higher reservoir levels under the Flood Control Alternative
and increased potential for lower reservoir levels under the
other alternatives would not be expected to result in substantial
changes to lake habitat.

Davis and Parker Dams.

Aquatic Resources

under baseline conditions.

Parker Dam
10%
Average annual probability from 2017 through
2050:
Davis Dam
5%
Parker Dam
6%

Beach/Habitat-Building Flow
Releases

ior
Inter 17
e
Probability of BHBF release conditions
of th 29, 20
from Glen Canyon Dam.
pt.
. De ember
ion v N v
Low Steady Summer Flows
The average annual Nat
probability of conditions o The probability under the alternatives is typically less than
on
requisite for lowjsteady summer flows is 38%
under baseline conditions during the first seven years and
Probability of requisite conditions for
v o
e through
through a and 62% from v
similar to or slightly greater than under baseline conditions
N2016a archi 2017d
low steady summer flow releases from
in
thereafter.
d 2050. 64,
Glen Canyon Dam.
cite 168
Flooding Downstream of Hoover
Average annual probability from 2002 through
The probability under the Flood Control Alternative is slightly
Dam
2016:
greater than under baseline conditions.
o. 14
N
Davis Dam
9%
Probability of damaging flows below
The probability under other alternatives is slightly less than
The probability under the alternatives is typically less than
under baseline conditions during the interim period, and
converges with baseline conditions thereafter.

The alternatives, except the Flood Control Alternative, result in
slightly increased potential for increased contaminant
concentrations in Boulder Basin, due to greater potential for
lower Lake Mead levels than under baseline conditions.

Baseline projections assume compliance with
numeric criteria along the river. The Basin
States are committed to meeting the numeric
criteria.

Baseline Conditions/No Action

Table 2-7
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

CHAPTER 2

The average annual probability of BHBF
releases is 16% through 2016 and 14% from
2017 through 2050.

Flow-Related Issues

Contaminant concentrations in Boulder
Basin of Lake Mead, in proximity to the
SNWS intakes at Saddle Island.

Lake Mead Water Quality and Las
Vegas Water Supply

Potential change in salinity below
Hoover Dam.

Colorado River Salinity

Water Quality

Resource/Issue

DESCRIPTION OF ALTERNATIVES

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2

Although reservoir elevations would differ, the effects of all
alternatives would be similar to baseline conditions.

Effects of Alternatives

The Flood Control Alternative would have slightly lower
potential, while the other alternatives would have increased
potential, for lower reservoir elevations and associated potential
increases in delta habitat.

Under baseline conditions, special-status plant
species would continue to be affected by
fluctuating water levels, which would
periodically expose and inundate areas where
the plants occur.

Baseline Conditions/No Action

Table 2-7
1
Summary of Potential Effects of Implementing Interim Surplus Criteria

CHAPTER 2

Under baseline conditions, increased potential
over time for lower reservoir levels could
increase potential for development of temporary
riparian habitat at the deltas, which would
benefit special-status wildlife species that utilize
such habitat.

The Flood Control Alternative has slightly lower potential, and
each of the other alternatives have higher potential, for each of
navigation hazards and reduced carrying capacity.

Boaters may have reduced take-out
opportunities due to increased potential for
lower reservoir surface elevations.

2-27

The Flood Control Alternative has lower potential, and each of
the other alternatives have increased potential, for reduced
take-out opportunities resulting from lower reservoir elevations.

Baseline condition projections indicate an
increased potential for the occurrence of lower
Lake Mead and Lake Powell reservoir levels,
which may result in potential increases in
navigation hazards and decreased safe boating
capacity (due to decreased reservoir surface
area).

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential effects on river boating at
Lake Powell and Lake Mead inflow
areas.

River and Whitewater Boating

Potential effects on reservoir boating
that may result from changes in Lake
Mead and Lake Powell surface
elevations.

Reservoir Boating/Navigation

facilities to accommodate lower surface
elevations.

rior
Intefor lower reservoir levels under the various
Special-Status Fish
Under baseline conditions, increased potential
Changes in potential
e
for lower elevations is not expected to have
alternatives would not change potential for effects.
of th 29, 2017
Potential effects of Lake Mead and
.
effects on special-status species fish different pt
Lake Powell reservoir level changes
. De ember
than those that occur at present. v
on special-status fish species.
n
Natio d on Nov
Recreation
vajo
Reservoir Marinas/Boat Launching
Baseline condition projections indicate
Flood Control
a
decreased
Napotentialarchivelevels lower Thelower reservoir Alternative hastheslightly alternativespotential
in
for
levels; each of
other
have
d increased 64, for reservoir normal
Potential effects on shoreline
t
ciine than those considered within the
increased potential for lower levels and necessary relocations.
recreation facilities from changes
-168
operating range that some existing facilities
Lake Mead and Lake Powell surface 14
to accommodate.
elevations.
No. may be ablewould likely result inSuch
occurrence
modification of

Potential effects on special-status
wildlife species associated primarily
with potential effects on riparian
habitat at the Lake Mead and Virgin
River deltas, and the lower Grand
Canyon.

Special-Status Wildlife

Potential effects on special-status
plants for areas influenced by Lake
Powell and Lake Mead water levels.

Special-Status Plants

Special-Status Species

Resource/Issue

DESCRIPTION OF ALTERNATIVES

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The Flood Control Alternative is similar to baseline conditions.

The Flood Control Alternative is similar to baseline conditions.
Other alternatives have greater potential for increased
relocation costs, based on an average cost per foot associated
with relocating facilities.

Baseline condition projections indicate
increased relocation costs associated with
future increased potential for lower reservoir
levels.

Glen Canyon Powerplant average annual
energy production:

Changes in reservoir elevations under each of the alternatives
would not be expected to adversely affect sport fisheries or
fishing in either reservoir.

Potential effects on sport fisheries are minimal
under baseline conditions.

CHAPTER 2

2-28

4532 GWh through 2016; 4086 GWh from 2017
through 2050.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Potential for changes in energy
production at Glen Canyon and
Hoover powerplants.

California
Shortage Protection

$544,843
$532,635

Average annual power production under the other alternatives
is greater than under baseline conditions for the first six to eight
years, then is less for the remaining years. Averaged from
2002 to 2050, Glen Canyon annual power production is from 12
to 30 GWh less than baseline conditions, while Hoover power
production is from 51 to 127 GWh less.

ior
Inter 17
e
Hoover Powerplant average annual energy
of th 29, 20
production:
ept.
. D2017 ember
vfrom
4685 GWh through 2016; 3903 n
atio GWh on Nov
through 2050.
jo N ve water
vaverage Lake iMeadd levels The increase over baseline conditions of annual pumping costs
Pumping Power Needs for SNWS
Future lower a
for each alternative follows:
in Na 4, arch
Potential change in the cost of power d would require more energy and increased
costs
cite pumping86 for the SNWS intake.
to pump Lake Mead water through the
6
Basin States
$229,395
SNWS.
14-1
Flood Control
$ 32,685
o.
N
Six States
$214,779

Hydroelectric Power Production

Energy Resources

Increased costs associated with
relocating shoreline facilities to remain
in operation at lower reservoir
elevations.

Recreation Facilities Relocation
Costs

Potential effects on sport fishing in
Lake Mead and Lake Powell.

Reservoir Sport Fishing

DESCRIPTION OF ALTERNATIVES

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Increased potential for lower reservoir levels
would increase potential for shoreline exposure
under baseline conditions. Increases in fugitive
dust emissions would be minimal due to low
emission potential of shoreline.

Future lower average Lake Powell water levels
would require more energy and increased
pumping costs for the Navajo Generating
Station and the City of Page.

$ 529
$
0
$ 508
$1,110
$1,112

Slightly decreased shoreline exposure under Flood Control
Alternative would lower fugitive dust emission potential. Other
alternatives would have slightly increased potential for
increased fugitive dust emissions. Minimal changes in areawide fugitive dust emissions would be expected.

City of Page
Basin States
Flood Control
Six States
California
Shortage Protection

The increase over baseline conditions of annual pumping costs
for each alternative follows:
Navajo Generating Station
Basin States
$2,216
Flood Control
$
0
Six States
$2,129
California
$4,651
Shortage Protection
$4,660

CHAPTER 2

2-29

There is a probability of shortages of CAP
priority water for tribes in central Arizona.

The water available to members of Ten Tribes
Partnership would not be affected by future
changes under baseline conditions.

Not significant due to past water level
fluctuations. Impacts have already occurred.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Effects on water supply for Indian
Tribes and Communities

Indian Trust Assets

Effects on Historic Properties in
Operational Zone of Reservoir and
River Reaches.

Cultural Resources

Fugitive Dust Emissions from
Exposed Reservoir Shoreline

Greater probability of shortages of CAP priority water for tribes
in central Arizona under all alternatives with the exception of the
Flood Control Alternative.

No effect on water available to members of Ten Tribes
Partnership.

Not significant due to past water level fluctuations. Impacts
have already occurred.

ior
Inter 17
e
Potential for fugitive dust emissions
of th 29, 20
pt.
from shoreline exposure at Lake Mead
. De ember
v
and Lake Powell.
ation on Nov
Visual Resources
N
vajo hived
Visual Attractiveness of Reservoir
Increased probability of temporary degradation
Flood Control Alternative: Same as baseline conditions.
Scenery, Lake Mead and Lake
in visual attractivenessc shoreline vistas
in Na 4, ar of
Powell
from
lower
cited resulting86inincreasing potential forPowell. Other alternatives: Higher probability of degradation of visual
attractiveness through 2016 due to accelerated decline of
water6
-1 levels Lake Mead and Lake
Potential effects of lower reservoir
minimum reservoir levels.
4
1
elevations on scenic quality. No.

Air Quality

Potential change in the cost of power
to pump Lake Powell water to the
Navajo Generating Station and the
City of Page.

Intake Energy Requirements at Lake
Powell

DESCRIPTION OF ALTERNATIVES

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2002 through 2016
2017 through 2050

2002 through 2016
2017 through 2050

Surplus:
Shortage:

0%
0%

26%
19%

100%
100%

Probability of excess flows below Morelos Dam
would gradually decline under baseline
conditions.

2002 through 2016
2016 through 2050

Normal:

No effects are anticipated.

Flood Control Alternative: Similar to baseline.

The Flood Control Alternative would provide slightly higher (1%)
probabilities of surplus than under baseline conditions 2016.
The rest of the alternatives provide slightly lower (3% to 7%)
probabilities of surpluses through 2016 and about the same
level as baseline through 2050. Deliveries less than the treaty
apportionment (1.5 mafy) do not occur under the alternatives at
any time through 2050.

No effects anticipated.

CHAPTER 2

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Amount of excess flow that may reach
the Colorado River delta.

2-30

Other alternatives: Small reduction in probability of excess
flows.

r
terio
InStates Alternative there would be no effect on
Potential Effects on Species and
Probability of excess flows below Morelos Dam
Under the
1 clapper
of the BasinVaquita, Yuma7 rail, California
Habitat in Mexico
would gradually decline.
desert
t.Clarks pupfish,and9, 2is0 likely to be any adverseblack rail,
p
ber 2
v. De vtotoaba, Southwestern willow flycatcher, Yellow-billedaffect on
mgrebe; there not
cuckoo,
n
e
Natio d on No Elf owl or Bell's vireo.
jomodeling ofve
1. Effects identified are based on probabilities developedva
through
discussed in detail in Chapter
Na throughaconditionspossiblebefuture conditionsnear 2016,2050,year in which the interim surplus3.criteria would
greatest at or
the
2. In general, the differences between the alternatives and baseline chi would
n
terminate.
ted i 686lake r
c essentially full when the 4, elevation reaches 3695 feet msl (5 feet below the top of the spillway gates).
3. Lake Powell is considered to be i
-1
4. Probabilities of shortage are based on the modeling assumption of protecting a Lake Mead elevation of 1083 feet msl. There are no established shortage criteria for the
operation of Lake Mead.
o. 14
N

Flow Below Morelos Dam

Probabilities of meeting Treaty delivery
obligations

Treaty Water Delivery Obligations

Transboundary Effects

Exposure of Minority or Low Income
Communities to Health or
Environmental Hazards

Environmental Justice

DESCRIPTION OF ALTERNATIVES

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ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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3
AFFECTED ENVIRONMENT
AND ENVIRONMENTAL CONSEQUENCES
3.1 INTRODUCTION
Chapter 3 presents the analysis conducted and identifies potential effects that could
occur as a result of implementation of the interim surplus criteria alternatives under
consideration. Section 3.1 describes the: 1) structure of the resource sections in this
chapter; 2) role of modeling in the analysis; 3) baseline used for measuring potential
effects of the alternatives; 4) general approach used for determining potential effects;
5) period of analysis; and 6) environmental commitments associated with interim
surplus criteria.
Section 3.2 presents a general discussion of the geographic area within which potential
effects of the interim surplus criteria were analyzed, and Section 3.3 describes the
modeling methods and general results of Colorado River system modeling. The
remaining sections of Chapter 3 present resource-specific analyses of potential effects
using information obtained from the modeling.
rior

Inte
f the 9, 2017
3.1.1 STRUCTURE OF RESOURCE SECTIONS o
pt.
. De ember 2
v
ion v chapter
Beginning with Section 3.4, the jo Nat in this n No each present a general resource
sections
arecreationed o
v
iv
category, such as water supply,
in Na
arch and aquatic resources. Within each resource
d analyses 4, one or more specific issues identified for
ite
category is contained
c
1686 of
consideration through scoping, public review and comment, and internal review. A
. 14No
discussion of the methodology, affected environment and environmental consequences
is provided for each issue. Environmental commitments are proposed for impacts to
various resource issues as appropriate.
Methodology discussions identify the specific methods used for determining the
affected environment and potential environmental consequences of the alternatives.
The affected environment discussions then identify the specific context within which
the issue being analyzed exists. This includes a discussion of general environmental
characteristics associated with each issue, as well as important Colorado River system
conditions that may be associated with each issue. Finally, the potential effects of
interim surplus criteria compared to baseline conditions (as discussed in more detail
below) are presented in the environmental consequences discussions.
3.1.2

USE OF MODELING TO IDENTIFY POTENTIAL FUTURE
COLORADO RIVER SYSTEM CONDITIONS

To determine the potential effects of the interim surplus criteria alternatives, modeling
of the Colorado River system was conducted (a complete description of the modeling

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.1-1

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

procedure is included in Section 3.3). Modeling provides projections of potential future
Colorado River system conditions (i.e., reservoir surface elevations, river flows,
salinity, etc.). The modeling results allow a comparison of potential future conditions
under the various interim surplus criteria alternatives and baseline conditions. As such,
much of the analyses contained within this FEIS are based upon potential effects of
changed flows and water levels within the Colorado River and mainstream reservoirs.
3.1.3

BASELINE CONDITIONS

As discussed in Chapter 2, the No Action Alternative does not provide consistent
specific criteria for determining surplus conditions. As such, it is not possible to
precisely model the No Action Alternative. However, in order to provide a reasonable
analytical projection of potential future system conditions without interim surplus
criteria, a baseline surplus strategy (70R) was utilized. This baseline represents
definable surplus criteria based on recent operational decisions. The 70R strategy is
based upon recent secretarial operating decisions and was modeled to develop a
projection of baseline conditions for comparison with the alternatives in this FEIS.
3.1.4

IMPACT DETERMINATION

rior

The analysis of potential effects for each issue considered ishe Intprimarily upon the
based e
7
f t important1to each issue,
results of modeling. Following the identification ofpt. o
conditions 29, 20
. De
ber
the potential effects of various system conditions overvthe general range of their
ion v No em
Nat
possible occurrence (as identified by the range of modeling output for various
vajo issue.ved on
parameters) are identifiedNa each rchi The potential effects of the various interim
d in for , a
surplus criteria cite -16864
alternatives are then presented in terms of the incremental differences in
probabilities (or o. 14 circumstances associated with a given probability) between
N projected
baseline conditions and the alternatives.
3.1.5

PERIOD OF ANALYSIS

This FEIS addresses interim surplus criteria that would be used during the years 2001
through 2015 for determining whether surplus water would be available during the
years 2002 through 2016. Due to the potential for effects beyond the 15-year interim
period, the modeling and impact analyses extend through the year 2050. It is important
to note that modeling output and associated impact analyses become more uncertain
over time as a result of increased uncertainty of future system conditions (including
hydrologic conditions), as well as uncertainty with regard to future operational
decisions that will affect circumstances within the Colorado River system.
3.1.6

ENVIRONMENTAL COMMITMENTS

As discussed, impacts identified in Chapter 3 are associated with changes in the
difference between probabilities of occurrence for specific resource issues under study
when comparing the action alternatives to baseline conditions. Reclamation has

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.1-2

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

determined that most of the potential impacts identified are not of a magnitude that
would require specific mitigation measures to reduce or eliminate their occurrence
because the small changes in probabilities of occurrence are within Reclamation’s
current operational regime and authorities under applicable federal law. However, in
recognition of potential effects that could occur under baseline conditions or with
implementation of the interim surplus criteria alternatives under consideration,
Reclamation has developed a number of environmental commitments that would be
undertaken if interim surplus criteria are implemented. These commitments are
described in relevant resource sections of this Chapter and in Section 3.17.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.1-3

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

3.2

CHAPTER 3

POTENTIALLY AFFECTED AREA

Interim surplus criteria could affect the operation of the Colorado River system (i.e.,
reservoir levels and river flow volumes) as a result of surplus determinations and
associated water deliveries that may not have occurred in the absence of such criteria.
This section describes the general geographic scope in which specific issues and
potential effects associated with the interim surplus criteria alternatives were considered
in this FEIS. Also discussed are the AMP, and how the program influences flows
between Lake Powell and Lake Mead.
In addition to influencing conditions within the Colorado River system, it is recognized
that continued delivery of surplus water that could result from interim surplus criteria
would complement ongoing and proposed state actions in the Lower Basin. These
actions could result in environmental effects outside of the river corridor. However,
these actions have independent utility and are not caused by or dependent on interim
surplus criteria for their implementation. Environmental compliance would be required
on a case-by-case basis prior to their implementation. Therefore, Reclamation
determined that the appropriate scope of this analysis is to consider only those potential
effects that could occur within the Colorado River corridor as defined by the 100-year
r
flood plain and reservoir maximum water surface elevations.
terio

e In
7
of h 29, 2 Water
. andthydrology. 01 supply to
pt
Interim surplus criteria are based on system conditions
. De
ber
the Lower Division states of Arizona,ation v and Nevada is achieved primarily
California Novem
N Mead.
through releases and pumping ajo Lake ed on As a result of Lake Powell and Lake
from
iv
Nav (discussed further in Section 3.3), interim surplus
in
Mead equalization requirements, arch
ited 6864
c
criteria effects on Lake-Mead surface elevations could also influence Lake Powell
14 1
o.and Glen Canyon Dam releases. However, operation of the other
N
surface elevations

Upper Basin reservoirs is independent of Lake Powell. Therefore, the upstream limit of
the potentially affected area under consideration in this FEIS is the full pool elevation of
Lake Powell. The downstream limit of the potentially affected area within the United
States is the SIB between the United States and Mexico. Section 3.16 of this FEIS
addresses potential transboundary impacts in Mexico extending to the mouth of the
Colorado River as required pursuant to Executive Order 12114 - Environmental Effects
Abroad of Major Federal Actions, January 4, 1997, and the July 1, 1997 Council on
Environmental Quality (CEQ) Guidelines on NEPA Analyses for Transboundary
Impacts.
3.2.1

COLORADO RIVER SEGMENTS AND ISSUES ADDRESSED

As shown on Map 3.2-1, the Colorado River corridor from Lake Powell to Mexico
consists of flowing river reaches, two large reservoirs (Lake Powell and Lake Mead)
and two smaller reservoirs downstream of Lake Mead (Lake Mohave and Lake
Havasu). The river corridor and adjacent areas comprise a heterogeneous composite of
various geographic and hydrologic regimes, which differ in their resource composition
and resource management administration.

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Map 3.2-1
Area of Potential Effect

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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For the purposes of presentation, and to focus analysis of the potential effects of the
interim surplus criteria, the river corridor has been divided into four areas: Lake
Powell, the Colorado River between Glen Canyon Dam and Lake Mead, Lake Mead,
and the Colorado River between Hoover Dam and the SIB. The following sections
discuss the areas segmented for this analysis and introduce the issues considered within
each area.
3.2.1.1

LAKE POWELL

Lake Powell is a large reservoir on the Colorado River formed by Glen Canyon Dam.
The reservoir is narrow and long (over 100 miles). Lake Powell provides water storage
for use in meeting delivery requirements to the Lower Basin.
The normal operating range of Lake Powell is between elevations 3490 and 3700 feet
msl. Elevation 3490 feet msl corresponds to minimum power pool. (Releases from
Glen Canyon Dam can be made below 3490 feet msl down to elevation 3370 feet msl
via the river bypass tubes.) Elevation 3700 feet msl corresponds to the top of the
spillway radial gates. During floods, the elevation of Lake Powell can go above
3700 feet msl by raising the radial spillway gates, resulting in spillway releases. In
1983, Lake Powell reached a high elevation of 3708.34 feet msl.
rior

Inte
f the 9, 2017
Lake Powell is located within the GCNRA, whichepadministered by the NPS.
is t. o
r
. D operation of 2 Canyon Dam and
Reclamation retains authority and discretion v the vembe Glen
ion for No
Nat d on
Lake Powell. Issues considered jin this FEIS associated with Lake Powell include:
va o surface elevations); salinity; aquatic resources;
ive
hydrology (i.e., projectedNa
d in reservoir rch
, afacilities, boating and sport fishing; power
cite 16864
special-status species; recreational
generation from o. 14
N Glen Canyon Dam; changes in pumping costs for Navajo Generating
Station and the City of Page; visual and air quality effects associated with exposed
reservoir shoreline; environmental justice; cultural resources; and Indian Trust Assets
(ITAs).
3.2.1.2

COLORADO RIVER FROM GLEN CANYON DAM TO LAKE MEAD

The segment of the Colorado River between Glen Canyon Dam and Lake Mead is
comprised of a narrow river corridor through the Grand Canyon that is administered
primarily by the Grand Canyon National Park. Flows within this reach of the river
consist primarily of releases from Glen Canyon Dam as discussed in Section 3.3.1.
Issues considered in this FEIS within this segment of the river address those associated
with a program of low steady summer flows and Beach/Habitat-Building Flow (BHBF)
releases, as discussed in Section 3.2.2.
3.2.1.3

LAKE MEAD

Lake Mead is a large reservoir on the Colorado River formed by Hoover Dam. The
reservoir provides water storage for use in regulating the water supply and meeting

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delivery requirements in the Lower Basin. The normal operating range of the reservoir
is between elevations 1219.61 and 1083 msl. Elevation 1083 msl corresponds to the
minimum power pool. (Releases can be made from Hoover Dam below 1083 msl down
to 895 feel msl via the intake towers.) During floods, the elevation of Lake Mead can
go above 1219.61 msl. The top of the raised spillway gates is at 1221.0 msl. Since its
initial filling in the late 1930s, the reservoir water level has fluctuated from a high of
1225.85 feet msl (as occurred in July, 1983) to a low of 1083.21 feet msl (as occurred in
April, 1956).
The reservoir is located within the LMNRA, which is administered by the NPS.
However, Reclamation retains authority and discretion for the operation of Hoover Dam
and Lake Mead. Issues considered in this FEIS associated with Lake Mead include:
hydrology; water supply for Nevada; salinity; water quality associated with Las Vegas
Wash and SNWA intakes; aquatic resources; special-status species; recreational
facilities, boating and sport fishing; power generation from Hoover Dam; visual and air
quality effects associated with exposed reservoir shoreline; environmental justice;
cultural resources; and ITAs.
3.2.1.4

COLORADO RIVER FROM HOOVER DAM TO THE SOUTHERLY
INTERNATIONAL BOUNDARY
erior

Int
7
f thewithin201shallow
The Colorado River from Hoover Dam to the SIBepcontained r 29, the
is t. o
v. D
mbe
Colorado River Valley in which Lake Mohave, Lake Havasu and other smaller
ation segment,ve
No especially along river reaches
diversion reservoirs are located. jo N this on
ava Within ved
below Parker Dam, d in N
the Colorado River iis fringed with riparian vegetation and marshy
arch
te
cicontains 6864, of diversion dams and a system of levees. The
backwaters, and
4-1 a number
northern reachNothis segment, including Lake Mohave, lies within the LMNRA. The
of . 1
lower reach is bordered by a combination of federal, Tribal and private land. The last 22
miles (approximately) is along the international border with Mexico. Reclamation
retains authority and discretion for river operations in the reaches of this segment.
Under the BCPA and the Decree, discussed previously in Chapter 1, releases from
Hoover Dam are governed by orders for downstream water deliveries to Arizona,
California, Nevada and Mexico. However, releases may exceed orders when flood
releases are required under the Corps’ flood control criteria, as discussed in Chapter 1
or for other purposes consistent with the BCPA and the Decree.
Issues considered in this FEIS associated with this river segment include hydrology;
water supply for Arizona, California, Nevada and Mexico; costs of flood damages
downstream of Hoover Dam; water quality; potential effects of changes in flows on
special-status species; potential effects of changes in the temperature of water released
from Hoover Dam on sport fisheries and fishing; environmental justice; cultural
resources; and ITAs.

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3.2.2

CHAPTER 3

ADAPTIVE MANAGEMENT PROGRAM INFLUENCE ON GLEN
CANYON DAM RELEASES

In March 1995, Reclamation completed an EIS on the operation of Glen Canyon Dam.
The EIS developed and analyzed alternative operation scenarios designed to meet
statutory responsibilities for conserving downstream resources, while meeting other
authorized project purposes, and protecting Native American interests. Major issues of
concern included native and endangered species, beach erosion, recreation (including
white-water boating, sport fishing, and camping), vegetation, wildlife habitat and food
base, water supply, hydroelectric power generation, cultural resources, and Native
American interests. The Secretary signed a ROD on October 8, 1996, which specified
certain types of releases from Glen Canyon Dam. Prior to the ROD, Glen Canyon Dam
was operated as a peaking power facility, maximizing the value of power produced.
The patterns of releases resulting from this type of operation were recognized to be
detrimental to downstream resources and were therefore modified by the ROD.
Reclamation also consulted with the Service under the ESA. The Service issued a
biological opinion containing a recommendation for a reasonable and prudent
alternative, which was incorporated into the ROD (see Section 1.4.2.1).
To determine if the operation of Glen Canyon Dam under the RODerimeeting the
is or
Int as 17
objectives of downstream resource protection, an AMP washe
instituted 0 described in
of t
9 2
Section 1.4.2.1. Through this process, the effects epdam operations, and the status of
of t.
. Dare used to er 2
b formulate potential
em
resources are monitored and studied. ation v
The results
N refinements Nov operations to ensure that the
n to dam
recommendations to the Secretary on ved o
vajo
in Na 4, archi Act are met. As long as the AMP continues
purposes of the Grand Canyon Protection
ited
6
to successfully c
function,168natural and cultural resources within the Colorado River
the
. 14corridor between Glen Canyon Dam and Separation Canyon (just upstream of Lake
No
Mead) will be protected and conserved.
Two types of releases from Glen Canyon Dam, BHBFs and low steady summer flows,
are part of a program of experimental flows being developed and refined through the
AMP, as called for in the Biological Opinion (USFWS, 1994). The change in the
frequency with which BHBFs and low steady summer flows would be triggered under
each of the alternatives has been analyzed (see Section 3.6). Flows from Glen Canyon
Dam, which could be affected by the adoption of interim surplus criteria, will remain
within the range of flows analyzed in detail in the Glen Canyon Dam EIS. Therefore,
effects of potential changes in the frequencies of these flows on downstream resources
require no further analysis outside of the Glen Canyon Dam ROD and the AMP.

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3.3 RIVER SYSTEM OPERATIONS
This section addresses the operation of the Colorado River system, the modeling process
used to simulate river operation and potential changes that may occur from implementation
of the interim surplus criteria. The term system management refers to how the water is
managed once it enters the Colorado River system and includes operation of the system
reservoirs, dams and other Colorado River system facilities. The environmental and
socioeconomic effects of the interim surplus criteria alternatives stem from changes in
the operation of the Colorado River system under the surplus alternatives relative to the
baseline conditions.
3.3.1

OPERATION OF THE COLORADO RIVER SYSTEM

Operation of the Colorado River system and delivery of Colorado River water to the
seven Basin States and Mexico are conducted in accordance with the Law of the River
as discussed in Section 1.3.2.1. Water cannot be released from storage unless there is a
reasonable beneficial use for the water. The exceptions to this are releases required for
flood control, river regulation or dam safety. In the Lower Basin, water is released from
the system to satisfy water delivery orders and to satisfy other purposes set forth in the
Decree. The principal facilities that were built to manage the watererior Colorado
t in the
River System include Glen Canyon Dam and Hoover Dam.the In
017
f

9, 2
pt. o
. De ember 2 LROC and the
The Colorado River system is operatedtbyn v
Reclamation pursuant to
Nov
Na io d The AOP is formulated for the upcoming
AOP. The AOP is required byajo CRBPA. on
the
av
ive
year under a varietyd in N
of potential ,scenarios or conditions. The plan is developed based
arch
cite existing4
on projected demands, -1686 storage conditions and probable inflows. The AOP is
14
prepared by Reclamation, acting on behalf of the Secretary, in consultation with the
No.

Basin States, the Upper Colorado River Commission, Indian tribes, appropriate federal
agencies, representatives of the academic and scientific communities, environmental
organizations, the recreation industry, water delivery contractors, contractors for the
purpose of federal power, others interested in Colorado River operations, and the
general public.
Prior to the beginning of the calendar year, Lower Basin diversion schedules are
requested from water users entitled to Colorado River water as discussed in Section 3.4.
These schedules are estimated monthly diversions and return flows that allow
Reclamation to determine a tentative schedule of monthly releases through the Hoover
Powerplant. Actual monthly releases are determined by the demand for water
downstream of Hoover Dam. Daily changes in water orders are made to accommodate
emergencies, temperature and weather.
A minimum of 1.5 maf is delivered annually to Mexico in accordance with the Treaty.
The Treaty contains provisions for delivery of up to 200,000 af above the 1.5 maf when
there exists water in excess of that necessary to satisfy the uses in the United States and
the guaranteed quantity of 1.5 maf to Mexico. Additionally, excess flows above the

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200,000 af may become available to Mexico coincident with Lake Mead flood control
releases and Gila River flood flows provided that the reasonable beneficial uses of the
Lower Division states have been satisfied.
3.3.1.1 OPERATION OF GLEN CANYON DAM
Flows below Glen Canyon Dam are influenced by storage and release decisions that are
scheduled and implemented on an annual, monthly and hourly basis from Glen Canyon
Dam.
The annual volume of water released from Glen Canyon Dam is made according to the
provisions of the LROC that includes a minimum objective release of 8.23 maf, storage
equalization between Lake Powell and Lake Mead under prescribed conditions and the
avoidance of spills. Annual releases from Lake Powell greater than the minimum occur
if Upper Basin storage is greater than the storage required by Section 602(a) of the
CRBPA, and if the storage in Lake Powell is greater than the storage in Lake Mead.
Annual release volumes greater than the minimum objective of 8.23 maf are also made
to avoid anticipated spills.
Monthly operational decisions are generally intermediate targets neededrto
terio
systematically achieve the annual operating requirements. The actual volume of water
he In 2017
of t
released from Lake Powell each month depends on pt. forecasted 9,
e the ber 2 inflow, storage
D
targets and annual release requirements idescribed above.m
Demand for energy is also
n v.
at othe annualove and storage requirements
considered and accommodatedajolong as d on N release
as N
v
ive
are not affected. d in Na
arch

cite 16864,
14The National Weather Service Colorado Basin River Forecast Center (CBRFC)
No.

provides the monthly forecasts of expected inflow into Lake Powell. The CBRFC uses
a satellite-telemetered network of hundreds of data collection points within the Upper
Colorado River Basin that gather data on snow water content, precipitation, temperature
and streamflow. Regression and real-time conceptual computer models are used to
forecast inflows that are then used by Reclamation to plan future release volumes. Due
to the variability in climatic conditions, modeling and data errors, these forecasts are
based, in part, on large uncertainties. The greatest period of uncertainty occurs in early
winter and decreases as the snow accumulation period progresses into the snowmelt
season, often forcing modifications to the monthly schedule of releases.
An objective in the operation of Glen Canyon Dam is to attempt to safely fill Lake
Powell each summer. When carryover storage from the previous year in combination
with forecasted inflow allows, Lake Powell is targeted to reach a storage of about 23.8
maf in July (0.5 maf from full pool). In years when Lake Powell fills or nearly fills in
the summer, releases in the late summer and early winter are generally made to draw the
reservoir level down, so that there is at least 2.4 maf of vacant space in Lake Powell on
January 1. Storage targets are always reached in a manner consistent with the LROC.

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Scheduling of BHBF releases from Glen Canyon Dam are discussed in Section 3.6.2.2.
Daily and hourly releases are made according to the parameters of the ROD for the
Operation of Glen Canyon Dam Final Environmental Impact Statement and published
in the Glen Canyon Dam Operating Criteria (62 CFR 9447, Mar. 3, 1997), as shown in
Table 3.3-1.
Table 3.3-1
Glen Canyon Dam Release Restrictions
Parameter
1

Maximum Flow
Minimum Flow

Ramp Rates
Ascending
Descending
2
Daily Fluctuations
1

Cubic Feet per Second
25,000
5,000
8,000
4,000
1,500
5,000 to 8,000

Conditions
Nighttime
7:00 a.m. to 7:00 p.m.
Per hour
Per hour

To be evaluated and potentially increased as necessary and in years when
delivery to the Lower Basin exceeds 8.23 maf.
Daily fluctuation limit is 5,000 cfs for months with release volumes less than
0.6 maf; 6,000 cfs for monthly release volumes of 0.6 maf to 0.8 maf; and
8,000 cfs for monthly volumes over 0.8 maf.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
3.3.1.2 OPERATION OF HOOVER Dchived
Nava ar AM
in
cited 16864,
Hoover Dam is managed to provide at least 7.5 maf annually for consumptive use by
14No.
the Lower Division states plus the United States’ obligation to Mexico. Hoover Dam
2

releases are managed on an hourly basis to maximize the value of generated power by
providing peaking during high-demand periods. This results in fluctuating flows below
Hoover Dam that can range from 1,000 cubic feet per second (cfs) to 49,000 cfs. The
upper value is the maximum flow-through capacity through the powerplant at Hoover
Dam (49,000 cfs). However, because these flows enter Lake Mohave downstream, the
affected zone of fluctuation is only a few miles.
Releases of water from Hoover Dam may also be affected by the Secretary’s
determinations relating to normal, surplus or shortage water supply conditions, as
discussed in Section 1.3.4.1. Another type of release includes flood control releases.
For Hoover Dam, flood control releases are defined in this FEIS as releases in excess of
the downstream demands.
Flood control was specified as a primary project purpose by the BCPA, the act
authorizing Hoover Dam. The Corps is responsible for developing the flood control
operation plan for Hoover Dam and Lake Mead as indicated in 33 CFR 208.11. The
plan is the result of a coordinated effort by the Corps and Reclamation. However, the
Corps is responsible for providing the flood control regulations and has authority for

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final approval of the plan. Any deviations from the flood control operating instructions
provided by the plan must be authorized by the Corps. The Secretary is responsible for
operating Hoover Dam in accordance with these regulations.
Lake Mead’s uppermost 1.5 maf of storage capacity, between elevations 1219.61 and
1229.0, is defined as exclusive flood control space. Within this capacity allocation,
1.218 maf of flood storage is above elevation 1221.0, which is the top of the raised
spillway gates.
Flood control regulations specify that once Lake Mead flood releases exceed 40,000 cfs,
the releases shall be maintained at the highest rate until the reservoir drops to elevation
1221.0 feet msl. Releases may then be gradually reduced to 40,000 cfs until the
prescribed seasonal storage space is available.
The regulations set forth two primary criteria for flood control operations related to
snowmelt: 1) preparatory reservoir space requirements, and 2) application of runoff
forecasts to determine releases.
In preparation for each annual season of snow accumulation and associated runoff,
progressive expansion of total Colorado River system reservoir space iis r
r o required during
the latter half of each year. Minimum available flood control e Inte
space increases from 1.5
017
f th
maf on August 1 to 5.35 maf on January 1. Requiredtflood storage space can be
p . o er 29, 2
. e emb
accumulated within Lake Mead and in specifiedD
ion v upstream reservoirs: Powell, Navajo,
at
Nov
Blue Mesa, Flaming Gorge and Fontenelle. d onminimum required to be reserved
ajo N ive The
Nav
exclusively for flood control storage chLake Mead is 1.5 maf. Table 3.3-2 presents the
d in 64, ar in
cite 1 storage space within the Colorado River system by date:
amount of required flood 68
-

No.

14

Table 3.3-2
Minimum Required Colorado River System Storage Space
Storage Volume
(maf)

Date
August 1
September 1
October 1
November 1
December 1
January 1

1.50
2.27
3.04
3.81
4.58
5.35

Normal space-building releases from Lake Mead to meet the required August 1 to
January 1 flood control space are limited to a maximum of 28,000 cfs. Releases in any
month based on water entitlement holders’ demand are much less than 28,000 cfs (on
the order of 20,000 cfs or less).

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Between January 1 and July 31, flood control releases, based on forecasted inflow, may
be required to prevent filling of Lake Mead beyond its 1.5 maf minimum space
requirement. Beginning on January 1 and continuing through July, the CBRFC issues
monthly runoff forecasts. These forecasts are used by Reclamation in estimating
releases from Hoover Dam. The release schedule contained in the Corps’ regulations is
based on increasing releases in six steps as shown on Table 3.3-3.
Table 3.3-3
Minimum Flood Control Releases at Hoover Dam
Step

Amount of Cubic Feet/Second

Step 1
Step 2
Step 3
Step 4
Step 5
Step 6

0
19,000
28,000
35,000
40,000
73,000

The lowest step, zero cfs, corresponds to times when the regulations do not require
flood control releases. Hoover Dam releases are then made to meeterior and power
t water
objectives. The second step, 19,000 cfs, is based on the powerplant capacity of Parker
he In 2017
of t
Dam. The third step, 28,000 cfs, corresponds toDept.
the Davis Dam 29,
.
ber Powerplant capacity.
The fourth step in the Corps release schedulevis 35,000 em This flow corresponds to
v cfs.
ion
Nat Hoover No
the powerplant flow-through vajo
capacity ofved onDam in 1987. However, the present
i
in Na
powerplant flow-through capacityarch
ited 6864, at Hoover Dam is 49,000 cfs. At the time Hoover
c
Dam was completed, 4-1 cfs was the approximate maximum flow from the dam
40,000
o. 1
N
considered to be nondamaging to the downstream streambed. The 40,000 cfs flow now
forms the fifth step. Releases of 40,000 cfs and greater would result from lowprobability hydrologic events. The sixth and final step in the series (73,000 cfs) is the
maximum controlled release from Hoover Dam that can occur without spillway flow.
Flood control releases are required when forecasted inflow exceeds downstream
demands, available storage space at lakes Mead and Powell and allowable space in
other Upper Basin reservoirs. This includes accounting for projected bank storage and
evaporation losses at both lakes, plus net withdrawal from Lake Mead by the SNWA.
The Corps regulations set the procedures for releasing the volume that cannot be
impounded, as discussed above.
Average monthly releases are determined early in each month and apply only to the
current month. The releases are progressively revised in response to updated runoff
forecasts and changing reservoir storage levels during each subsequent month
throughout the January 1–July 31 runoff period. If the reservoirs are full, drawdown is
accomplished to vacate flood control space as required. Unless flood control is
necessary, Hoover Dam is operated to meet downstream demands.

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During non-flood operations, the end-of-month Lake Mead elevations are driven by
consumptive use needs, Glen Canyon Dam releases and Treaty deliveries to Mexico.
Lake Mead end-of-month target elevations are not fixed as are the end-of-month target
elevations for Lake Mohave and Lake Havasu. Normally, Lake Mead elevations
decline with increasing irrigation deliveries through June or later and then begin to rise
again. Lake Mead’s storage capacity provides for the majority of Colorado River
regulation from Glen Canyon Dam to the border with Mexico.
3.3.2

NATURAL RUNOFF AND STORAGE OF WATER

Most of the natural flow in the Colorado River system originates in the Upper Basin and
is highly variable from year to year. The natural flow represents an estimate of runoff
flows that would exist without storage or depletion by man and was used in the
modeling of the baseline conditions and interim surplus criteria alternatives. About 86
percent of the Colorado River System annual runoff originates in only 15 percent of the
watershed—in the mountains of Colorado, Utah, Wyoming and New Mexico. While
the average annual natural flow at Lees Ferry is calculated at 15.1 maf, annual flows in
excess of 23 maf and as little as 5 maf have occurred. The flow in the Colorado River
above Lake Powell reaches its annual maximum during the April through July period.
During the summer and fall, thunderstorms occasionally produce additional peaks in the
ior
Inter 17 peaks and
river. However, these flows are usually smaller in volume the the snowmelt
than
20
of
pGlen Canyon9Dam consist almost
of much shorter duration. Flows immediately below t.
e
r2 ,
.D
mbe
entirely of water released from Lake Powell.vDownstream of Glen Canyon Dam, the
ation on Nove
o
annual river gains from tributaries, N ved discharge and occasional flash floods
avaj groundwater
in N900,000raf. iImmediately downstream of Hoover Dam, the
from side canyonsed
average
a ch
cit almost6864, of water released from Lake Mead. Downstream of
river flows consist 4-1 entirely
1
Hoover Dam, the river gains additional water from tributaries such as the Bill Williams
No.
River and the Gila River, groundwater discharge, and return flows.
Total storage capacity in the Colorado River system is nearly four times the river’s
average natural flow. The various reservoirs that provide storage in the Colorado River
system and their respective capacities were discussed in Section 1.3.2.
Figure 3.3-1 presents an overview of the historical natural flow calculated at Lees Ferry
for calendar years 1906 through 1999. The natural flow represents an estimate of the
flows that would originate or exist above Lees Ferry without storage or depletion by
man. This is different than the recorded or historical stream flows that represent actual
measured flows. Figure 3.3-2 presents an overview of the historical flows recorded at
Lees Ferry for the period 1922 through 1999 (calendar year).

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-6

1905

1910

1915

Running Average

10 Year Average

Flow (maf)

1920

1925

1930

1935

1940

1945

1955

3.3-7

Year

1950

1960

1965

1970

1975

1980

1985

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5

10

An
nu 15
al
Flo
w
(m
af)

20

25

Figure 3.3-1
Natural Flow at Lees Ferry Stream Gage

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

1990

1995

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0
1905

5

10

15

20

25

1910

1915

1920

1925

1930

1935

1940

1945

1955

3.3-8

Year

1950

1960

1965

1970

1975

1980

1985

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Running Average

10 Year Average

Flow (maf)

Figure 3.3-2
Historic Annual Flow at Lees Ferry Stream Gage

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Flow (ma

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

1990

1995

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3.3.3

CHAPTER 3

MODELING AND FUTURE HYDROLOGY

3.3.3.1 MODEL CONFIGURATION
Future Colorado River system conditions under baseline conditions and the surplus
alternatives were simulated using a computerized model. The model framework used
for this process is a commercial river modeling software called RiverWare. RiverWare
was developed by the University of Colorado through a cooperative process with
Reclamation and the Tennessee Valley Authority. RiverWare was configured to
simulate the Colorado River System and its operation and integrates the Colorado River
Simulation System (CRSS) model that was developed by Reclamation in the early
1970s. River operation parameters modeled and analyzed include the water entering the
river system, storage in system reservoirs, releases from storage, river flows, and the
water demands of and deliveries to the Basin States and Mexico.
The water supply used by the model consists of the historic record of natural flow in the
river system over the 85-year period from 1906 through 1990, from 29 individual
inflow points on the system.
Future Colorado River water demands were based on demand and depletion projections
riorthe
In from 17 river less
prepared by the Basin States. Depletions are defined as diversionste
f the
return flow credits, where applicable. Return flow credits are applied20 a portion of
pt. o er 29, when
e
b
the diverted water is returned to the riveron v. D In cases where there are no return
i system. Novem
at the depletion is equal to the diversion. The
flow credits associated with the jo N
vadiversions, d on
NaCanyon chiveHoover Dam and other elements of the
simulated operationd in
of Glen
, ar Dam,
ite
Colorado Rivercsystem-was864
consistent with the LROC, applicable requirements for
16
storage and flood control management, water supply deliveries to the Basin States,
o. 14
N
Indian tribes, and Mexico, and flow regulation downstream of the system dams.
3.3.3.2 INTERIM SURPLUS CRITERIA MODELED
As discussed in Chapter 2, seven operational scenarios are considered in this FEIS. The
seven scenarios considered and modeled consist of two different baseline conditions
and the five surplus alternatives. The two baseline conditions are similar except that
one includes the modeling of California’s intrastate water transfers while the other does
not. The five surplus alternatives consist of the Basin States, Flood Control, Six States,
California and the Shortage Protection alternatives.
Surplus deliveries to the Lower Division states and Mexico are provided under baseline
conditions and all surplus alternatives. Common to baseline conditions and all
alternatives, a surplus is determined when flood control releases are made from Lake
Mead. As a general modeling assumption, Mexico receives surplus deliveries only
under this condition.

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As noted above, two different baseline conditions were modeled and evaluated (baseline
conditions with transfers and baseline conditions without transfers). The normal
schedules of the three California entities involved in the transfers (Metropolitan Water
District, Imperial Irrigation District, and Coachella Water Valley District) are tabulated
in Attachment H. The comparative analysis of the two baseline conditions is presented
in Attachment L. The baseline conditions with transfers were selected for use in the
comparative analysis of the surplus alternatives. The reason for this is a desire to
maintain consistency. All of the surplus alternatives include intrastate water transfers
and therefore, it was prudent to compare the baseline conditions with transfers to focus
and isolate the potential impacts of the interim surplus criteria from that of transfers.
3.3.3.3 GENERAL MODELING ASSUMPTIONS
Definitions and descriptions of the baseline conditions and the surplus alternatives and
their operational criteria were provided in Chapter 2. The modeling of river system
operations for the analysis presented in this FEIS also required certain assumptions
about various aspects of water delivery and system operation. Some important
modeling assumptions are listed below. Other modeling details and assumptions are
presented in Attachment J.

ior
Inter 17
Assumptions Common to Baseline and All Alternatives:the
20
of
ept. ber 29,
v. D v m
• The current Upper Basin reservoir operating rules are equivalent under all
ation conditions.e
No
surplus alternatives andjo N
va the baseline on
ed
chiv
in Na
• The Lake Mead flood4, ar procedures are always in effect.
ited 686 control
c
-1
• Reservoir starting conditions (all system reservoirs) are based on projected water
o. 14
N
level elevations for January 1, 2002. Reclamation’s 24 month study model (also
a model implemented in RiverWare) was used to project these elevations, using
actual elevations as of August 2000 and projected operations for the 2001 water
year.

•

The Upper Basin States' depletion projections are as provided by the Upper
Colorado River Commission (December 1999) and subsequently modified to
include new Indian tribe schedules provided during the preparation of the DEIS.
(See Attachments K and Q.)

•

Water deliveries to Mexico are pursuant to the requirements of the Treaty. This
provides minimum annual deliveries of 1.5 maf to Mexico and up to 1.7 maf
under Lake Mead flood control release conditions.

•

Mexico’s principal diversion is at Morelos Dam where most of its Colorado
River apportionment of 1.5 maf is diverted. In practice, up to 140 thousand acrefeet (kaf) is delivered to Mexico near the Southerly International Boundary
(SIB). The model, however, extends to just south of the Northerly International
Boundary (NIB) to include the diversion at Morelos Dam and accounts for the

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entire Treaty delivery at that point. Under normal conditions, the model sets the
diversion and depletion schedule for the Mexican Treaty delivery at Morelos
Dam to 1.515 mafy. The additional 15,000 af accounts for typical scheduling
errors and over-deliveries.
•

The modeled Colorado River water deliveries under the baseline conditions and
surplus alternatives assumed that all Arizona shortages would be absorbed by the
Central Arizona Project. Reclamation acknowledges that under the current
priority framework, there would be some sharing of Arizona shortage between
the Central Arizona Project and other Priority 4 users. However, the bases or
formula for the sharing of Arizona shortages is the subject of current negotiations
and as such, could not be adequately modeled for the FEIS. The water supply
conditions modeled for the FEIS were used to evaluate the relative differences in
water deliveries to each state under baseline conditions and the surplus
alternatives. The normal, surplus and shortage condition water depletion
schedules modeled in the FEIS are consistent with the depletion schedules
prepared by the Basin states for this purpose.

•

For the modeling presented in the FEIS, the Yuma Desalting Plant depletion
schedule for bypass to Mexico was set to 120,000 acre-feet per year (afy) from
or
2002-2021, representing the water provided by the U.S. to teriCienega. For
In the Treaty delivery.
modeling purposes, this depletion is not counted astpart of the2017
f he
pt. o 2022, 9,
2
The desalting plant is assumed to operate e
v. D beginning er reducing the bypass to
n purposes,vemb
52,000 afy. Similarly, for modeling
atio on No this depletion is not counted as
ajo N should be noted that the United States recognizes
v
part of the Treaty delivery. Ithived
n Na
arc
d iobligation,to replace, as appropriate, the bypass flows and the
that itcitean
has
864 for modeling purposes, do not necessarily represent
assumptions4-16 herein,
1 made
No.
the policy that Reclamation will adopt for replacement of bypass flows. The
assumptions made with respect to modeling the bypass flows are intended only
to provide a thorough and comprehensive accounting of Lower Basin water
supply. The United States is exploring options for replacement of the bypass
flows, including options that would not require operation of the Yuma Desalting
Plant.

•

Lake Mead is operated to meet depletion schedules provided by the Lower
Division states, Indian tribes, and Mexico. (See Attachments H and Q.)

•

Lake Mohave and Lake Havasu are operated in accordance with their existing
rule curves.

•

The water supply conditions modeled under the surplus alternatives and baseline
conditions considered the intrastate water transfers being planned by California.

•

There are no established shortage criteria that define when Lower Basin water
users would receive shortage condition deliveries. However, the model is
configured to provide approximately an 80 percent protection for Lake Mead
water elevation of 1083 feet msl (minimum power generation elevation).

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Assumptions Specific to Surplus Alternatives:
•

The respective surplus criteria for the surplus alternatives are assumed to be
effective for a specified period of 15 years. The effective period that was
modeled is defined as the 15-year period beginning on January 1, 2002 and
ending December 31, 2016. At the conclusion of the 15-year period, the
modeled operating criteria for each of the surplus alternatives is assumed to
revert to the operating criteria used to model baseline conditions (baseline
conditions with transfers).

•

The surplus depletion schedules for Arizona, California and Nevada vary
under each surplus alternative and the baseline conditions and are presented in
Attachment H.

3.3.3.4 LAKE MEAD WATER LEVEL PROTECTION ASSUMPTIONS
There are no established shortage criteria for the operation of Lake Mead. However, it
was necessary to include some shortage criteria in the model simulation to address
concerns related to low Lake Mead water levels. Three important Lake Mead water
elevations were selected for analysis. The significance of these selected elevations
r
relates to known economic and/or socioeconomic impacts that wouldroccur if Lake
te io
InElevation 1083 feet
e
Mead water levels were lowered below the selected waterf levels.
o th 29, 2017
msl is the minimum water level for effective power pt.
generationrat the Hoover
. De Elevation 1050 feet msl is the
be
Powerplant based on its existing turbineion v
configuration. em
at
Nov upper water intake. Water
o operation onSNWA's
minimum water level necessary jforN
of
Nava throughivedintake is delivered to Las Vegas Valley,
in Mead , arch this
withdrawn from thed
Lake
4
cite 168 of
Boulder City and other-parts 6 Clark County. Even though SNWA has constructed a
4
1
second intake No.lower elevation, the original intake at elevation 1050 feet msl is
at a
needed to meet full SNWA summer diversions. Elevation 1000 feet msl is the
minimum water level necessary for operation of SNWA’s lower water intake.
In the absence of specific shortage criteria, the Lake Mead level protection assumptions
listed below were applied by the model to facilitate the evaluation of the baseline
conditions and surplus alternatives.
First Level Shortage:
•

The Lake Mead water level of 1083 feet msl was designated as a level that
should be protected. Operation simulations were performed to develop a
“protection line” to prevent the water level from declining below elevation
1083 feet msl with approximately an 80 percent probability (see Section
3.3.4.1). The use of an alternative 1050-foot protection line is discussed in
Attachment M.

•

A shortage would be determined to exist when the Lake Mead water level
dropped below the protection line for elevation 1083 feet msl.

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•

CHAPTER 3

During first level shortage conditions, the annual water delivery to CAP was set
to 1.0 maf, and the SNWA was assigned four percent of the total shortage.

Second Level Shortage:
•

A second level shortage would be determined to exist when the Lake Mead
water surface elevation declined to 1000 feet msl.

•

During second level shortage conditions, the CAP and SNWA consumptive use
would be reduced as needed to maintain the Lake Mead water level at 1000 feet
msl. Once the delivery to the CAP is reduced to zero, deliveries to MWD and to
Mexico would be reduced to maintain the Lake Mead water level at 1000 feet
msl. Such reductions to MWD and Mexico did not occur in the simulations
conducted as part of this FEIS.

3.3.3.5 COMPUTATIONAL PROCEDURES
The model was used to simulate the future state of the Colorado River system on a
monthly basis, in terms of reservoir levels, releases from the dams, hydroelectric energy
generation, flows at various points along the system and diversions to and return flows
from various water users. The input data for the model included the monthly tributary
ior
Inter rates for each
inflows, various physical process parameters (such as the evaporation 17
0
f the
reservoir) and the diversion and depletion schedules foro
pt. entities in9, 2
e
r 2 the Basin States and
be
v. D
Mexico. The common and specific operating criteria vemalso input for each
ation on Nowere
N
alternative being studied.
vajo
ed

in Na
rchiv
ited in6864, a criteria for the baseline conditions and each
c
Despite the differences-1 the operating
14
surplus alternative, the future state of the Colorado River system (i.e., water levels at
No.

Lake Mead and Lake Powell) is most sensitive to the future inflows. As discussed in
Section 3.3.2, observations over the period of historical record (1906–present) show that
inflow into the system has been highly variable from year to year. Predictions of the
future inflows, particularly for long-range studies, are highly uncertain. Although the
model does not predict future inflows, it can be used to analyze a range of possible
future inflows and to quantify the probability of particular events (i.e., lake levels being
below or above certain levels).
Several methods are available for ascertaining the range of possible future inflows. On
the Colorado River, a particular technique (called the Indexed Sequential Method) has
been used since the early 1980s and involves a series of simulations, each applying a
different future inflow scenario (USBR, 1985; Ouarda, et al., 1997). Each future inflow
scenario is generated from the historical natural flow record by “cycling” through that
record. For example, the first simulation assumes that the inflows for 2002 through
2050 will be the 1906 through 1954 record, the second simulation assumes the inflows
for 2002 through 2050 will be the 1907 through 1955 record, and so on. As the method
progresses, the historical record is assumed to “wrap-around” (i.e., after 1990, the
record reverts back to 1906), yielding a possible 85 different inflow scenarios. The

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result of the Indexed Sequential Method is a set of 85 separate simulations (referred to
as “traces”) for each operating criterion that is analyzed. This enables an evaluation of
the respective criteria over a broad range of possible future hydrologic conditions using
standard statistical techniques, discussed in Section 3.3.3.6.
3.3.3.6 POST-PROCESSING AND DATA INTERPRETATION PROCEDURES
The various environmental and socioeconomic analyses in this FEIS required the
sorting and arranging of various types of model output data into tabulations or plots of
specific operational conditions, or parameters, at various points on the system. This
was done through the use of statistical methods and other numerical analyses.
The model generates data on a monthly time step for some 300 points (or nodes) on the
river system. Furthermore, through the use of the Indexed Sequential Method, the
model generates 85 possible outcomes for each node for each month over the time
period 2002 through 2050. These very large data sets are generated for each surplus
alternative and baseline conditions and can be visualized as three-dimensional data
“cubes” with the axes of time, space (or node) and trace (or outcome for each future
hydrology). The data are typically aggregated to reduce the volume of data and to
facilitate comparing the alternatives to baseline conditions and to each or
eri other. The type
of aggregation varies depending upon the needs of the particularInt
resource analysis. The
017
f the categories: those that
post-processing techniques used for this FEIS fall ept.two basic29, 2
into o
.D
ber
aggregate in time, space or both, and those that aggregate the 85 possible outcomes.
vem
ion v
t
o

N
Na
vajo simpleed on
For aggregation in time anda
in N space, rchiv techniques are employed. For example,
ited River 64, ato all California diversion nodes in the model are
c
deliveries of Colorado -168 water
summed to produce14 total delivery to the state for each calendar year. Similarly, lake
No. the
elevations may be chosen on an annual basis (i.e., end of December) to show long-term
lake level trends as opposed to short-term fluctuations. Since the interim criteria period
is 2002 through 2016, some analyses may suggest aggregating over that period of time
and comparing the aggregation over the remaining years (2017 through 2050). The
particular aggregation used will be noted in the methodology section for each resource.

Once the appropriate temporal and spatial aggregation is chosen, standard statistical
techniques are used to analyze the 85 possible outcomes for a fixed time. Statistics that
may be generated include the mean and standard deviation. However, the most
common technique simply ranks the outcomes at each time (from highest to lowest) and
uses the ranked outcomes to compute other statistics of interest. For example, if end-ofcalendar year Lake Mead elevations are ranked for each year, the median outcome for a
given year is the elevation for which half of the values are below and half are above (the
median value or the 50th percentile value). Similarly, the elevation for which 10 percent
of the values are less than or equal to, is the 10th percentile outcome.
Several presentations of the ranked data are then possible. A graph (or table) may be
produced that compares the 90th percentile, 50th percentile, and 10th percentile outcomes

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from 2002 through 2050 for the baseline and all alternatives. It should be noted that a
statistic such as the 10th percentile is not the result of any one hydrologic trace (i.e., no
historical sequence produced the 10th percentile).
3.3.4

MODELING RESULTS

This section presents general and specific discussions of the Colorado River System
operation modeling results. The following sequence of topics is used to address the
potentially affected river system components:
•

Lake Powell water levels,

•

River flows between Glen Canyon Dam and Lake Mead,

•

Lake Mead water levels, and

•

River flows below Hoover Dam.

As noted previously, the potentially affected portion of the Colorado River system
extends from Lake Powell to the SIB. Although lakes Mohave and Havasu are within
the potentially affected area, it has been determined that the interim surplus criteria
ior
would have no effect on the operation of these facilities. The operation of lakes
Inter 17
Mohave and Havasu is pursuant to monthly operating . of the
that
t target elevations 0 are used to
29, 2
manage the storage and release of water and v. Dep
power productionrat these facilities. Under
mbe
the respective target elevations, the Natiolevel n Nove is approximately 14 feet for
water n fluctuation
vajo feet d Lake Havasu. Under all future operating
Lake Mohave and approximately fourhiveforo
c
in Na 4FEIS, lakes Mohave and Havasu would continue to be
scenarios considered under 86 , ar
cited 16 this
operated under the current respective monthly target elevations.
. 14-

No

3.3.4.1 GENERAL OBSERVATIONS CONCERNING MODELING RESULTS
Some changes to the modeling assumptions were anticipated in the DEIS and were
made for the FEIS as noted in Section 3.3.3.3. These changes included the following:
•

updating the initial conditions to reflect the current state of the system;

•

updating the depletion schedules for all of the Basin States, including the
Indian tribes;

•

changing the baseline operation from 75R to 70R (as described in Section
2.2.5); and

•

updating the shortage protection triggers to incorporate the new Upper Basin
depletion schedules.

The general effects of these changes are described below:
•

For the DEIS, the simulation model was run from 2000 through 2050, using
the historical reservoir contents as of January 1, 2000, for the initial

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conditions. For the FEIS, the model was run from 2002 through 2050, using
forecasted reservoir contents for January 1, 2002. The forecast was obtained
from Reclamation’s operations model (the “24-month Study Model”), run in
September, 2000. Due to the relatively low inflow observed for the 2000
water year (approximately 75 percent of normal or about 11.4 maf of natural
inflow to Lake Powell), the total initial system storage decreased
approximately 4.129 maf. This amounted to decreases in initial elevations of
3.5 feet and 26.0 feet at lakes Powell and Mead, respectively. The change in
initial conditions affects the results of the first few years of the simulations,
and then is negligible (after about 2005).
•

Upper Division depletion schedules were updated to those submitted by the
Upper Colorado River Commission (December, 1999), and subsequently
modified to include updated Indian tribes schedules as provided by the Ten
Tribes Partnership. The updated depletion schedules for the Indian Tribes and
the Upper Division totals are detailed in Attachments “Q” and “K”. The total
increase in Upper Division scheduled depletions ranged from two to eight
percent in any given year, with an average over all years of about five percent.
The largest increases are in the early years (eight percent increases in years
2005 through 2010; 6.6 percent in 2016). In general, lakes Powell and Mead
rior baseline
Int under 7
show a more rapid decline (observed in the 50th percentilee
1
the
conditions) due to the increased demand eptheof
in t. early years., 20
r 29 Recovery of Lake
Powell after the interim periodion v. more rapid ase increased depletions
is also D
mb
ov 602(a)the
at
Nthe e
N
tend to turn off equalization earlier due to
storage provision. The
on
vajo
Nathesearchived is that lakes Mead and Powell stabilize at
long-term d in of
effect
, depletions
e
2050 cit 12.56865.5 feet, respectively, below the levels shown in the
about -1 and 4
4
DEIS. o. 1
N

•

Lower Division normal depletion schedules were updated to incorporate the
new Indian tribe demands and remain at each states’ apportionment. Surplus
depletion schedules were also updated for each alternative as provided by the
entities involved and is detailed in Attachment H. The California alternative
tends to be more liberal in the FEIS compared to the DEIS with regard to
surplus deliveries and is now closer to the results of the Shortage Protection
Alternative.

•

As discussed in Section 2.2.5, the baseline surplus strategy was changed from
75R to 70R, which changes the inflow assumption used when computing the
system space available. As discussed in the DEIS, the change has a negligible
effect upon the baseline results.

•

The shortage protection triggers were re-computed to account for the new
Upper Basin depletion schedules and to investigate the issues of protecting a
specified lake level with a specified degree of assurance. To ensure statistical
independence, stochastically generated natural inflows above Powell were
used in the study. The study used the CRSSez model and the procedure is

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documented in the CRSSez User’s Manual (USBR, May 1988). The new
triggers resulted in approximately 73 percent assurance of protecting Lake
Mead elevation 1083 through the year 2040, although after 2040, the
assurance level tails off rapidly (to less than 60 percent in 2050). The validity
of the comparisons between surplus alternatives, however, is not compromised
since all of the modeled conditions use the same shortage protection
assumptions.
The following general observations apply to the overall modeling and analyses results:
•

Future water levels of Lakes Powell and Mead will probably be lower than
historical levels due to increasing Upper Basin depletions under the baseline
conditions and the surplus alternatives. Of the five surplus alternatives, the
Flood Control Alternative and baseline conditions were shown to have the
least tendency to reduce reservoir water levels. The Shortage Protection and
California alternatives were shown to have the highest tendency to reduce
reservoir water levels. The results of the Six States and Basin States
alternatives are similar and fall between those of the baseline conditions and
the Shortage Protection and California alternatives.

•

Median Lake Mead elevations decline throughout the periodiofr analysis for the
ter o
baseline conditions and the surplus alternatives because Lower 17
he In 20 Division
of t
9,
depletions exceed long-term inflow. .Median. Lake Powell elevations decline
ept
D
ber 2
v
vem
for a number of years and thenion
Nat stabilize forothe baseline conditions as well as
n N in Lake Powell elevations for the
all surplus alternatives.jo
va The declining trend
ed o
in Na and allrchiv alternatives is due to increasing Upper
a surplus
baselineted
ci conditions 64, the Six State, Basin States, California, and Shortage
168 For
Division depletions.
14No.
Protection alternatives, the decline is more pronounced due to Lower Basin
surplus deliveries and associated equalization releases from Lake Powell.
Lake Powell elevations eventually stabilize under the baseline conditions and
all alternatives. This behavior is caused by less frequent equalization releases
from Lake Powell (due to the 602(a) storage requirement) as the Upper
Division states continue to increase their use of Colorado River water.

•

A comparative analysis of the baseline conditions with and without California
intrastate transfers was conducted to assess the differences between these two
modeled conditions. The modeling of the two baseline conditions yielded
similar results with two exceptions. The first difference was in the water
deliveries to the individual California agencies participating in the water
transfers. The second difference is reduced river flow (about 200,000 to
300,000 afy) below Parker Dam associated with change in delivery points
resulting from the water transfers. A summary of this comparative analysis is
presented in Attachment L.

•

To test the sensitivity of the results to the use of a 1083-foot shortage
protection level, model runs were also conducted with a protection level of

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1050 feet msl. With the 1050-foot protection level, the water levels on Lake
Mead in 2016 were essentially the same under the baseline condition and
Flood Control Alternative; between 10 and 20 feet lower for the Shortage
Protection and California alternatives; and intermediate for the Six State
Alternative. Water level plots for reservoir levels using the 1050-foot Lake
Mead protection level are in Attachment M.
•

Interim surplus criteria had no effect on Upper Basin deliveries as expected,
including the Indian demands above Lake Powell. As noted in Section
3.4.4.4, the normal delivery schedules of all Upper Basin diversions would be
met under most water supply conditions. Only under periods of low
hydrologic inflow conditions and inadequate regulating reservoir storage
capacity upstream of the diversion point, would an Upper Basin diversion be
shorted. Although the model is not presently configured to track the relative
priorities under those conditions, such effects are identical under baseline and
all alternatives.

•

Under normal conditions, deliveries to the Lower Basin users are always equal
to the normal depletion schedules, including those for the Indian tribes. Under
shortage conditions, only CAP and SNWA share in the shortage until CAP
ior
Inter runs done for
goes to zero (which was not observed in any of thehe
f t modeling 017
,
pt. oPartnership 2 the Lower Basin
this FEIS). Therefore, all tribes in the DeTribe ber 29 in
. 10 em
nv
receive their scheduled depletion, with the ov
Natio d on N exception of the Cocopah Tribe
which has some Arizona Priority 4 water (see Section 3.14.2). As discussed
vajo
e
in Na 4, archiv all Arizona shortages were assigned to CAP
above, itea modeling assumption,
as d
6
c
for this FEIS.-168
14

No.

3.3.4.2 LAKE POWELL WATER LEVELS
3.3.4.2.1 Dam and Reservoir Configuration
Glen Canyon Dam is a concrete arch dam rising approximately 700 feet above the level of
the Colorado River streambed. A profile of the dam is depicted on Figure 3.3-3. Except
during flood conditions, the "full reservoir" water level is 3700 feet msl, corresponding to
the top of the spillway gates. Under normal operating conditions, releases from Glen
Canyon Dam are made through the Glen Canyon Powerplant by means of gates on the
upstream face of the dam. The minimum water level at which hydropower can be
generated is elevation 3490 feet msl. Releases in excess of the powerplant capacity may
be made when flood conditions are caused by high runoff in the Colorado River Basin, or
when needed to provide Beach/Habitat Building Flows (BHBF) downstream of the dam,
as is discussed in Section 3.6.

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Figure 3.3-3
Lake Powell and Glen Canyon Dam Important Operating Elevations

Elevation (feet msl)

3800
3600
3400
3200
3000

ior
Inter 17
e
of th 29 0
pt.operate from , 2
Glen Canyon Dam and Lake Powell were designed to
. De
ber a normal maximum
iona v Novem
water surface elevation of 3700 feet msl to minimum elevation of 3490 feet msl, the
Nat d on
vajo
minimum for hydropower production.hDuring flood conditions, the water surface
ive
Na
d in can64, arc3700 feet msl by raising the spillway radial gates.
elevation of Lakete
ci Powell 8 exceed
Since first reaching 14-16
equalization storage with Lake Mead in 1974, the reservoir water
No.
level has fluctuated from a high of 3708 feet msl to a low of approximately 3612 feet
3.3.4.2.2 Historic Water Levels

msl, as shown on Figure 3.3-4.
3.3.4.2.3 Baseline Conditions
Under the baseline conditions, the water surface elevation of Lake Powell is projected
to fluctuate between full level and decreasingly lower levels during the period of
analysis (2002 to 2050). Figure 3.3-5 illustrates the range of water levels by three lines,
labeled 90th Percentile, 50th Percentile and 10th Percentile. The 50th percentile line
shows the median water level for each future year. The median water level under
baseline conditions is shown to decline to approximately 3663 feet msl by 2019 and
remaining at this or slightly higher levels through 2050. The 10th percentile line shows
there is a 10 percent probability that the water level would drop to 3615 feet msl by 2016
and to 3553 feet msl by 2050. Generally, there is about a 20-foot difference between the
annual high and low water levels at Lake Powell. It should also be noted that the Lake
Powell elevations depicted in Figures 3.3-5 to 3.3-8 are for modeled lake water levels at
the end-of-July. The Lake Powell water level generally reaches its seasonal high in July
whereas the seasonal lows occur at the end of the year.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-19

3380
1960

3420

3460

3500

3540

3580

3620

3660

3700

3740

1965

Figure 3.3-4
Historic Lake Powell Water Levels

1970

1975

3.3-20

Year

1980

1985

1990

Annual Low W ater Level

Annual High W ater Level

1995

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in Minimum4, arc Pool (3490')
cite 1686 Rated Power
o. 14
N

Top of Spillway (3700')

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2000

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3500
2000

3520

3540

3560

3580

3600

3620

3640

3660

3680

3700

3720

2005

90th Percentile

2010

2015

2020

3.3-21

Year

2025

2030

2035

Trace 20

2040

2045

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
Trace 77
ajo N ived
v
in Na 4, arch
cited 1686
10th Percentile
Trace 47 . 14
o
N

50th Percentile

Figure 3.3-5
Lake Powell End-of-July Water Elevations Under Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values and Representative Traces

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

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CHAPTER 3

Three distinct traces were added to Figure 3.3-5 to illustrate what was actually
simulated under the various traces and respective hydrologic sequences and to highlight
that the 90th, 50th and 10th percentile lines do not represent actual traces, but rather the
ranking of the data from the 85 traces for the conditions modeled. The traces also
illustrate the variability among the different traces and that the reservoir levels could
temporarily decline below the 10th percentile line. The trace identified as Trace 20
represents the hydrologic sequence that begins in year 1926. The trace identified as
Trace 47 represents the hydrologic sequence that begins in year 1953. The trace
identified as Trace 77 represents the hydrologic sequence that begins in year 1983.
In Figure 3.3-5, the 90th and 10th percentile lines bracket the range where 80 percent of the
water levels simulated for the baseline conditions occur. The highs and lows shown on the
three traces would likely be temporary conditions. The reservoir level would tend to
fluctuate in the range through multi-year periods of above average and below average
inflows. Neither the timing of water level variations between the highs and the lows, nor
the length of time the water level would remain high or low can be predicted. These
events would depend on the future variation in basin runoff conditions.
Figure 3.3-6 presents a comparison of the 90th, 50th and 10th percentile lines obtained for
the baseline conditions to those obtained for the surplus alternatives. erior
t This figure is best
Intrends that result from
used for comparing the relative differences in the general lakehe
f t level 2017
pt. o er
the simulation of the baseline conditions and surplus alternatives. 29,
De

b
v.
tion n Novem
aControl Alternative is the alternative that could
As illustrated in Figure 3.3-6, vajo N
a the Flood ved o
potentially result in thein N LakerPowell water levels. The Shortage Protection
highest , a chi
ted 68 Alternative are the alternatives that could potentially result
4
Alternative andci California6
the
4-1
1
in the lowest water. levels. The baseline conditions yield similar levels to those observed
No
under the Flood Control Alternative. The water levels observed under the California
alternative are similar to those observed under the Shortage Protective Alternative. The
results obtained under the Six States and Basin States alternatives are similar and fall
between the Baseline and Shortage Protection alternatives.

Figure 3.3-7 shows the frequency that future Lake Powell end-of-July water elevations
would exceed elevation 3695 feet msl under the baseline conditions and surplus
alternatives. When the Lake Powell water level is at or exceeds 3695 feet msl, the
reservoir is considered to be essentially full. In year 2016, under baseline conditions,
the percentage of values greater than or equal to elevation 3695 feet msl is 27 percent.
In 2050, the percentage of values greater than or equal to elevation 3695 feet msl is 26
percent.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-22

3500
2000

3520

3540

3560

3580

3600

3620

3640

3660

3680

3700

3720
90th Percentile

2005

2010

2015

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

2020

3.3-23

Year

2025

2030

2035

2040

2045

50th
ior Percentile
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
10th Percentile
cite 168
14
No.
Baseline Conditions

Figure 3.3-6
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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0%
2000

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2005

2010

2015

2020

3.3-24

Year

2025

2030

2035

2040

2045

Shortage Protection Alternative

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.3-7
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 3695 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

Figure 3.3-8 provides a comparison of the frequency that future Lake Powell end-of-July
water elevations under baseline conditions and the surplus alternatives would be at or
exceed a lake water elevation of 3612 feet msl. Lake Powell water surface elevation 3612
feet msl is used in this analysis as the low threshold elevation for marina and boat ramps at
Lake Powell. This threshold elevation of 3612 feet msl is used to evaluate the baseline
conditions and the effects of interim surplus criteria alternatives on shoreline facilities at
Lake Powell in the Environmental Consequences section (Section 3.9.2.3.1). The lines
represent the percentage of values greater than or equal to the lake water elevation of 3612
feet msl under the baseline conditions and surplus alternatives. In year 2016, under the
baseline conditions, the percentage of values greater than or equal to elevation 3612 feet
msl is 91 percent. In 2050, the percentage of values greater than or equal to elevation 3612
feet msl decreases to 72 percent for the baseline conditions.
3.3.4.2.4 Comparison of Surplus Alternatives to Baseline Conditions
Figure 3.3-6 compared the 90th, 50th and 10th percentile water levels of the surplus
alternatives to those of the baseline conditions. As discussed above, under baseline
conditions, future Lake Powell water levels at the upper and lower 10th percentiles
would likely be temporary and the water level would fluctuate between them in
response to multi-year variations in basin runoff conditions. The sameor
i would apply to
th
th
Inter and 10th
all the surplus alternatives. The 90 percentile, median (50thpercentile) 17
0
f e
pt. o er 2 of 2
percentile values of the surplus alternatives are compared to those 9, the baseline
e
.D
b
conditions in Table 3.3-4. The valuesation v in this em include those for years
presented
Nov table
o N ed on
2016 and 2050 only.
avaj
v

in N
rchi
ited 6864, a Table 3.3-4
c
-1
Elevations
o. 14 Lake Powell End-of-July Water Baseline Conditions
N Comparison of Surplus Alternatives and
th

th

th

90 , 50 and 10 Percentile Values
Year 2016
Alternative
Baseline Conditions
Basin States
Flood Control
Six States
California
Shortage Protection

Year 2050

90th
Percentile

50th
Percentile

10th
Percentile

90th
Percentile

50th
Percentile

10th
Percentile

3699
3699
3699
3699
3699
3699

3665
3664
3665
3664
3660
3659

3615
3603
3615
3603
3595
3594

3699
3699
3699
3699
3699
3699

3663
3663
3665
3663
3663
3663

3553
3551
3553
3551
3551
3551

Figure 3.3-7 compared the percentage of Lake Powell elevations that exceeded
3695 feet msl for the surplus alternatives and baseline conditions. Table 3.3-5 provides
a summary of that comparison for years 2016 and 2050.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-25

70%
2000

75%

80%

85%

90%

95%

100%

2005

2010

2015

2020

3.3-26

Year

2025

2030

2035

2040

Six States Alternative

2045

ior
Inter 17
California Alternative
the
ofShortage Protection20
9, Alternative
pt.
. De ember 2
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.3-8
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 3612 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Table 3.3-5
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 3695 Feet
Alternative
Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

Year 2016
27%
21%
27%
22%
18%
18%

Year 2050
26%
26%
26%
26%
26%
26%

Figure 3.3-8 compared the percentage of Lake Powell elevations that exceeded
3612 feet msl for the surplus alternatives and baseline conditions. Table 3.3-6 provides
a summary of that comparison for years 2016 and 2050.
Table 3.3-6
Lake Powell End-of-July Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 3612 Feet

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.
3.3.4.3 RIVER FLOWS BETWEEN LAKE POWELL AND LAKE MEAD
Alternative
Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

Year 2016
91%
88%
91%
88%
87%
86%

Year 2050
72%
72%
72%
72%
72%
72%

The river flows between Glen Canyon Dam and Lake Mead result from controlled
releases from Glen Canyon Dam (Lake Powell) and include gains from tributaries in
this reach of the river. Releases from Glen Canyon Dam are managed as previously
discussed in Sections 3.2.1.2 and 3.3.1.1. The most significant gains from perennial
streams include inflow from the Little Colorado River and Paria River. However,
inflow from these streams is concentrated over very short periods of time, and on
average, make up approximately two percent of the total annual flow in this reach of the
river.
Figure 3.3-9 provides a comparison of the relative frequency of occurrence of annual
releases from Lake Powell under the baseline conditions and surplus alternatives, during
the interim surplus criteria period (through 2016). Releases between 8.23 and 11.5 maf
generally correspond to years where equalization releases are being made from Lake
Powell. The surplus water deliveries from Lake Mead associated with the interim
surplus criteria tend to increase the relative frequency of equalization during that period
compared to baseline conditions.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-27

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

8.23 maf

8.23 to 10 maf

10 to 11.5 maf

3.3-28

Amount Released

11.5 to 13 maf

13-14.5 maf

14.5-16 maf

>16 maf

Shortageor
i Protection Alternative
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.3-9
Histogram of Modeled Lake Powell Annual Releases (Water Years)
2002 to 2016 (85 Traces)

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Frequency of Occurrences

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

3.3.4.4 LAKE MEAD WATER LEVELS
This section provides a general description of Hoover Dam and Lake Mead, discusses
historic Lake Mead water levels and summarizes the results of the future Lake Mead
water level simulations under baseline conditions and the surplus alternatives.
3.3.4.4.1 Dam and Reservoir Configuration
Hoover Dam and Lake Mead are operated with the following three main priorities:
1) river regulation, improvement of navigation, and flood control, 2) irrigation and
domestic uses, including the satisfaction of present perfected water rights, and 3) power.
The Boulder Canyon Project Act of 1928 specified flood control as the project purpose
having first priority for operation of Hoover Dam and Lake Mead.
Hoover Dam is the northernmost Reclamation facility on the lower Colorado River and
is located 326 miles downstream of Lee Ferry. Hoover Dam provides flood control
protection and Lake Mead provides the majority of the storage capacity for the Lower
Basin as well as significant recreation opportunities. Lake Mead storage capacity is
27.38 maf at a maximum water surface elevation of 1229.0 feet msl. At this elevation,
Lake Mead’s water surface area would equal 163,000 acres. The dam’s r
rio four intake
towers draw water from the reservoir at elevations above 895 e Into drive 7 generators
feet te
17
h
. of t r 29, 201
within the dam’s powerplant. The minimum water surface elevation for effective power
t
Dep mbe
generation is 1083 feet msl.
n v.
ve
io

Nat d n No
vajo Meadvwereoestablished to manage potential flood
Flood control regulationsNa Lake rchi e
in for 4, a
ited and snowmelt. Lake Mead’s uppermost 1.5 maf of storage
c
events arising from rain 686
-1
capacity, between .elevations 1219.61 and 1229.0 feet, is defined as exclusive flood
o 14
N

control. Within this capacity allocation, 1.218 maf of flood storage is above elevation
1221.0 feet, the top of the raised spillway gates. Figure 3.3-10 illustrates some of the
important Hoover Dam and Lake Mead water surface elevations that are referenced in
subsequent sections.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-29

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Figure 3.3-10
Lake Mead and Hoover Dam Important Operating Elevations

INTAKE TOWERS

1400

TOP OF DAM EL. 1232
SPILLWAY

Elevation (feet msl)

1200
POWER HOUSE

1000
800
PENSTOCK

600
400

ior
Inter 17
f the 9 0
pt. o erand , 2
Lake Mead usually is at its maximum water level in November 2 December. If
. De
b
o achieved between
iis n v Novem August 1 to January 1.
at
required, system storage space-building
on
jo N
Hoover Dam storage space-building chived are limited to 28,000 cfs, while the mean
Nava ar releases
in
daily releases to imeet the water delivery orders of Colorado River water entitlement
c ted 16864,
holders normally range-between 8000 cfs to 18,000 cfs.
14
No.
In addition to controlled releases from Lake Mead to meet water supply and power
requirements, water is also diverted from Lake Mead at the SNWA Saddle Island intake
facilities, Boulder City’s Hoover Dam intake, and the Basic Management, Inc.’s (BMI)
intake facility for use in the Las Vegas area for domestic purposes by SNWA, BMI and
other users.
The diversions by SNWA at its Saddle Island intake facilities entail pumping the water
from the intake to SNWA’s transmission facilities for treatment and further conveyance
to the Las Vegas area. The elevation of the original SNWA intake is approximately
1000 feet msl. However, the minimum required Lake Mead water level necessary to
operate the pumping units at SNWA’s original intake facility is 1050 feet msl. SNWA
recently constructed a second pumping plant with an intake elevation of 950 feet msl.
The minimum required Lake Mead water level necessary to operate the pumping units
at SNWA’s second intake facility is 1000 feet msl. The new SNWA intake provides
only a portion of the capacity required by SNWA to meet its Lake Mead water supply
needs. Therefore, the intake elevation of SNWA’s original pumping plant is critical to
its ability to divert its full Colorado River water entitlement.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-30

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

3.3.4.4.2 Historic Lake Mead Water Levels
Figure 3.3-11 presents an overview of the historic annual water levels (annual
maximum and minimum) of Lake Mead. As noted in Figure 3.3-11, the annual change
in elevations of Lake Mead has ranged from less than ten feet to as much as 75 feet msl.
The decrease in the range of the elevations within a year observed after the mid-1960s
can be attributed to the regulation provided by Lake Powell.
Historic Lake Mead low water levels have dropped to the minimum rated power
elevation (1083 feet msl) of the Hoover Powerplant during two periods (1954 to 1957
and 1965 to 1966). The maximum Lake Mead water surface elevation of approximately
1225.6 feet msl occurred once, in 1983.
Three Lake Mead water surface elevations of interest are shown in Figure 3.3-11. The
first elevation is 1221 feet msl, the top of the spillway gates. The second elevation is
1083 feet msl, the minimum elevation for the effective generation of power. The third
elevation is 1050 feet msl, the minimum elevation required for the operation of
SNWA’s original intake facility.

ior
Inter 17
f the
Under the baseline conditions, the water surface elevation of Lake9, 20 is projected to
pt. o er 2 Mead
e
b
fluctuate between full level and decreasinglyv. D levels during the period of analysis
lower
ion rangeNovem levels (end of December)
at the on of water
(2002 to 2050). Figure 3.3-12 illustrates
jo N
d
Nava arc 50th Percentile and 10th Percentile. The 50th
by three lines, labeled i90th Percentile, hive
n
d the median, water level for each future year. The median water
cite 16864
percentile line shows
level under baseline14
is
No. conditionsth shown to decline to 1162 feet msl by 2016 and to
3.3.4.4.3 Baseline Conditions

1111 feet msl by 2050. The 10 percentile line shows there is a 10 percent probability
that the water level would decline to 1093 feet msl by 2016 and to 1010 feet msl by 2050.
It should also be noted that the Lake Mead elevations depicted in Figure 3.3-12
represent water levels at the end of December which is when lake levels are at a
seasonal high. Conversely, the Lake Mead water level generally reaches its annual low
in July.
Three distinct traces are added to Figure 3.3-12 to illustrate what was actually simulated
under the various traces and respective hydrologic sequences and to highlight that the
90th, 50th and 10th percentile lines do not represent actual traces, but rather the ranking
of the data from the 85 traces for the conditions modeled. The three traces illustrate the
variability among the different traces and that the reservoir levels could temporarily
decline below the 10th percentile line. The trace identified as Trace 20 represents the
hydrologic sequence that begins in year 1926. The trace identified as Trace 47
represents the hydrologic sequence that begins in year 1953. The trace identified as
Trace 77 represents the hydrologic sequence that begins in year 1983.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-31

660

700

740

780

820

860

900

940

980

1020

1060

1100

1140

1180

1220

1260

1935

1940

1945

1950

1955

1960

1970
Year

3.3-32

1965

1975

1980

1985

1990

Minimum SNWA Intake Elevation (1050')

Minimum Rated Power Pool (1083')

Top of Spillway (1221')

Figure 3.3-11
Historic Lake Mead Water Levels
(Annual Highs and Lows)

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc Annual High Water Level
cite 168
Annual Low Water Level
o. 14
N

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

1995

2000

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1000
2000

1020

1040

1060

1080

1100

1120

1140

1160

1180

1200

1220

1240
90th Percentile

2005

2010

2015

2020

3.3-33

Year

2025

2030

2035

2040

2045

ior
Inter 17 Trace 77
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
10th Percentile
cite 168
Trace 47Trace 20
o. 14
N
50th Percentile

Figure 3.3-12
Lake Mead End-of-December Water Elevations Under Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values and Representative Traces

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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CHAPTER 3

In Figure 3.3-12, the 90th and 10th percentile lines bracket the range where 80 percent of
future Lake Mead water levels simulated for the baseline conditions occur. The highs and
lows shown on the three traces would likely be temporary conditions. The reservoir level
would tend to fluctuate through multi-year periods of above average and below average
inflows. Neither the timing of water level variations between the highs and the lows, nor
the length of time the water level would remain high or low can be predicted. These
events would depend on the future variation in basin runoff conditions.
Figure 3.3-13 presents a comparison of the 90th, 50th and 10th percentile lines obtained for
the baseline conditions to those obtained for the surplus alternatives. This figure is best
used for comparing the relative differences in the general lake level trends that result from
the simulation of the baseline conditions and surplus alternatives.
As illustrated in Figure 3.3-13, the Flood Control Alternative is the alternative that could
potentially result in the highest Lake Mead water levels. The California Alternative is the
alternative that could potentially result in the lowest water levels. The water levels
observed under the Shortage Protection Alternative are similar to those of the California
Alternative with some years slightly lower. The baseline conditions yield slightly lower
levels than the Flood Control Alternative, but the differences are very small. The results
obtained under the Six States and Basin States alternatives are similarerior between the
and fall
Int
Flood Control and Shortage Protection alternatives.
017
f the

pt. o
29, 2
. De that mberLake Mead end of
Figure 3.3-14 provides a comparison of the n v
frequency e future
N
Natioconditions ov the surplus alternatives would be
December water elevations under o
vaj baseline ed on and
v
at or exceed a lake water elevation archi feet msl. The lines represent the percentage of
of 1200
in Na
ited equal 864, lake water elevation of 1200 feet msl under the baseline
c
values greater than or -16 to the
4
conditions andNo. 1 alternatives. In year 2016, under the baseline conditions, the
surplus
percentage of values greater than or equal to elevation 1200 feet msl is 22 percent. In
2050, the percentage of values greater than or equal to elevation 1200 feet msl decreases to
14 percent for the baseline conditions.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-34

1000
2000

1020

1040

1060

1080

1100

1120

1140

1160

1180

1200

1220

2005

2010

2015

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

2020

3.3-35

Year

2025

2030

2035

2040

10th Percentile

ior
Inter 17
e
of th 29, 20
pt.
. De ember 50th Percentile
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

2045

90th Percentile

Figure 3.3-13
Lake Mead End-of-December Water Elevations
th
th
th
Comparison of Surplus Alternatives and Baseline Conditions 90 , 50 and 10 Percentile Values

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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0%
2000

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

2005

2010

2015

2020

3.3-36

Year

2025

2030

2035

2040

2045

California Alternative

r
terio
InShortage Protection Alternative
e
of th 29, 2017
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

3.3-14
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1200 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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CHAPTER 3

Figure 3.3-15 provides a comparison of the frequency that future Lake Mead end of
December water elevations would be at or exceed a lake water elevation of 1083 feet
msl under baseline conditions and the surplus alternatives. In year 2016, under the
baseline conditions, the percentage of values greater than or equal to elevation 1083 feet
msl is 93 percent. In 2050, the percentage of values greater than or equal to elevation
1083 feet msl decreases to 58 percent for the baseline conditions.
Figure 3.3-16 provides a comparison of the frequency that future Lake Mead end of
December water elevations under baseline conditions and the surplus alternatives would
be at or exceed a lake water elevation of 1050 feet msl. In year 2016, under the baseline
conditions, the percentage of values greater than or equal to elevation 1050 feet msl is 100
percent. In 2050, the percentage of values greater than or equal to elevation 1050 feet msl
decreases to 75 percent for the baseline conditions.
Figure 3.3-17 provides a comparison of the frequency that future Lake Mead end of
December water elevations under baseline conditions and the surplus alternatives would
be at or exceed a lake water elevation of 1000 feet msl. In year 2016, under the baseline
conditions, the percentage of values greater than or equal to elevation 1000 feet msl is 100
percent. In 2050, the percentage of values greater than or equal to elevation 1000 feet msl
decreases to 99 percent for the baseline conditions.
erior

Int
f the 9, 2017
3.3.4.4.4 Comparison of Surplus Alternatives topt. o
Baseline Conditions
2
v De vember
n th .
tio
o
th
Figure 3.3-13 compared the 90ajo Na 10 on N
, 50th and d percentile water levels of the surplus
v
e
alternatives to thosed in Nbaseline rchiv
of the a
, a conditions. As discussed above, under baseline
ite Mead water levels at the upper and lower 10th percentiles would
c
conditions, future Lake-16864
likely be temporary14 the water levels are expected to fluctuate between them in
No. and
response to multi-year variations in basin runoff conditions. The same would apply to
all the surplus alternatives. The 90th percentile, median (50th percentile) and 10th
percentile values of the surplus alternatives are compared to those of the baseline
conditions in Table 3.3-7. The values presented in this table include those for years
2016 and 2050 only.
Table 3.3-7
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
th
90 , 50th and 10th Percentile Values
Year 2016
Alternative
Baseline Conditions
Basin States
Flood Control
Six States
California
Shortage Protection

Year 2050

90th
Percentile

50th
Percentile

10th
Percentile

90th
Percentile

50th
Percentile

10th
Percentile

1215
1215
1215
1215
1208
1208

1162
1143
1162
1146
1131
1130

1093
1082
1095
1084
1071
1077

1209
1209
1210
1210
1209
1209

1111
1111
1111
1111
1111
1111

1010
1007
1010
1008
1003
1005

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-37

50%
2000

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

2005

2010

2015

2020

3.3-38

Year

2025

2030

2035

2040

2045

California Alternative

r
terio
InShortage Protection Alternative
e
of th 29, 2017
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.3-15
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1083 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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70%
2000

75%

80%

85%

90%

95%

100%

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

2005

2010

2015

2020

3.3-39

Year

2025

2030

2035

2040

2045

2050

CHAPTER 3

California Alternative
r
terio Protection Alternative
In Shortage 7
e
of th 29, 201
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Figure 3.3-16
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1050 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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90%
2000

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

2005

2010

2015

2020

3.3-40

Year

2025

2030

2035

2040

Six States Alternative

Flood Control Alternative

2045

ior
Inter 17
e
0
of th California,Alternative
29 2
ept. beShortage Protection Alternative
r
D
n v.
em
tio
ov
jo Na ved on N
Nava archi
in
cited 16864,
o. 14
N

Basin States Alternative

Baseline Conditions

Figure 3.3-17
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1000 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Figure 3.3-14 compared the percentage of Lake Mead elevations that exceeded
1200 feet msl for the surplus alternatives and baseline conditions. Table 3.3-8 provides
a summary of that comparison for years 2016 and 2050.
Table 3.3-8
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1200 Feet
Alternative
Baseline Conditions
Basin States
Flood Control
Six States
California
Shortage Protection

Year 2016
22%
19%
22%
19%
14%
16%

Year 2050
14%
14%
16%
15%
14%
14%

Figure 3.3-15 compared the percentage of Lake Mead elevations that exceeded
1083 feet msl for the surplus alternatives and baseline conditions. Table 3.3-9 provides
a summary of that comparison for years 2015 and 2050.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation Year 2016 ve
No
Alternative
Year 2050
jo N ved on
Baseline Conditions ava
93%
58%
i
N
h
Basin States in
89%
58%
d
, arc
4
cite
Flood Control -1686
94%
59%
Six States. 14
89%
58%
No
California
87%
59%
Table 3.3-9
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1083 Feet

Shortage Protection

87%

58%

Figure 3.3-16 compared the percentage of Lake Mead elevations that exceeded
1050 feet msl for the surplus alternatives and baseline conditions. Table 3.3-10
provides a summary of that comparison for years 2016 and 2050.
Table 3.3-10
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1050 Feet
Alternative
Baseline Conditions
Basin States
Flood Control
Six States
California
Shortage Protection

Year 2016
100%
99%
100%
99%
95%
98%

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-41

Year 2050
75%
75%
75%
75%
75%
75%

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Figure 3.3-17 compared the percentage of Lake Mead elevations that exceeded
1000 feet msl for the surplus alternatives and baseline conditions. Table 3.3-11
provides a summary of that comparison for years 2016 and 2050.
Table 3.3-11
Lake Mead End-of-December Water Elevations
Comparison of Surplus Alternatives and Baseline Conditions
Percentage of Values Greater than or Equal to Elevation 1000 Feet
Alternative
Baseline Conditions
Basin States
Flood Control
Six States
California
Shortage Protection

Year 2016
100%
100%
100%
100%
100%
100%

Year 2050
99%
99%
99%
99%
92%
99%

3.3.4.5 COMPARISON OF RIVER FLOWS BELOW HOOVER DAM
This section describes results of the analysis of the simulated Colorado River flows
below Hoover Dam. The model of the Colorado River system was used to simulate
future mean monthly flows under baseline conditions and the surplusralternatives. Four
ior
Inte river reaches
specific river locations were selected to represent flows within selected017
f the
below Hoover Dam. The river reaches and corresponding flow locations are listed in
pt. o er 29, 2
. De
Table 3.3-12 and are shown graphically ion Map 3.3-1. emb
on v
ov
at

N
N
vajo hived on
Na
d in 64, arc Table 3.3-12
iteColorado8River Flow Locations Identified for Evaluation
c
-16
o. 14
Selected River Flow Locations
N
Colorado River Reach
Description

ween Hoover Dam and Parker Dam
ween Parker Dam and Palo Verde Diversion
Dam
ween Palo Verde Diversion and Imperial Dam
ween Imperial Dam and SIB
1

vasu National Wildlife Refuge (NWR)

Approximate
1
River Mile
242.3

stream of Colorado River Indian Reservation

180.8

wnstream of the Palo Verde Diversion Dam
ow the Mexico Diversion at Morelos Dam

133.8
23.1

River miles as measured from the southerly international border with Mexico

Two types of analysis of the potential of interim surplus criteria to affect river flows
were conducted. In the first analysis, the potential effects on the total annual volume of
flow in each reach were evaluated. In this analysis, the mean monthly flows were first
summed over each calendar year. The 90th, 50th, and 10th percentiles of the annual
volumes were then computed for each year. Plots of these percentiles for baseline

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-42

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

conditions and all surplus alternatives are included in this section for each of the four
river points. Cumulative distributions of the annual flow volumes are also presented for
specific years to aid in the understanding of the effects. These cumulative distributions
consider the year 2006, the year when the largest effects at the 90th percentile are seen.
The second analysis investigated the potential effects on seasonal flows. Cumulative
distributions of mean monthly flows (in cfs) were produced for specific years and
selected months representative of each season. The mean monthly flows for January
were used to represent the winter season flows and likewise for April, July, and October
to represent spring, summer, and fall, respectively. The specific years analyzed
included 2006, 2016, 2025, and 2050. Only the graphs for 2016 are presented in this
section. The graphs for the other years are presented in Attachment N.
It should be noted that the monthly demand schedules used in the model are based on a
distribution of the total annual demand (a percentage for each month). Although each
diversion point may use a different distribution, those percentages do not change from
year to year, and can not reflect potential future changes in the system that might affect
the monthly distributions. Therefore, the seasonal differences are primarily governed
by the overall changes in annual flow volumes, coupled with the effect of each
diversion’s distribution upstream of the point of interest.
erior

Int
f the 9, 2017
o
Daily and hourly releases from Hoover Dam reflectpt. short-term demands of Colorado
2
. De theembermanagement in Lakes
nv
River water users with diversions located downstream, storage
atio
Nov
Mohave and Havasu, and powerjo N ved on
a production at Hoover, Davis and Parker Dams. The
av
i
close proximity ofed in Mohave to rch
Lake N 4, a Hoover Dam effectively dampens the short-term
it
c
6 6
fluctuations below Hoover 8
14-1 Dam. The scheduling and subsequent release of water
. Parker Dams create short-term fluctuations in river flows, depths,
through DavisNo
and
and water surface elevations downstream of these structures. These fluctuations of
water surface elevations in the river are most noticeable in the river reaches located
immediately downstream of the dams and lessen as the downstream distance increases.
Interim surplus criteria, however, will have no effect on the short-term operations of
Hoover, Davis and Parker Dam, and therefore, short-term fluctuations in river reaches
downstream of Hoover Dam were not evaluated.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-43

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

Map 3.3-1
Colorado River Locations Selected for Modeling

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-44

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

3.3.4.5.1 River Flows Between Hoover Dam and Parker Dam
The river flows between Hoover Dam and Parker Dam are comprised mainly of flow
releases from Hoover Dam and Davis Dam. Inflows from the Bill Williams River and
other intermittent tributaries are infrequent and are usually concentrated into short time
periods due to their dependence on localized precipitation. Tributary inflows comprise
less than one percent of the total annual flow in this reach of the river.
Due to the backwater effect of Lake Mohave, a point on the Colorado River
downstream of Davis Dam was used to evaluate the river flows for this reach, located
immediately downstream of the Havasu National Wildlife Refuge (NWR).
The 90th, 50th, and 10th percentile annual flow volumes for this reach are shown in
Figure 3.3-18. As shown by the 50th percentile values, annual flow volumes in this
reach can be expected to be greater for the surplus alternatives (except for the Flood
Control Alternative) than for the baseline conditions during the 15-year interim surplus
criteria period. This is a direct result of more frequent surplus deliveries. The largest
increases from baseline conditions occur under the California Alternative and range
from approximately 13 percent in the first two years down to three percent by 2016.
Results for the Six States and Basin States alternatives are similar to rior other, ranging
each
Inte
from approximately a six percent increase over baseline conditions down17 three
to
he
. of t r 29, 20
percent by 2016. Beyond the 15-year interim period,tthe annual flow volumes under the
Dep mbe
surplus alternatives are essentially the same (within ovepercent) as those under the
one
n v.
Natio d on N
baseline conditions.
vajo
e

in Na
rchiv
ited level,864, a the magnitudes of the annual flow volumes are
c
At the 10 percentile -16 although
1
different, the relative 4
No. changes in surplus conditions compared to the baseline conditions
th

are similar to those at the 50th percentile.

At the 90th percentile level, all surplus alternatives (except for the Flood Control
Alternative) show annual flow volumes less than or equal to the flows under the
baseline conditions. This is the result of more frequent surplus deliveries, which tend to
lower Lake Mead reservoir levels. With lower reservoir levels, the frequency of flood
control events (which contribute most of the flows at the 90th percentile level) is
decreased, which in turn decreases the annual flow volume for a given percentile. The
California and Shortage Protection alternatives exhibit the largest decreases, ranging
from approximately 13 percent less than baseline conditions in 2006 to one percent less
by 2023. Results for the Six States and Basin States alternatives are similar to each
other, ranging from approximately six percent less than baseline conditions in 2013 to
one percent less by 2023.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-45

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Figure 3.3-18
Colorado River Downstream of Havasu NWR Annual Flow Volume (af)
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values
90th Percentile
15,000,000

14,000,000
An
nu
al 13,000,000
Flo
w
Vol 12,000,000
um
e
(af) 11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

10,000,000

9,000,000

8,000,000

50th Percentile
15,000,000

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
10,000,000
cited 16864,
149,000,000
No.

14,000,000
An
nu
al 13,000,000
Flo
w
Vol 12,000,000
um
e
(af) 11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

8,000,000

10th Percentile
15,000,000

14,000,000
An
nu
al 13,000,000
Flo
w
Vol 12,000,000
um
e
(af) 11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

10,000,000

9,000,000

8,000,000
2000

2005

2010

2015

2020

2025
Year

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-46

2030

2035

2040

2045

2050

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

In Figure 3.3-19, the cumulative distribution of annual flow volumes is shown for year
2006. This is the year of the largest differences at the 90th percentile level as shown in
Figure 3.3-18. Although the annual flow volumes decrease for all surplus alternatives
(except Flood Control Alternative) at a fixed percentile (i.e. at the 90th percentile) as
compared to baseline, the range of annual flow volumes are the same for baseline
conditions and the surplus alternatives. The frequency that a flow of a specific
magnitude will occur, however, is lower under the surplus alternatives (except for the
Flood Control Alternative) as shown in Figure 3.3-19.
Figures 3.3-20(a-d) present comparisons of the representative seasonal flows under
baseline conditions and the surplus alternatives for 2016. For all seasons, the Flood
Control Alternative is very similar to the baseline conditions. The Six States and Basin
States alternatives tend to fall between the baseline conditions (and Flood Control
Alternative) and the California (and Shortage Protection) alternatives.
As expected, the largest flows occur in the spring and summer seasons for baseline
conditions and all alternatives due to downstream irrigation demands. For flows that
are due primarily to flood control releases from Lake Mead (flows in the 90th – 100th
percentile range), the range of mean monthly flows is not changed by the different
surplus alternatives, since these magnitudes are dictated by the flood rior
control
Inte 17 (except
regulations. These flows occur, however, less often for thethe
surplus alternatives
20
of
the Flood Control Alternative). This effect is less ept.
pronounced r 29, when most flood
in July,
v. D vembe
control releases have ceased.
o
ation

N
N
vajo hived on
The differences in flows that are,not c to flood control releases are greatest near the
in Na 4 r due
ited A numericala
th
c
70 percentile level. -1686
comparison of the 70th percentile values is shown in
4
Table 3.3-13. No. differences in mean monthly flows for the California Alternative
The 1

compared to baseline conditions are approximately 16 percent in the winter, nine
percent in the spring, six percent in the summer, and eight percent in the fall. For the
Basin States alternative, the differences (compared to baseline conditions) in mean
monthly flows are approximately three percent in the winter, one percent in the spring,
and less than one percent in the summer and fall seasons.
Despite these differences, the flows for all alternatives fall well within the minimum
and maximum flows for the baseline conditions, as well as within the current
operational range for this reach.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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Table 3.3-13
Comparison of Mean Monthly Flow (cfs) – Baseline Conditions and Surplus Alternatives
Colorado River Downstream of Havasu NWR (River Mile = 242.3)
th
70 Percentile Values for Year 2016
Mean Monthly Flows (cfs) for Year 2016 at the 70th Percentile
Season
Baseline

Basin States

Flood Control

Six States

California

Shortage
Protection

Winter

8069

8347

7965

8317

9327

9223

Spring

15939

16166

15899

16072

17294

17144

Summer

15880

15957

15862

15953

16853

16644

Fall

11776

11805

11776

11686

12688

12531

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-48

8,000,000

9,000,000

10,000,000

11,000,000

12,000,000

13,000,000

14,000,000

15,000,000

16,000,000

17,000,000

18,000,000

19,000,000

0%

25%

3.3-49

Percent of Values Less than or Equal to

50%

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
Baseline Conditions

90th Percentile

Figure 3.3-19
Colorado River Annual Flow Volume Downstream of Havasu NWR
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Flow Volume (af)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-50

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Winter Season Flows
as Represented by January Flows

Figure 3.3-20a
Colorado River Seasonal Flows Downstream of Havasu NWR
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-51

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Spring Season Flows
as Represented by April Flows

Figure 3.3-20b
Colorado River Seasonal Flows Downstream of Havasu NWR
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-52

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Summer Season Flows
as Represented by July Flows

Figure 3.3-20c
Colorado River Seasonal Flows Downstream of Havasu NWR
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-53

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Fall Season Flows
as Represented by October Flows

Figure 3.3-20d
Colorado River Seasonal Flows Downstream of Havasu NWR
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

3.3.4.5.2 River Flows Between Parker Dam and Palo Verde Diversion
The point on the Colorado used to evaluate the river flows in the reach of the river
located between Parker Dam and the Palo Verde Diversion Dam is located immediately
upstream of the Colorado River Indian Reservation (CRIR) diversion. The CRIR
diversion is located at Headgate Rock Dam, approximately 14 miles below Parker Dam.
Flows in this reach of the river result from primarily from releases from Parker Dam
(Lake Havasu).
Future flows in this reach would be affected by the proposed water transfers and
exchanges between the California agricultural water agencies and MWD, which change
the point of diversion. For example, under a potential transfer between IID and MWD
(or SDCWA), the water that would normally be diverted at Imperial Dam would now be
diverted above Parker Dam. As discussed in Section 3.3.3.2, the proposed California
intrastate transfers are included in the simulation of the baseline conditions and surplus
alternatives. Although the transfers themselves are not a direct result of the proposed
interim surplus criteria, the transfers were modeled because they are expected to be a
component of the future Lower Basin water supply management programs and to
maintain consistency for comparison of the alternatives to baseline conditions. The
r
intrastate transfers proposed by California and any potential environmental effects that
terio and
InNEPA17 other
would occur as a result of those actions are addressed by separate
0
f the
pt. o er 29, 2
environmental compliance.
e
D

v.
mb
ation on Nove this reach are shown in
The 90 , 50 , and 10 percentileo N flow volumes for
vaj annualved
Figure 3.3-21. As shown N the , archi
in bya 450th percentile values, annual flow volumes in this
cited 16 greater for the California and Shortage Protection
reach can be expected to be86
4alternatives thano. 1 baseline conditions and other alternatives during the 15-year
N for the
th

th

th

interim surplus criteria period. This is the result of more frequent surplus deliveries
under those two alternatives. Increases from baseline conditions under the California
Alternative range from approximately seven percent in the first year down to one
percent by 2013. A 1.5 percent decrease from baseline conditions is seen for the period
2017 through 2050 as a result of the modeled transfer of 100 kaf from PVID to MWD
as part of the California Alternative. Increases from baseline conditions under the
Shortage Protection Alternative range from approximately four percent in the first year
down to two percent by 2016. The annual flow volumes for the Flood Control, Six
States, and Basin States alternatives are essentially the same (less than one percent) as
those under the baseline conditions for the entire period of analysis (2002 through
2050).
Similar results are seen at the 10th percentile level. Increases from baseline conditions
under the California Alternative range from approximately six percent in the first year
down to two percent by 2006. A 1.6 percent decrease from baseline conditions is seen
for the period 2017 through 2050 as a result of the modeled transfer of 100 kaf from
PVID to MWD as part of the California Alternative. Increases from baseline conditions
under the Shortage Protection Alternative range from approximately three percent in the

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-54

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

Figure 3.3-21
Colorado River Upstream of CRIR Diversion Annual Flow Volume (af)
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values
90th Percentile
12,000,000

Annual Flow Volume (af)

11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

10,000,000
9,000,000
8,000,000
7,000,000
6,000,000
5,000,000

50th Percentile
12,000,000

ior
Inter 17
10,000,000
0
f the
pt. o er 29, 2
e
v. D
9,000,000
mb
ation on Nove
jo N
8,000,000
Nava archived
in
cited 16864,
7,000,000
14No.
6,000,000

Annual Flow Volume (af)

11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

5,000,000

10th Percentile
12,000,000

Annual Flow Volume (af)

11,000,000
10,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

9,000,000
8,000,000
7,000,000
6,000,000
5,000,000
2000

2005

2010

2015

2020

2025
Year

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-55

2030

2035

2040

2045

2050

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

first year down to one percent by 2016. The annual flow volumes for the Flood
Control, Six States, and Basin States alternatives are essentially the same (less than one
percent) as those under the baseline conditions for the entire period of analysis (2002
through 2050).
At the 90th percentile level, all surplus alternatives (except for the Flood Control
Alternative) show annual flow volumes less than or equal to the flows under the
baseline conditions. This is the result of more frequent surplus deliveries, which tend to
lower Lake Mead reservoir levels. With lower reservoir levels, the frequency of flood
control events (which contribute most of the flows at the 90th percentile level) is
decreased, which in turn decreases the annual flow volume for a given percentile. The
California and Shortage Protection alternatives exhibit the largest decreases, ranging
from two to 20 percent less than baseline conditions from 2002 through 2023, with the
largest differences in 2006 and 2016. The Six States and Basin States alternatives
exhibit similar behavior, ranging from two to 16 percent less than baseline conditions
from 2002 through 2023, with the largest differences in 2016.
In Figure 3.3-22, the cumulative distribution of annual flow volumes is shown for year
2006. This is the year of the largest differences at the 90th percentile level as shown in
Figure 3.3-21. Although the annual flow volumes decrease for all surplus alternatives
ior
th
Inter percentile) as
(except Flood Control Alternative) at a fixed percentile (i.e.hethe 90 017
f t at
pt. o er 29, 2
compared to baseline, the range of annual flow volumes are the same for baseline
. De that b
conditions and the surplus alternatives. tiThe v
on frequency em a flow of a specific
a
Nov
magnitude will occur, however, jis lowerved othe surplus alternatives (except for the
a o N i under n
Nav ar in
Flood Control Alternative) as shownch Figure 3.3-22.
d in
te
4,

ci
1686
. 14No

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-56

6,000,000

7,000,000

8,000,000

9,000,000

10,000,000

11,000,000

12,000,000

13,000,000

14,000,000

15,000,000

16,000,000

0%

25%

3.3-57

Percent of Values Less than or Equal to

50%

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
Baseline Conditions

90th Percentile

Figure 3.3-22
Colorado River Annual Flow Volumes Upstream of Colorado River Indian Reservation
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2006

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Flow Volume (af)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Figures 3.3-23 (a-d) present comparisons of the representative seasonal flows under
baseline conditions and the surplus alternatives for 2016. As expected, the largest flows
occur in the spring and summer seasons for baseline conditions and all alternatives due
to downstream irrigation demands. For flows that are due primarily to flood control
releases from Lake Mead (flows in the 90th – 100th percentile range), the range of mean
monthly flows is not changed by the different surplus alternatives, since these
magnitudes are dictated by the flood control regulations. These flows occur, however,
less often for the surplus alternatives (except the Flood Control Alternative). This effect
is less pronounced in July, when most flood control releases have ceased.
The differences in flows that are not due to flood control releases are similar for all
alternatives and baseline conditions. A numerical comparison of the 70th percentile
values is shown in Table 3.3-14. The differences in mean monthly flows for the
California Alternative compared to baseline conditions are approximately six percent in
the winter, three percent in the spring, one percent in the summer, and less than one
percent in the fall. For the Basin States alternative, the differences (compared to
baseline conditions) in mean monthly flows are less than one percent for all seasons.
Table 3.3-14
Comparison of Mean Monthly Flow (cfs) – Baseline Conditions and Surplus Alternatives
Colorado River Upstream of CRIR Diversion (River Mile = 180.8)
th
70 Percentile Values for Year 2016

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
Mean Monthly Flows (cfs) for Year 2016 at the 70 Percentile
mb
ation on Nove
Shortage
jo N
Protection
Baseline
Six States
California
av States Flood Control
NBasina archived
in
3880
3897
4117
4012
cited3897 6864,3895
11690
11690
11690
11690
12009
11793
4-1
1
No. 13025
12990
12989
13025
13194
12984
th

Season
Winter
Spring
Summer
Fall

8005

7934

8064

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-58

8005

7987

7895

0%

25%

3.3-59

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Winter Season Flows
as Represented by January Flows

Figure 3.3-23a
Colorado River Seasonal Flows Upstream of Colorado River Indian Reservation
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-60

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Spring Season Flows
as Represented by April Flows

Figure 3.3-23b
Colorado River Seasonal Flows Upstream of Colorado River Indian Reservation
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-61

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Summer Season Flows
as Represented by July Flows

Figure 3.3-23c
Colorado River Seasonal Flows Upstream of Colorado River Indian Reservation
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-62

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Fall Season Flows
as Represented by October Flows

Figure 3.3-23d
Colorado River Seasonal Flows Upstream of Colorado River Indian Reservation
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

3.3.4.5.3 River Flows Between Palo Verde Diversion Dam and Imperial Dam
The flow of the Colorado River between Palo Verde Diversion Dam and Imperial Dam
is normally set at the amount needed to meet the United States diversion requirements
downstream of the Palo Verde Diversion plus deliveries to Mexico. The river location
that was modeled for this reach of the river is located immediately downstream of the
Palo Verde Diversion Dam.
As discussed in Section 3.3.4.5.2, the proposed California water interstate transfers are
included in the simulation of the baseline conditions and surplus alternatives.
The 90th, 50th, and 10th percentile annual flow volumes for this reach are shown in
Figure 3.3-24. As shown by the 50th percentile values, annual flow volumes in this
reach can be expected to be greater for the California and Shortage Protection
alternatives than for the baseline conditions for the first few years of the 15-year interim
surplus criteria period. This is a result of more frequent surplus deliveries. The largest
increases from baseline conditions occur under the California Alternative and are
approximately eight percent during the years 2002 through 2007. After 2007, the
annual flow volumes are identical to the baseline conditions. Annual flow volumes
under the Shortage Protection Alternative are approximately five percent during the
ior
In er 17
years 2002 through 2011. After 2011, the annual flow volumes aret identical to the
0
f theand Basin
baseline conditions. Results for the Flood Control, pt. States, r 29, 2 States
Six o
e
e
v. D
alternatives are identical to those undertthe baseline ovemb for the entire period
a ion on N conditions
N
(2002 through 2050).
vajo
ed

in Na
rchiv
ited level,864, a
c
At the 10 percentile -16 the California Alternative has the same relative difference
(eight percent)No.the years 2002 and 2003, while the Shortage Protection Alternative
for 14
th

exhibits the same relative difference (five percent) for the years 2002 through 2005. All
other results are identical to those observed for the 50th percentile values.
At the 90th percentile level, all surplus alternatives (except for the Flood Control
Alternative) show annual flow volumes less than or equal to the flows under the
baseline conditions. This is the result of more frequent surplus deliveries, which tend to
lower Lake Mead reservoir levels. With lower reservoir levels, the frequency of flood
control events (which contribute most of the flows at the 90th percentile level) is
decreased, which in turn decreases the annual flow volume for a given percentile. The
California and Shortage Protection alternatives exhibit the largest decreases, ranging
from approximately 17 percent less than baseline conditions in 2006 to four percent less
by 2023. Results for the Six States and Basin States alternatives are similar to each
other, ranging from approximately 11 percent less than baseline conditions in 2016 to
four percent less by 2023.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-63

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

In Figure 3.3-25, the cumulative distribution of annual flow volumes is shown for year
2006. This is the year of the largest differences at the 90th percentile level as shown in
Figure 3.3-24. Although the annual flow volumes decrease for all surplus alternatives
(except Flood Control Alternative) at a fixed percentile (i.e. at the 90th percentile) as
compared to baseline, the range of annual flow volumes are the same for baseline
conditions and the surplus alternatives. The frequency that a flow of a specific
magnitude will occur, however, is lower under the surplus alternatives (except for the
Flood Control Alternative) as shown in Figure 3.3-25.
Figures 3.3-26 (a-d) present comparisons of the representative seasonal flows under
baseline conditions and the surplus alternatives for 2016. As expected, the largest flows
occur in the spring and summer seasons for baseline conditions and all alternatives due
to downstream irrigation demands. For flows that are due primarily to flood control
releases from Lake Mead (flows in the 90th – 100th percentile range), the range of mean
monthly flows is not changed by the different surplus alternatives, since these
magnitudes are dictated by the flood control regulations. These flows occur, however,
less often for the surplus alternatives (except the Flood Control Alternative). This effect
is less pronounced in July, when most flood control releases have ceased.
The differences in flows not due to flood control releases are similar rior alternatives
for all
th Inte
and baseline conditions. A numerical comparison are thef70 e
th percentile 17 is
20 values
pt. o er 29 the
shown in Table 3.3-15. The differences in mean monthly flows for , California
. De
b
Alternative compared to baseline conditions v approximately 10 percent in the winter,
ion are Novem
at
seven percent in the spring,avajo N in ed summer, and eight percent in the fall. For
six percent the on
N the meanhiv
in
the Basin States Alternative, 4, arc monthly flows are identical to those under
cited all686
baseline conditions for -1 seasons.
4

No.

1

Table 3.3-15
Comparison of Mean Monthly Flow (cfs) – Baseline Conditions and Surplus Alternatives
Colorado River Downstream of Palo Verde Diversion Dam (River Mile = 133.8)
th
70 Percentile Values for Year 2016
Mean Monthly Flows (cfs) for Year 2016 at the 70th Percentile
Season
Baseline

Basin States

Flood Control

Six States

California

Shortage
Protection

Winter

3516

3516

3516

3516

3865

3760

Spring

9888

9888

9888

9888

10608

10392

Summer

10729

10729

10729

10729

11426

11217

Fall

7191

7191

7191

7191

7749

7582

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-64

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

Figure 3.3-24
Colorado River Downstream Palo Verde Diversion Dam Annual Flow Volume (af)
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values
90th Percentile
12,000,000

Annual Flow Volume (af)

11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

10,000,000
9,000,000
8,000,000
7,000,000
6,000,000

5,000,000

50th Percentile
12,000,000

ior
Inter 17
10,000,000
0
f the
pt. o er 29, 2
e
9,000,000
v. D
mb
ation on Nove
jo N
8,000,000
Nava archived
in
7,000,000
cited 16864,
146,000,000
No.

Annual Flow Volume (af)

11,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

5,000,000

10th Percentile
12,000,000

Annual Flow Volume (af)

11,000,000
10,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

9,000,000
8,000,000
7,000,000
6,000,000
5,000,000
2000

2005

2010

2015

2020

2025
Year

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-65

2030

2035

2040

2045

2050

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

10,000,000

11,000,000

12,000,000

13,000,000

14,000,000

15,000,000

0%

25%

3.3-66

Percent of Values Less than or Equal to

50%

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
Baseline Conditions

90th Percentile

Figure 3.3-25
Colorado River Annual Flow Volumes Downstream of Palo Verde Irrigation Diversion
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2006

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Flow Volume (af)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-67

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Winter Season Flows
as Represented by January Flows

Figure 3.3-26a
Colorado River Seasonal Flows Downstream of Palo Verde Diversion Division
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-68

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Spring Season Flows
as Represented by April Flows

Figure 3.3-26b
Colorado River Seasonal Flows Downstream of Palo Verde Diversion Division
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-69

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Summer Season Flows
as Represented by July Flows

Figure 3.3-26c
Colorado River Seasonal Flows Downstream of Palo Verde Diversion Division
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-70

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Fall Season Flows
as Represented by October Flows

Figure 3.3-26d
Colorado River Seasonal Flows Downstream of Palo Verde Diversion Division
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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CHAPTER 3

3.3.4.5.4 River Flows Between Imperial Dam and Morelos Dam
The flows in the Colorado River below Imperial Dam are primarily comprised of the
water delivered to Mexico in accordance with the Treaty. Mexico's principal diversion
is at Morelos Dam, which is located, approximately nine miles southwest of Yuma,
Arizona. Mexico owns, operates, and maintains Morelos Dam.
The reach of river between Morelos Dam and the SIB is commonly referred to by
Reclamation as the Limitrophe Division. Reclamation's authority in this division is
limited to maintaining the bankline road, the levee, various drains to the river, and the
U.S. Bypass drain that carries agricultural drainage water to the Cienega de Santa Clara
in Mexico. Under International Treaty the United States Section of the IBWC is
obligated to maintain the river channel within this division. Reclamation provides
assistance to the IBWC, when requested, for maintenance needs in this reach of the
river.
Minute 242 (Minutes are defined as decisions of IBWC and signed by the Mexican and
United States commissioners) of IBWC and the Mexican Water Treaty of 1944 provide
requirements for deliveries at the NIB and SIB near Yuma and San Luis, Arizona,
respectively. Up to 140,000 af annually of agricultural drainage wateror be delivered
eri can
to Mexico at the SIB. The remaining 1,360,000 af of waterthe Int delivered to Mexico
is to be
017
f
at the NIB annually and diverted at Morelos Dam eptheo
to t. Mexicali Valley. For several
29, 2
D
ber
years after the United States Bypass Drainn v. completed in 1978, the Colorado River
io was Novem
at
Channel downstream of Moreloso N was d on
vaj Damhive normally dry. Flows below Morelos Dam
a
now occur only when in N in excess of Mexico's requirement arrive at the NIB.
d water , arc

cite 16864
14Much of the NIB water is diverted at Imperial Dam into the All-American Canal (AAC)
No.
where it is returned to the bed of the Colorado River through Siphon Drop and Pilot
Knob Powerplants. A portion of the NIB deliveries remains in the river, passing
through Imperial and Laguna Dams to Morelos Dam.

Water in excess of Mexico's water order at the NIB is normally passed through Morelos
Dam, through the Limitrophe Division, and into the original Colorado River channel
downstream. Water in excess of Mexico's water order occurs primarily when flood
releases are made from Lake Mead. Excess water arriving at the NIB may also result
from flooding on the Gila River, and from operational activities upstream (i.e.,
cancelled water orders in the United States, maintenance activities, etc.).
In December of each year, Mexico provides to the United States an advance monthly
water order for the following calendar year. Normally, this water order can only be
changed by providing the United States with written notice, 30 days in advance and
each monthly water order can be increased or decreased by no more than 20 percent of
the original monthly water order. The Treaty further stipulates that Mexico's total water
order must be no less than 900 cfs and no more than 5500 cfs during the months of
January, February, October, November and December. During the remainder of the

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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year, Mexico's water order must be no less than 1500 cfs and no more than 5500 cfs.
Daily water orders are usually not allowed to increase or decrease by more than 500 cfs.
As discussed in Section 3.3.3.3, the model accounts for the all deliveries to Mexico
diversions at the NIB (Morelos Dam). Flows that are modeled downstream of Morelos
Dam represent mean monthly flows that are excess flows in the Colorado River due to
Lake Mead flood control releases. These excess flows may reach the Colorado River
Delta, although Mexico has the authority to divert them for other uses. Such decisions
by Mexico are not modeled. The excess flows are over and above Mexico’s normal 1.5
mafy water entitlement, plus the 200,000 afy for surplus deliveries.
The 90th, 50th, and 10th percentile annual flow volumes for this reach are shown in
Figure 3.3-27. Since these flows are dependent solely upon infrequent flood control
releases, no flows are observed at either the 10th or 50th percentiles. At the 90th
percentile level, all surplus alternatives (except for the Flood Control Alternative) show
annual flow volumes less than or equal to the flows under the baseline conditions. This
is the result of more frequent surplus deliveries, which tend to lower Lake Mead
reservoir levels. With lower reservoir levels, the frequency of flood control events is
decreased, which in turn decreases the annual flow volume for a given percentile. The
California and Shortage Protection alternatives exhibit the largest decreases, ranging
ior
Inter 12 7
from approximately 70 percent less than baseline conditionshe 2016 to01 percent less
in
of t
9 2
by 2023. Results for the Six States and Basin Statespt.
alternatives are ,similar to each
D
.lesse ember 2
other, ranging from approximately 47ation v
percent
than
Nov baseline conditions in 2013 to
12 percent less by 2023. avajo N ved on

N
hi
ed in 864 arc
itthe cumulative,distribution of annual flow volumes is shown for year
c
In Figure 3.3-28,
-16
o. 14
2006. This is the year of the largest differences at the 90th percentile level as shown in
N
Figure 3.3-27. Although the annual flow volumes decrease for all surplus alternatives
(except Flood Control Alternative) at a fixed percentile (i.e. at the 90th percentile) as
compared to baseline, the range of annual flow volumes are the same for baseline
conditions and the surplus alternatives. The frequency that a flow of a specific
magnitude will occur, however, is lower under the surplus alternatives (except for the
Flood Control Alternative) as shown in Figure 3.3-28.
Additional analysis of annual flow volumes in this reach is presented in Section 3-16.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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Figure 3.3-27
Colorado River Below Mexico Diversion at Morelos Dam Annual Flow Volume (af)
Comparison of Surplus Alternatives to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values
90th Percentile

5,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

Annual Flow Volume (af)

4,000,000

3,000,000

2,000,000

1,000,000

0

50th Percentile
5,000,000

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.
Annual Flow Volume (af)

4,000,000

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

3,000,000

2,000,000

1,000,000

0

10th Percentile
5,000,000

Annual Flow Volume (af)

4,000,000
Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

3,000,000

2,000,000

1,000,000

0
2000

2005

2010

2015

2020

2025

Year

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-73

2030

2035

2040

2045

2050

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

0%

10%

20%

30%

50%

60%

3.3-74

Percent of Values Less than or Equal to

40%

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

70%

80%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
Baseline Conditions

90th Percentile

Figure 3.3-28
Colorado River Annual Flow Volumes Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2006

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Flow Volume (af)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

90%

100%

CHAPTER 3

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CHAPTER 3

Figures 3.3-29 (a-d) present comparisons of the representative seasonal flows under
baseline conditions and the surplus alternatives for 2016. As expected, the only
differences are seen for flows that are due to flood control releases from Lake Mead
(flows in the 90th – 100th percentile range). As seen in the figures, the range of mean
monthly flows is not changed by the different surplus alternatives, since these
magnitudes are dictated by the flood control regulations. These flows occur, however,
less often for the surplus alternatives (except the Flood Control Alternative). This effect
is less pronounced in July, when most flood control releases have ceased.
A numerical comparison of the 90th percentile values is shown in Table 3.3-16. The
differences in mean monthly flows for the California Alternative compared to baseline
conditions are approximately 51 percent in the winter, zero percent in the spring, zero
percent in the summer, and 100 percent in the fall. For the Basin States alternative, the
differences (compared to baseline conditions) in mean monthly flows are approximately
one percent in the winter, zero percent in the spring, and zero percent in the summer and
100 percent in the fall seasons. The large fluctuating differences are due to the
infrequent nature of these flows and are indicative of the decreased frequency of
occurrence due to the interim surplus criteria.

ior
Inter 17
0
f the
pt. o er 29, 2
e
.D
b
ion v N 2016 atm
atFlows (cfs) for Yearove the 70 Percentile
Mean Monthly
on
jo N
Shortage
Nava archived
in
Protection
States
Baseline
Flood Control
Six States
California
ited 6Basin4,
c
86 8052
8125
8052
3983
2706
4-1
. 18125
No
0
0
0
0
0
0

Table 3.3-16
Comparison of Mean Monthly Flow Data – Baseline Conditions and Surplus Alternatives
Colorado River Downstream of Morelos Dam (River Mile = 23.1)
th
90 Percentile Values (cfs) for Year 2016
th

Season
Winter
Spring
Summer
Fall

0

0

0

0

0

0

3007

0

3007

0

0

0

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.3-75

0%

25%

3.3-76

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Winter Season Flows
as Represented by January Flows

Figure 3.3-29a
Colorado River Seasonal Flows Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-77

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Spring Season Flows
as Represented by April Flows

Figure 3.3-29b
Colorado River Seasonal Flows Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-78

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Summer Season Flows
as Represented by July Flows

Figure 3.3-29c
Colorado River Seasonal Flows Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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0%

25%

3.3-79

Percent of Values Less than or Equal to

50%

75%

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

0

5,000

10,000

Flo
w
(cf 15,000
s)

20,000

25,000

30,000

Fall Season Flows
as Represented by October Flows

Figure 3.3-29d
Colorado River Seasonal Flows Below Mexico Diversion at Morelos Dam
Comparison of Surplus Alternatives to Baseline Conditions for Modeled Year 2016

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

100%

CHAPTER 3

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3.5
3.5.1

CHAPTER 3

WATER QUALITY
INTRODUCTION

This section addresses the salinity of the Colorado River and mainstream reservoirs, and
the quality of Lake Mead water available for municipal and industrial purposes. The
potential changes in the operation of the Colorado River system downstream from Lake
Powell under interim surplus criteria alternatives could temporarily affect the salinity of
Colorado River water, which affects municipal and industrial uses in the Lower Basin.
In addition, changes in Lake Mead water levels could affect the quality of water arriving
at the SNWS pump intakes in the Boulder Basin of Lake Mead, and thereby affect the
quality of the water supply for the Las Vegas Valley.
3.5.2

COLORADO RIVER SALINITY

This section discusses potential effects that could result from the implementation of the
interim surplus criteria alternatives under consideration. Salinity has long been
recognized as one of the major problems of the Colorado River. “Salinity” or “total
dissolved solids” (TDS) include all of the soluble constituents dissolved in a river and
the two terms are used interchangeably in this document. This sectionior
er considers
e Int 017
hto Imperial Dam. The
potential changes in salinity concentrations from Lake.Mead
2
of t
ept effectsr of 9,
section also presents a general discussion of the D
. adverse mbe 2 increased salinity
nv
e
concentrations on municipal and o Natio systems. ov
industrial
nN

vaj
ed o
in Na 4, archiv
3.5.2.1
METHODOLOGY 6
cited 168
. 14Reclamation’sNo
model for salinity is used to create salinity reduction targets for the

Colorado River Basin Salinity Control Program (SCP). To do this, the model simulates
the effects of scheduled water development projects to predict future salinity levels.
This data is then used to compute the amount of new salinity control projects required to
reduce the river’s salinity to meet the standards at some point in the future (2015). The
model itself does not include future salinity controls because implementation schedules
for future salinity control projects are not fixed and vary considerably. The salinity
control standards are purposefully designed to be long-term (nondegradation) goals,
rather than exceedence standards used for industry or drinking water.
By definition, the SCP is designed to be flexible enough to adjust for any changes
caused by the various alternatives being considered. Therefore, it could be concluded
that there would be no change in compliance with the standards caused by selecting any
one of the alternatives. However, for the purposes of this analysis, each alternative has
been evaluated using fixed (existing) levels of salinity controls to identify the
differences between alternatives and the baseline conditions.

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General effects of salinity were determined from review of records of historic river flow
and salinity data available and economic impacts presented in Quality of Water
Colorado River Basin – Progress Report No. 19, 1999, U.S. Department of the Interior;
Water Quality Standards for Salinity Colorado River System, 1999 Review, June 1999,
Colorado River Basin Salinity Control Forum and Salinity Management Study,
Technical Appendices, June 1999, Bookman-Edmonston Engineering, Inc.
The salinity program as set forth in the Forum's 1999 Annual Review enables the
numeric criteria to be met through the year 2015. Therefore, it was presumed that the
criteria would be maintained through 2015. Although the 1999 Review considers only
the period to 2015, it was presumed that future additions to the salinity control program
will be sufficient to maintain the criteria through 2050.
3.5.2.2
3.5.2.2.1

AFFECTED ENVIRONMENT
Historical Data

The Colorado River increases in salinity from its headwaters to its mouth, carrying an
average salt load of nine million tons annually past Hoover Dam. Approximately half
(47 percent) of the salinity concentration is naturally caused and 53erior of the
t percent
he Inrunoff,17
concentration results from human activities including agricultural
20 evaporation
of t
ep . ber 29,
and municipal and industrial sources (Forum, 1999). t
v. D

n
em
Natio d on Nov period of record 1941 through
Salinity of the river has fluctuated significantly over the
vajo
e
in Na 4, archiv concentrations have ranged from 833
1997. Below Hoover Dam, annual salinity
d
cite
86
milligrams per liter 14-16in 1956 to 517 mg/l in 1986. However, the maximum
. (mg/l)
No
monthly fluctuation in any year is approximately 50 mg/l. Salinity of the river is
influenced by numerous factors including reservoir storage, water resource development
(and associated return flows), salinity control, climatic conditions and natural runoff.
The impact of reservoir storage has all but eliminated seasonal fluctuations in salinity.
Annual variations in salinity are primarily driven by natural, climatic variations in
precipitation and snowmelt runoff. These hydrologic variations cause differences in
both flow and salinity.
As shown in Figure 3.5-1, the salinity of the river varied by as much as 1000 mg/l prior
to the construction of Glen Canyon Dam in 1961. By the 1980s, that variation was
reduced to about 200 mg/l due to the mixing and dampening effect of the large volume
of storage in Lake Powell. Figures 3.5-2 and 3.5-3 show the comparison between
mainstream flows and salinity. Figure 3.5-2 shows the outflow from Glen Canyon and
Imperial Dams. Figure 3.5-3 shows the salinity at Imperial, Hoover and Glen Canyon
dams.

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Figure 3.5-1
Historical Monthly Salinity Concentrations Below Glen Canyon Dam (1940-1995)

1600

1400

Dam closure and reservoir storage in mid1960's reduced variation in salinity

Monthly Salinity (mg/L)

1200

1000

800

600

400

200

0
1940

ior
Inter 17
0
f the
pt. o er 29, 2
e
.D
b
1945
1950
1955
1960
on v 1970 1975 m
ati1965 on Nove 1980 1985 1990
jo N
Nava archived
in
cited 16864,
14No.
Regulatory Requirements and Salinity Control Programs

1995

2000

Year

3.5.2.2.2

In 1972, the EPA promulgated regulations requiring water quality standards for salinity,
numeric criteria and a plan of implementation for salinity control. The Seven Colorado
River Basin States, acting through the Forum, adopted numeric criteria for flowweighted average annual salinity, at three points on the river as shown below:
Below Hoover Dam 723 mg/l
Below Parker Dam

747 mg/l

At Imperial Dam

879 mg/l

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

3.5-3

1970

0

5

10

15

20

25

1975

Imperial Dam

1980

3.5-4

Year

1985

1990

1995

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
Glen Canyon Dam
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Lake Powell fills
in 1980 and the
entire reservoir
system spills in
1983 - 1986.

Figure 3.5-2
Historical Glen Canyon Dam and Imperial Dam Releases

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Annual Discharge (mafy)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2000

CHAPTER 3

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Figure 3.5-3
Historical Salinity Concentrations of Releases
from Glen Canyon, Hoover, and Imperial Dams
1000

900

Imperial Dam

800

Hoover Dam

Salinity (mg/L)

700

600

500

Glen Canyon Dam
400

300

ior
Inter 17
e
0
200
of th
pt.1990 er 29, 2
1970
1975
1980
1985
1995
2000
e
D
Year
mb
n v.
atio
Nove
ajo N ived on
Nav
d in 64, arch
cite 16to
These criteria applied only 8 the lower portion of the Colorado River from Hoover
4Dam to Imperialo. 1 Below Imperial Dam, salinity control is a federal responsibility
N Dam.
to meet the terms of Minute 242 to the U.S.-Mexico Water Treaty of 1944. Minute 242
requires that salinity concentrations upstream of Mexico’s diversion be no more than
115 mg/l + 30 mg/l TDS higher than the average salinity of water arriving at Imperial
Dam.
In 1974, the Colorado River Basin Salinity Control Act (P.L. 93-320) was enacted. The
Act contains two Titles: 1) Title I provides the means for the United States to meet its
commitment to Mexico; and 2) Title II creates a salinity control program within the
Colorado River Basin in order that the numeric criteria will be maintained while the
Basin States continue to develop their apportionment of Colorado River water.
The federal/state salinity control program is designed to maintain the flow-weighted
average annual salinity at or below the numeric criteria. The program is not intended to
counteract short-term salinity variations resulting from short-term water supply. Federal
regulations provide for temporary increases above the criteria due to natural variations
in flows.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

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The seven Basin States acting through the Forum reviews the numeric criteria and plan
of implementation every three years and makes changes in the plan of implementation to
accommodate changes occurring in the Basin States. The latest review was in 1999.
The review is currently undergoing adoption by the Basin States and approval by EPA.
At each triennial review, the current and future water uses are analyzed for their impact
on the salinity of the Colorado River. If needed, additional salinity control projects are
added to the plan to assure compliance with the standards.
The need for one or more additional salinity control projects is determined by
monitoring the salinity of the river and making near-term projections of changes in
diversions from and return flows to the river system. When an additional project is
needed, it is selected from a list of potential projects that have undergone feasibility
investigation. A proposal to implement the project is made through coordination with
the Basin States. In selecting a project, considerable weight is given to the relative costeffectiveness of the project. Cost-effectiveness is a measure of the cost per ton of salt
removed from the river system or prevented from entering the river system. Other
factors are also considered, including environmental feasibility and institutional
acceptability.

ior
Inter 17
It is estimated that 1,478,000 tons of salt will need to beof the or, prevented from
removed
20
ept. ber 29
entering the Colorado River system to maintain D salinity concentration at or below
n v. the o have been controlled and an
em
the criteria through 2015. To date, Nati720,000 tons v
over o
nN
o
vajo
additional 756,000 tons will need to chived
in Na 4, ar be controlled through 2015.
cited 1686
3.5.1.1.3
General Municipal, Industrial, and Agricultural Effects of Increased
14No.
Salinity Concentrations
High salinity concentrations can cause corrosion of plumbing, reduce the life of waterusing appliances, and require greater use of cleaning products. Industrial users incur
extra water treatment costs. Increased salinity in drinking water can create unpleasant
taste, often resulting in the purchase of bottled water or water treatment devices.
Agriculture experiences economic losses from high salinity through reduced crop
productivity and the need to change from less salt-tolerant high value crops, to more
salt-tolerant low value crops. Increased salinity can also require more extensive
agricultural drainage systems.
High salinity is a significant constraint to water recycling and groundwater
replenishment programs. Compliance with regulatory requirements imposed by local
water quality management programs to protect groundwater supplies can add
significantly to the economic impacts. Restrictions have been placed on reuse or
recharge of waters that exceed specific salinity levels. Such restrictions significantly
constrain groundwater replenishment programs and wastewater reuse programs. Should
salinity of the Colorado River increase, these regulatory actions could create a need for

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more expensive water treatment processes, such as reverse osmosis, prior to disposal or
reuse. If disposal is selected, additional water supplies would need to be developed to
meet demands that could have been met by water reuse.
Reclamation has determined that the economic damages from Colorado River salinity in
the three Lower Division states served by Colorado River water amount to $2.5 million
per mg/l. Figure 3.5-4 shows the relationship between costs of damages and salinity
concentrations.
Therefore it is assumed for this analysis that the baseline conditions will reflect the
numeric criteria at each station of interest (below Hoover Dam, below Parker Dam, and
at Imperial Dam).

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

3.5-7

$0.0
400

$0.5

$1.0

$1.5

$2.0

500

600

800

3.5-8

Salinity at Imperial Dam (mg/l)

700

900

1,000

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
At 1997 observed levels
d in 64, arc
cite 168
o. 14
N
At numeric criteria level

Figure 3.5-4
Estimated Cost of Damages Associated with Increased Salinity Concentrations

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Salinity Damages (billions)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

1,100

CHAPTER 3

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3.5.1.3

CHAPTER 3

ENVIRONMENTAL CONSEQUENCES

The effects of the alternatives on the salinity of Colorado River water focus on their
differences from baseline conditions. Since the current model configuration does not
include any salinity control projects beyond those currently in place, modeling of
baseline conditions indicates increases in salinity due to projected increased water
consumption in the Upper Basin. However, in practice, these increases would be offset
by salinity control projects that would continue to be implemented.
Tables 3.5-1 and 3.5-2 present these differences for years 2016 and 2050, respectively.
The TDS values represent the mean values for the flow-weighted annual averages for
the given year. The first column under each monitoring station heading in the tables
presents the model projected TDS concentrations under the five alternatives calculated
by applying the difference to the baseline TDS level. The second column presents the
difference between the values for each alternative compared with baseline conditions.
As shown in Table 3.5-1, there is, in general, very little effect on TDS (less than one
percent) due to interim surplus criteria in the year 2016. The exception is the decrease
at Imperial Dam for the California Alternative of 19 mg/l (about 2.2 percent). This is
r
due to the assumption in the model of an additional transfer fromnterioto MWD of
I PVID 17
100,000 af during normal and Tier 3 surplus conditions,of the reduces 0 salt pickup
which
2 the
ept. ber 29,
in the return flows.
v. D
m

n
e
Natio d on Nov
ajo tend itoe
In general, the surplus alternatives h v decrease TDS values slightly. These
Nav
d in 64, arc
decreases are duete increased equalization releases from Lake Powell relative to
ci to 168
baseline.
14No.

As shown in Table 3.5-2, interim surplus criteria have no effect on TDS values by the
year 2050, with the exception of the PVID to MWD transfer assumed in the California
Alternative.
3.5.3

LAKE MEAD WATER QUALITY AND LAS VEGAS WATER SUPPLY

This analysis addresses potential impacts of interim surplus criteria alternatives on water
quality in Lake Mead, and potential changes to water quality and levels of contaminants
at the SNWA intakes. This is a qualitative analysis based on system modeling and
existing limnological studies.
3.5.3.1

METHODOLOGY

Evaluation of the environmental consequences of each operational alternative to Lake
Mead water quality and Las Vegas water supply are based on a qualitative assessment of
existing limnological and hydrodynamic data, and hydrologic modeling as discussed in
Section 3.3. Each interim surplus criteria alternative was modeled for comparison to
baseline projections. Modeling focused on the probability of decreased Lake Mead

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Table 3.5-1
Estimated Colorado River Salinity in 2016
Unit: Total Dissolved Solids (mg/l)

Below Hoover Dam
Alternative
Value

Below Parker Dam

At Imperial Dam

Departure
from
Baseline

Value

Departure
from
Baseline

Value

Departure
from
Baseline

Baseline
1
Conditions

723

NA

747

NA

879

NA

Basin States

719

-2

737

-2

879

0

Flood Control

723

0

745

-0

879

0

Six States

719

-2

738

-2

881

0

California

712

-5

734

-5

853

-19

Shortage
Protection

715

-4

736

-4

872

-3

1

ior
Inter 17
0
f the
pt. o er 29, 2
e
.D
mb
ion v
atTable 3.5-2 Nove
on
jo N ve River
Estimated
i
Nava aColoradod Salinity in 2050
in
rch
64,
cited 168Unit: Total Dissolved Solids (mg/l)
14Below Parker Dam
At Imperial Dam
No. Below Hoover Dam

Baseline conditions assume compliance with the numeric criteria at the locations cited.

Value

Departure
from
Baseline

Value

Departure
from
Baseline

Value

Departure
from
Baseline

Baseline
1
Conditions

723

NA

747

NA

879

NA

Basin States

723

0

747

0

877

0

Flood Control

723

0

747

0

879

0

Six States

723

0

747

0

878

0

California

722

-1

745

0

857

-24

Shortage
Protection

722

-1

747

0

876

0

Alternative

1

Baseline conditions assume compliance with the numeric criteria at the locations cited.

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surface elevations, which could exacerbate effects of discharge of Las Vegas Wash
water into Boulder Basin.
Assessment of potential effects on water quality of Lake Mead, including consideration
of Las Vegas Wash inflow on the SNWA intake, relied primarily on system modeling
information associated with the probability of future Lake Mead surface elevations.
Previous studies of Lake Mead were also an important source of information,
particularly those focusing on Boulder Basin, Las Vegas Wash, and hydrodynamics
potentially affecting intake water quality.
As discussed in Section 3.3, modeling identified probabilities associated with surface
water elevations under baseline conditions as well as projections associated with
implementation of the interim surplus criteria alternatives over a 50-year period. As
discussed previously, model output utilized for this water quality analysis assumes
shortage determinations would occur, if necessary, to protect a surface elevation of 1083
feet msl, which is the Lake Mead minimum power pool elevation. The primary SNWA
intake at Saddle Island is at 1050 feet msl, and the secondary intake is at 1000 feet msl.
Thus, assuming a strategy to protect 1083 feet msl also provides a level of protection to
SNWA’s intake water quality.

ior
Inter 17
As discussed below, contaminant dilution and lake water f the are, directly
o quality29 20
ept. in berassessment is a
proportional to lake volume. As such, a critical D
v. element mthis
ation on Nthee
comparison of projected Lake Mead volumes under ov five action alternatives relative
jo N ved
to baseline conditions. n Navhydrologic modeling output, median Lake Mead volumes
Using a
i
rchi
and surface areastwere identified for each of the alternatives associated with projected
i ed 6864, a
c
reservoir elevations14-1 the median modeled probabilities. Modeling results
under
No.
indicating these parameters were then developed for the years 2016, 2026, 2036, and
2050. Separate comparisons were then made of the volume and surface area for each
alternative as compared to baseline conditions.
3.5.3.2

AFFECTED ENVIRONMENT

The focus of this section is a description of the affected environment related to Lake
Mead water quality and the SNWA intake locations, with specific consideration of
hydrodynamics of the Colorado River Basin, limnology and water quality (factors that
may be influenced by implementation of interim surplus criteria alternatives).
3.5.3.2.1

General Description

Lake Mead is a large mainstream Colorado River reservoir in the Mohave Desert, within
the States of Arizona and Nevada as shown on Map 3.2-1. Lake Mead, formed in 1935
following the construction of Hoover Dam, is the largest reservoir in the United States
by volume (26 maf active storage). At full pool (reservoir elevation 1221 feet msl),
Lake Mead extends 108 miles from Black Canyon (Hoover Dam) to Separation Canyon

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at the upstream end. Lake Mead has four large sub-basins including Boulder, Virgin,
Temple and Gregg. Between these basins are four narrow canyons: Black, Boulder,
Virgin and Iceberg. Over 170,000 square miles of the Colorado River Basin watershed
are located above Hoover Dam. Boulder Basin, SNWA intake locations and the Las
Vegas Wash are shown on Map 3.5-1.
The Muddy and South Virgin mountains border the reservoir on the north, and the
Virgin and Black mountains and various desert hills border the reservoir on the south.
The shoreline is extremely irregular with a Shoreline Development Value (SLD) of 9.7
(Paulson and Baker, 1981). SLD is the ratio of the length of the shoreline of a lake or
reservoir to the length of the circumference of a circle with an area equal to that of the
lake (Wetzel, 1975). The shoreline includes several large bays, including Las Vegas
and Bonelli, and numerous coves. The principal morphometric characteristics of Lake
Mead are summarized below in Table 3.5-3.
Table 3.5-3
Morphometric Characteristics of Lake Mead
Parameter

Units

Value

ior 1,205
Inter 17 590
0 180
f the
pt. o er 29, 2
e
v. D
231
mb
ation on Nove
N
30
jo
108
Nava archived
in
17
cited 16864,
9.7
. 14No

Normal operating level (spillway crest)
Maximum depth
Mean depth
Surface area
Volume (including dead storage)
Maximum length
Maximum width
Shoreline development
Discharge depth
Annual discharge (approximate)
Replacement time at maximum operating level

feet
feet
feet
square miles
maf
miles
miles
Index Value
feet
maf
years

310
10
3.9

Derived from Interior (1966), Lara and Sanders (1970), Hoffman and Jonez (1973)

LaBounty and Horn (1997) conducted a study of the influence of drainage from the Las
Vegas Valley on the limnology of Boulder Basin that is highly relevant to the issue
addressed in this section. Unless otherwise noted, the descriptions of reservoir
characteristics, hydrodynamics, and general limnology of Lake Mead are drawn from
this study.
The Colorado River contributes about 98 percent of the annual inflow to Lake Mead;
the Virgin and Muddy rivers and Las Vegas Wash provide the remainder. Annual flows
from Las Vegas Wash are approximately 155,000 af, providing the second highest
inflow into Lake Mead. Discharge from Hoover Dam is hypolimnetic and occurs 285
feet below the normal operating shown above (1205 feet msl). Average annual
discharge is approximately 10 maf.

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Boulder Basin, the lowermost basin of Lake Mead, receives all nonpoint surface and
groundwater discharges and treated effluent from the Las Vegas Valley and municipal
wastewater treatment facilities via drainage from Las Vegas Wash into Las Vegas Bay.
Boulder Basin is 9.3 miles wide from Boulder Canyon to Hoover Dam (Black Canyon),
and the distance from the confluence of Las Vegas Wash to Hoover Dam is
approximately 9.9 miles. The historical Colorado River channel lies along the eastern
side of Boulder Basin.
Due to effects of urban runoff and treatment plant effluents on the discharge through
Las Vegas Wash (discussed later in this section), Boulder Basin has the highest nutrient
concentrations in the Lake Mead system (Paulson and Baker, 1981; Prentki and Paulson,
1983). This is in contrast to the normal upstream-downstream decrease in the pattern of
productivity more typical of reservoirs, and results in several limnological features
within Boulder Basin that are normally associated with upstream reaches (Kimmel et al.,
1990).
Overall, Lake Mead is mildly mesotrophic based on several classification indices
(Vollenweider 1970; Carlson 1977), including chlorophyll a concentration and secchi
transparency measurements. Chlorophyll concentration is a measure of algal biomass
ior
and can, therefore, be interpreted as an index of lake productivity. tSecchi disk
In er 17
e
measurements are used to determine the depth to which of thpenetrates0
pt. light er 29, 2 lake water and
help to establish the euphotic zone which marksDe areamb lake where primary
v. that ve of a
o
ation on Noccurs.
productivity (energy production jby N
o photosynthesis)

va
ed
in Na 4, archiv
d input into Las Vegas Bay, chlorophyll concentrations have
Due to abundantinutrient 686
c te 1
3
been measured greater o. 14than 100 milligrams per cubic meter (mg/m ). Secchi
N
transparency readings of less than two feet have been measured in the inner bay

(LaBounty and Horn, 1997). However, secchi transparency increases to over 16 feet,
and chlorophyll a is reduced by 90 percent within the first 2.6 miles from the Las Vegas
Wash inflow. These findings suggest that Boulder Basin is a relatively isolated
embayment and that it is much more productive than the lake as a whole.

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3.5-14

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Map 3.5-1
Las Vegas Wash and SNWA Lake Mead Intake Facilities at Saddle Island

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

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The Federal Water Pollution Control Act (Clean Water Act) Amendments of 1972 and
1977 require the control of all sources of water pollution in meeting the goals of the Act.
Section 208 of the Act requires that all activities associated with water pollution
problems are planned and managed through an integrated area-wide water quality
management program. It also defines the schedule and scope of area-wide wastewater
treatment management plans. The 1997 Las Vegas Valley 208 Water Quality
Management Plan Amendment certified by the State of Nevada and EPA, is a 20-year
plan that comprehensively addresses the quality and quantity of the Valley’s point
source (discharges from wastewater treatment facilities) and non-point sources
(groundwater, stormwater issues, Las Vegas Wash, agricultural diffuse sources), and
revisions of water quality standards.
The water quality requirements currently being met by the wastewater discharges of the
Las Vegas Valley have a long history. Beginning in the 1950s with requirements for
secondary treatment, through the 1970s and the promulgation of the Clean Water Act,
and into the 1990s with more advanced nutrient removal requirement, the quality and
volume of treated wastewater discharged to Lake Mead has continued to increase and
will continue to meet standards into the future through the Section 208 process (Clark
County, 1997).
r

terio
he In 2017
The Lake Mead Water Quality Forum, established bytthe f t
p . o Nevada Division of
29,
Environmental Protection (NDEP), has been v. De ember as an avenue for
identified in the Plan
n
coordinated research opportunities and tsolutions to the water quality issues that face Las
Na io d on Nov
ajo
e
Vegas Valley and Laken Navin therfuture. The forum is comprised of federal, state and
i Mead 4, a chiv
d vested interest in Lake Mead’s water quality. The Lake Mead
cite 1686
local agencies with a
Water QualityNo. 14 responsible for issue identification, coordination and defining
forum is
the process approach in identifying issues regarding water quality and potential impacts
to the water supply. The Las Vegas Wash Coordination Committee (LVWCC) is
comprised of more than two dozen members of local, state, and federal agencies,
business owners and members of the public. The LVWCC was tasked with the support,
development and implementation of the Las Vegas Wash Comprehensive Adaptive
Management Plan (LVWCAMP). The planning phase of the LVCAMP is now
complete, and various actions presented in the plan are currently in progress to restore
the wash, its wetlands, and its ability to improve the quality of return flows into Lake
Mead. Reclamation is an active member of both of these groups and has been
independently funding research on Lake Mead water quality prior to their formation and
is now a funding partner with other agencies for ongoing studies on the Wash and Lake
Mead. Water quality in Lake Mead and Las Vegas Wash are the subject of numerous
articles and the chemical and physical analyses of raw and treated Lake Mead source
water is published on SNWA’s website (http://www.snwa.com).

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3.5.3.2.2

CHAPTER 3

Lake Mead Water Quality and Limnology

Water quality of Lake Mead and the Colorado River is alkaline with a pH of 8.3 and an
average concentration of TDS of approximately 700 mg/l. Chemical characteristics of
the river at the inflow to Lake Mead, near the outflow at Hoover Dam, and at Lake
Mohave are shown below in Table 3.5-4.
Table 3.5-4
Chemical Characteristics of Colorado River

Parameter
pH
Conductivity
Total Dissolved Solids
Calcium
Magnesium
Potassium
Bicarbonate
Sulfate
Chloride
Silica
Nitrate
Phosphate
1

Gage Station Location1

Units

umho/cm
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l

Grand Canyon
2

Hoover Dam

Davis Dam

8.0
945
617
74
26
4.1
170
228
79
7.0
.50
.010

7.7
1086
705
86
28
4.9
163
283
85
8.3
.41
.013

8.0
1089
714
84
29
5.0
157
293
87
7.8
.28
--

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
i
NavaSeptemberved
USGA data, average ford in 1975 – arch 1976
ite October6864,
c
-1
o. 14
N

The principal constituents of TDS are the anions of sulfate, carbonate and chloride and
the cations of sodium, calcium, magnesium and potassium. Nitrate concentrations are
moderate (0.28 to 0.50 mg/l), but phosphorus is extremely low (0.01 to 0.03 mg/l).
Silica is present in very high concentrations (7.0 to 8.3 mg/l).
Limnological investigations of Lake Mead have found that 80 percent of the inorganic
nitrogen within the lake is provided by the Colorado River, and that Las Vegas Wash
contributes 70 percent of the inorganic phosphorus (Paulson, Baker, Deacon, 1980).
The Upper Basin of Lake Mead was found to be phosphorus-limited, and the Lower
Basin nitrogen-limited during the summer. Equal proportions of nitrogen and
phosphorous were retained in the Upper Basin of Lake Mead, but nitrogen retention
decreased to seven percent, and phosphorus to 33 percent in the Lower Basin.
Additionally, the high nitrate loss from Hoover Dam greatly reduced nitrogen retention
in the Lower Basin of Lake Mead.
In 1978 the EPA estimated that Lake Mead retained 93 percent of the total phosphorus
input versus 52 percent of total nitrogen (EPA, 1978). Phosphorus concentrations are

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low in the Upper Basin of the lake due to the low input from the Colorado River, a
result of sediment trapping that occurs upstream within Lake Powell.
As recently as 1998, new contaminants to Lake Mead have been discovered as a part of
the nonpoint pollutant load of Las Vegas Wash (EPA, 2000). Perchlorate has been
detected in the water of the Colorado River and Lake Mead. Ammonium perchlorate is
manufactured as an oxygen-adding compound in solid rocket fuel propellant, missiles
and fireworks. The EPA identified two facilities that manufactured ammonium
perchlorate in Henderson, Nevada, that were found to have released perchlorate to
groundwater, resulting in four to 16 parts per billion (ppb) concentrations in Lake Mead
and the Colorado River (EPA, 2000).
The NDEP and the SNWA have initiated a collective investigation to locate and clean
up perchlorate in the Colorado River system in coordination with the EPA. The primary
objectives are to locate the source, the groundwater discharge sources, clean it up, and
prevent it from becoming a problem in the future. The EPA has not established
concentration levels of perchlorate because it is not considered a water contaminant.
However, California’s Department of Health Services and NDEP have established an
interim action level of 18 ppb for drinking water. Concentrations lower than 18 ppb are
r
not considered to pose a health concern for the public, includingInterio and pregnant
children
e
17
women. All SNWA drinking water has tested at 11 ppbof th
9, 20
pt. or lower2for perchlorate.
Average perchlorate values for water samples . De emberintake were 9.5 ppb
v collected at their
tion n is not
aPerchlorateNov regulated under the Federal
between June 1999 and August 2000.
ajo N ived o
Safe Drinking Water Act Nav
and thus information is limited regarding its potential health
in
arch
cited 168 how
risks but it is known to affect64, the thyroid processes iodine and is used to treat
Graves Disease. o. 14
N In March 1998, perchlorate was added to the Contaminant Candidate
List as part of the Safe Drinking Water Act due to the concern over potential public
health impact, need for additional research in areas of health effects, treatment
technologies, analytical methods, and more complete occurrence data.
The SNWA identified a major surface flow of perchlorate-laden water from a
groundwater discharge point along Las Vegas Wash in late 1999. Other discharge
points are being investigated. Kerr-McGee Chemical Company, with the NDEP, and
Reclamation as the land management agency, worked together to begin intercepting that
surface flow for treatment. This program is now underway and has significantly
reduced the amount of perchlorate entering the Las Vegas Wash, Lake Mead, and the
Colorado River. This remediation program will continue into the future and will
continue to reduce perchlorate contamination in groundwater and Colorado River water
in Lake Mead and downstream.
In a soon to be published article on contaminants found in Lake Mead fish by Dr. Jim
Cizdziel, University Nevada Las Vegas, only one fish sampled of approximately 300
fish tissues sampled for mercury indicated results above the Federal Department of
Agriculture’s 1.0 ppm level of concern. During this 1998-1999 investigation for metals

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found in Lake Mead fish tissue, most fish sampled for mercury were less than 0.5 ppm
(Pollard, 1999). After reviewing this work, the State of Nevada has decided not to issue
any fish consumption advisories for any contaminates for Lake Mead fish (Pohlmann,
1999).
The rate and volume of inflow from the Colorado River are major determinants of the
limnology of Lake Mead, with minor contributions to volume coming from the Virgin
and Muddy rivers and the Las Vegas Wash (see Table 3.5-5). Due to its lower
conductivity within Lake Mead, Colorado River flows can be identified through the
reservoir. Flows into Lake Mead average approximately 17,900 to 21,400 cfs. During a
seven-day controlled flood in 1996, inflows of 44,600 cfs resulted in a three-foot rise in
surface elevation. Flows of this magnitude influence reservoir limnology of Lake Mead
well into Boulder Basin (LaBounty and Horn, 1997).
Table 3.5-5
Hydraulic Inputs for Lake Mead
Input
Colorado River
Virgin River
Las Vegas Valley Wash
Muddy River

Flow (af)
8,800,000
92,000
59,000
29,000

% of Total
98
1
0.60
0.34

ior
Inter 17
0
f the
pt. o er 29, 2
e
TOTAL INPUT
9,000,000
v. D
mb 100
ation on Nove
jo N
Derived from USGS data from October 1975 – September 1976
Nava archived
in
cited 16864,
14No.
The two major outflows from Lake Mead are both in Boulder Basin: Hoover Dam and
the SNWA intake. Hoover Dam is operated for flood control, river regulation and
power production purposes. The operating elevation for Hoover Dam powerplant
ranges from 1083 feet to a maximum elevation of 1221 feet msl. The dam’s four intake
towers draw water from the reservoir at approximate elevations 1050 and/or 900 feet
msl to drive the generators within the dam’s powerplant. SNWA pumps water from two
adjacent intakes located at Saddle Island that operate down to elevations of 1050 feet
and 1000 feet msl. Hoover Dam outflows vary on a daily basis from approximately
2000 cfs to 50,700 cfs. Capacity of the SNWA intake is 600 cfs. Despite its much
smaller volume, the SNWA intake has been shown to influence deep water currents near
the entrance to Las Vegas Bay (Sartoris and Hoffman, 1971).
LaBounty and Horn (1997) cite the rarity of complete turnover in Lake Mead due to the
great depth (590 feet), and relatively constant temperature gradient. The thermal regime
over the period of 1990 through 1996 was characterized by surface temperatures of 14
degrees Celsius (°C) in December and January to over 30°C in August. Seasonal
thermoclines range from 50 feet in early summer to 100 feet in late summer.
Hypolimnetic temperatures remain near 12°C year-round. Though full reservoir

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turnover seldom occurs, turnover occurs to a depth of approximately 200 to 230 feet in
January and February, a sufficient depth for complete mixing in Las Vegas Bay.
As with other reservoirs, dam operation exerts a great influence on the water quality and
ecology of the system (Thornton, 1990). The hydrodynamics of this large reservoir are
complex and not completely understood. Each basin within Lake Mead is ecologically
unique, and therefore responds differently to the inflow-outflow regime. Furthermore,
the different sources of water entering Lake Mead often retain their identity for
substantial distances into the reservoir and do not necessarily mix completely with the
rest of the water column (Ford, 1990). This spatial heterogeneity can lead to significant
underestimates of actual water retention time, conveyance and fate of materials
transported into the reservoir.
3.5.3.2.3

Hydrodynamics of Lake Mead and Boulder Basin

The Colorado River, Virgin and Muddy rivers and Las Vegas Wash all form density
currents in Lake Mead (Anderson and Pritchard, 1951; Deacon and Tew, 1973; Deacon
1975, 1976, 1977; Baker et al., 1977; Baker and Paulson, 1978). Anderson and
Pritchard (1951) conducted a detailed investigation of density currents in 1948-1949
using temperature and TDS relationships to trace the river inflows.terior found that the
In They
Colorado River flowed along the bottom of the old riverof the in winter 7
channel , 201 (Januaryt.
9
March). The underflow was detectable well v. DepVirginber 2 and at times extended
into the
m Basin
nstrong convergence at the point where river
e
to Boulder Basin. The underflow created a
Natio d o Nov
ajoUp-lakeeflown surface water occurred due to
v
water flowed beneath lake water. chiv
of
in Na
dparallel 64, ar lake water (entrainment) along the boundary of the
frictionally induced,
flow of
ite
c
68
14 1
cold river inflow. .This-produced a large circulation cell in the Upper Basin of Lake
No
Mead, as surface water was pulled up-lake to replace that entrained by the underflow.
Hydrodynamics within Las Vegas Bay have also been the subject of research and are
particularly important from the standpoint of potential interactions between Las Vegas
Wash water and intake water quality. LaBounty and Horn (1997) provide an excellent
discussion of flow patterns in this area of Lake Mead. These authors cite unique
signatures of both Colorado River water and Las Vegas Wash water that allow mapping
of higher conductivity intrusions from Las Vegas Wash into Boulder Basin. Depending
on conditions, the intrusion can be measured for over five miles into Lake Mead.
Seasonally, the Las Vegas Wash intrusion is deepest in January and February (130 to
200 feet) and shallowest in early spring (33 to 50 feet).
Water quality in Las Vegas Wash, and ultimately in Boulder Basin, is heavily
influenced by urban runoff, as well as the treated effluent from three major sewage
treatment facilities upstream. Historically, flows in this basin drained wetlands, which
allowed for natural cooling and nutrient removal. Flows today are warmer and have
doubled in volume over the last 15 years, from 110 cfs to 215 cfs (LaBounty and Horn,

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1997). These factors have tended to force the intrusion higher in the water column of
Las Vegas Bay.
The existence of contaminants in sediments and fish tissue in Las Vegas Bay, and poor
water quality has been well documented (LaBounty and Horn, 1996; Roefer et al., 1996;
Bevans et al., 1996). LaBounty and Horn (1997) cite the relatively close proximity of
the SNWA intake at Saddle Island to potential intrusions of the Las Vegas Wash, and
conclude that changes in hydrodynamics of the basin (i.e., due to drought or
management actions) are critical considerations in assessing effects of the Las Vegas
Wash on drinking water quality.
3.5.3.3
3.5.3.3.1

ENVIRONMENTAL CONSEQUENCES
General Effects of Reduced Lake Levels

This section presents potential water quality changes in Lake Mead associated with
reductions in lake levels, and potential effects of these changes on the concentration of
Las Vegas Wash water at SNWA water supply intakes. In addition, this section
addresses general limnological changes in Lake Mead that may occur under each
r
alternative.
terio

In
7
f he
. ointLake29, 201
pt
It is important to note that estimates of potentialDe
changes
ber Mead surface
v.
elevations are based on system modelingon
Section
i discussed in vem 3.3. Water quality
No
Nat
modeling has not been conducted as a part of this investigation; however, literature
vajo hived on
in Na
review and assumptions with64, arc Las Vegas Wash mixing in the Boulder Basin
ited 68 regard to
c
under various Lake 14-1 elevations have been used to estimate potential future water
Mead
No.
quality conditions.

Results of model runs conducted for this analysis indicate that projections of baseline
conditions and each of the interim surplus criteria alternatives indicate increased
potential over time for the occurrence of declining Lake Mead surface elevations within
and beyond the interim 15-year period, as indicated by the plots of median elevations on
Figure 3.5-5.
The potential degradation of SNWA intake water is not demonstrated quantitatively in
this FEIS, rather the expectation of degradation is based on the assumption that
decreasing lake levels, and therefore lake volume and surface area, could result in
decreased water quality and, more specifically, increased concentration of Las Vegas
Wash inflow at the intake locations. The potential effects associated with Lake Mead
elevation declines are described below, and are followed by a tabular comparison of the
projected Lake Mead volume and surface area changes under the alternatives and
baseline conditions.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

3.5-20

1000
2000

1020

1040

1060

1080

1100

1120

1140

1160

1180

1200

1220

2005

2010

2015

2020

3.5-21

Year

2025

2030

2035

Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative

2040

2045

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
Baseline Conditions
o. 14
N
Basin States Alternative

Figure 3.5-5
Lake Mead End-of-Year Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
th
50 Percentile Values

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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3.5.3.3.1.1

CHAPTER 3

Volume Reduction

Reduction in the volume of Lake Mead would likely have effects on lake water quality
and, potentially, on water quality withdrawn by SNWA. These effects occur as a result
of changes in mixing patterns in Boulder Basin. Given the hydrodynamics of Boulder
Basin associated with the relatively confined nature of the embayment, effects of
reduction in volume of Lake Mead would likely be disproportionately greater in Boulder
Basin than in the lake as a whole. LaBounty and Horn (1997) cite the importance of
salinity and thermal gradients in determining the extent of intrusion of the Las Vegas
Wash into Boulder Basin. Lower lake volumes could increase the overall salinity of the
Boulder Basin, thereby lowering the differential between lake water and inflows of the
Las Vegas Wash. This in turn may act to disperse the intrusion, causing a more diffuse
flow from Las Vegas Wash, a greater concentration of nutrients and contaminants
throughout Boulder Basin, and greater availability of nonpoint contaminants in the
vicinity of the SNWA intakes. Clark County’s 208 Water Quality Plan certified by EPA
and NDEP, regulates the quality and quantity of discharges from wastewater treatment
facilities that flow into Lake Mead. These discharges currently meet standards and will
do so into the future (Clark County, 1997). The SNWA is in the process of upgrading
its raw water treatment facilities and these state of the art facilities will be able to meet
ior
any treatment challenges from reduced reservoir levels caused bynter
I drought or declines
f the 9, 2017
from interim surplus alternatives.
pt. o
2

. De
ber
ion v Novem
3.5.3.3.1.2
Tributary Water at
jo NQuality on
Nava archived
in
Lower water surface elevations in Lake Mead could also impact the quality of tributary
cited 16864,
flows from the Las Vegas Wash, Virgin and Muddy rivers. These effects would be a
o. 14
Nchannels, and thus, longer travel times for influent streams. Potential
result of longer

effects on Lake Mead could include increased temperature due to warmer tributary
flows. Higher evaporative losses and greater concentration of salts and contaminants
may also occur in tributaries due to longer channels, leading to higher concentrations of
pollutants in the Las Vegas Wash, and potentially greater concentrations of
contaminants near the SNWA intakes. However, new riparian habitat development near
the mouths and in these tributaries would likely develop and would be expected to offset
impacts to tributary water quality. Restoration of the Las Vegas Wash wetlands will
trap surface and groundwater contaminants, cool return flows and further improve the
quality of return flows before it reaches Lake Mead.
3.5.3.3.2

Comparison of Baseline Conditions and Alternatives

Section 3.5.3.3.1, above, discussed the general water quality effects that may be
expected given reduced Lake Mead surface elevations and volumes. The following
sections compare predicted surface elevations, volume, and surface area of Lake Mead
under baseline and alternative conditions. This analysis is based on system modeling

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results; specifically the 50 percent (median) probability elevations, as shown on Figure
3.5-5.
Characteristics of Lake Mead (elevation, volume, surface area) under baseline and
alternative conditions are shown below for four selected years (i.e., years 2016, 2026,
2036 and 2050) within the modeled period, as shown in Table 3.5-6. A comparison of
the percentage difference between the alternatives and baseline conditions is shown in
Table 3.5-7. It should be noted that median elevations converge with the baseline
condition towards the end of the period of analysis, resulting in minimal differences
among the alternatives and baseline conditions in the year 2050.
3.5.3.3.2.1

Baseline Conditions

Baseline projections indicate a general trend of decreasing Lake Mead surface
elevations, volume and surface area over the period of analysis, as shown above on
Figure 3.5-5 and in Table 3.5-4. At the end of the interim surplus criteria period, 2016,
the median elevation for Lake Mead is 1162 feet msl, a reduction of 15 feet from the
surface elevation in 2002. The median baseline elevation in 2050 is 1111 feet msl for a
total reduction in the median elevation of 76 feet over the entire period of analysis. This
increased potential for lake level reductions would be expected to result r an increased
terio in
he Ineffects17 the SNWA
potential for declining water quality of Lake Mead and associated , 20 on
of t
9
ept. under baseline conditions.
intake (discussed in Section 3.5.3.3.1, above) over time mber 2
v. D

n
e
Natio d on Nov
o
ajAlternative
3.5.3.3.2.2
Basin Nav
States
ive
d in 64, arch
cite
8
Modeling of the Basin -16 Alternative indicates intermediate reductions in surface
. 14States
No
elevations, surface area and volume compared with baseline conditions in the year 2016
(when the largest differences among the alternatives are seen). The median elevation in
year 2016 under the Basin States Alternative is 1143 feet msl, or 1.6 percent lower than
baseline conditions in the same year, with reservoir volume approximate 12 percent
lower than baseline conditions and volume becoming slightly greater than baseline by
the year 2026 and slightly less than baseline in 2036. By the year 2050 no differences
between this alternative and baseline conditions are present.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

3.5-23

1143.3
1162.1
1145.5

Basin States

Flood Control

Six States

1124.7

1128.0

1124.7

1125.7

2026

2050
1110.6
1110.6
1110.6
1110.6

2036
1120.7
1120.4
1118.9
1120.5
16.0

17.9

15.8

17.9

2016

13.8

14.1

13.8

13.9

2026

13.4

13.2

13.4

13.4

2036

Volume
(maf)

12.5

12.5

12.5

12.5

2050

109.4

120.2

108.1

120.2

2016

99.3

100.7

99.3

99.8

2026

97.5

96.8

97.4

97.6

2036

Surface Area
(x 1000 acres)

-1.6%
0.00%
-1.4%
-2.7%
-2.7%

Flood Control

Six States

California

Shortage Protection

1117.6

1110.6

14.5

13.0

13.1

12.5

-0.2% 0.00% 0.00%

1.4%

-1.5% 0.00% 0.00%

-10.1

-0.7%

-0.8%

3.5-24

-0.3% 0.00% -19.6% -5.0%

-0.3% 0.00% -19.0% -6.5%

-2.2% 0.00% -15.4% -3.3%

-2.2% 0.00% -15.1% -3.9%

-0.5%

0.9%

-0.5

102.1

-0.1% 0.00% 0.00% -10.6% -0.7% 0.00% 0.00% -9.0%

0.2%

-0.1% 0.00% 0.00% -11.7% -0.7% 0.00% 0.00%

th

1116.4

Basin States

1131.2

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

1

California

0.00%

96.3

-1.3% 0.00%

-1.3% 0.00%

-0.2% 0.00%

-0.8% 0.00%

-0.2

95.9

or 96.3
Shortage Protection
1130.2 1117.9 1117.6 1110.6
14.4
13.2
13.1
12.5
101.7eri96.5
Int
e
of th 29, 2017
Values shown are median elevations (50 percentile) for each year group.
pt.
. De ember
v
ation on Nov
N
Table
vajo hived3.5-7
Modeled
in Na Comparisons of Alternatives to Baseline Conditions
rc
a
cited 16864,
Volume Change
Surface Area Change
1 Elevation Change
Alternative
o.20164 2026 2036 2050 2016 2026 2036 2050 2016 2026 2036 2050
N

1162.1

2016

Baseline Conditions

Alternative

Elevation
(feet above msl)

1

Table 3.5-6
Modeled Characteristics of Lake Mead Under Baseline and Alternative Conditions

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

93.6

93.6

93.6

93.6

93.6

93.6

2050

CHAPTER 3

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3.5.3.3.2.3

Baseline Conditions

Baseline projections indicate a general trend of decreasing Lake Mead surface
elevations, volume and surface area over the period of analysis, as shown above on
Figure 3.5-5 and in Table 3.5-4. At the end of the interim surplus criteria period, 2016,
the median elevation for Lake Mead is 1162 feet msl, a reduction of 15 feet from the
surface elevation in 2002. The median baseline elevation in 2050 is 1111 feet msl for a
total reduction in the median elevation of 76 feet over the entire period of analysis. This
increased potential for lake level reductions would be expected to result in an increased
potential for declining water quality of Lake Mead and associated effects on the SNWA
intake (discussed in Section 3.5.3.3.1, above) over time under baseline conditions.
3.5.3.3.2.4

Basin States Alternative

Modeling of the Basin States Alternative indicates intermediate reductions in surface
elevations, surface area and volume compared with baseline conditions in the year 2016
(when the largest differences among the alternatives are seen). The median elevation in
year 2016 under the Basin States Alternative is 1143 feet msl, or 1.6 percent lower than
baseline conditions in the same year, with reservoir volume approximate 12 percent
ior
lower than baseline conditions and volume becoming slightly greaterrthan baseline by
Inte 17
the year 2026 and slightly less than baseline in 2036. By f thyear 2050 0 differences
the e
no
pt. o er 29, 2
e present.b
between this alternative and baseline conditionsD
v. are
m

n
e
Natio d on Nov
ajoAlternative
3.5.3.3.2.5
Flood Nav
Control
ive
d in 64, arch
cite
8
Modeling of the Flood -16
. 14 Control Alternative produces similar surface elevations, surface
No
area, and volume compared with baseline conditions in the year 2016, with the
elevation, surface area and volume becoming slightly greater then baseline by the year
2026 and slightly less than baseline in 2036. By the year 2050 no differences between
this alternative and baseline conditions are present.
3.5.3.3.2.6

Six States Alternative

Modeling of the Six States Alternative indicates a Lake Mead surface elevation 1.4
percent lower and a volume 10.6 percent lower than baseline conditions in 2016. By the
year 2026 and for the remaining period of analysis, differences between baseline
conditions and this alternative are within one percent.
3.5.3.3.2.7

California Alternative

Modeling of the California Alternative indicates a volume of Lake Mead in the year
2016 that is 19 percent lower than baseline conditions, with the difference decreasing to
6.5 percent and 2.2 percent in the years 2026 and 2036, respectively.

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

3.5.3.3.2.8

Shortage Protection Alternative

Modeling of the Shortage Protection Alternative indicates similar changes in volume
reduction as the California Alternative throughout the period of analysis, with volume
19.6 percent lower than baseline conditions in 2016, 6.5 percent lower in 2026 and 2.2
percent lower in 2036.
3.5.3.3.2.9

Summary of Changes in Lake Mead Volume and Elevation

Tables 3.5-6 and 3.5-7 summarize modeled changes in Lake Mead surface elevation,
area, and volume under each of the alternatives as compared with baseline conditions.
With the exception of the Flood Control Alternative, each of the alternatives indicate an
increase potential for lower surface elevations, surface area and lake volume. These
difference are most pronounced in year 2016, the end of the interim surplus criteria
period. The greatest differences compared with baseline conditions are associated with
the California and Shortage Protection alternatives, with intermediate differences
indicated by the Basin States and Six States alternatives.
3.5.4 WATER QUALITY BETWEEN HOOVER DAM AND SOUTHERLY
r
INTERNATIONAL BOUNDARY
terio

n
the I , 2 17
. of contaminants0in the Lower
There have been concerns from the EPA and others pt
De about er 29
n v.SIB. ovemb there is little site specific
Colorado River between Hoover Dam and the
atio
N However,
ajo N USGS on study of mercury and other
data from this segment of thev
Na river. Ahived (1995)
contaminants foundd in and4, arc located in the Yuma Valley area concluded that
in fish 6 wildlife
cite 1 8
mercury is not a problem.6
14No.
The above study also indicates that selenium is also not a problem for fish and wildlife.
Selenium in Colorado River water in the Yuma Valley had a median value of less than
one micrograms per liter (μg/l). This research also confirms what other previous
selenium studies have concluded: selenium in the LCR and its biota remains below the
DOI level of concern of five μg/l. A 1986-1987 study by the USGS indicated a finding
of 3.4 μg/l or less for dissolved selenium at several sites in the Lower Colorado River
(USGS, 1988). Department of Interior’s Pre-reconnaissance Investigation Guides
(1992) reported similar findings of less than 3.4 μg/l in Colorado River water at Pilot
Knob. In the 1995 USGS study of the Yuma area, measured selenium in 18 water
samples averaged 1.72 μg/l, with a maximum of 8.0 μg/l and a minimum of less than
1.0 μg/l. Nine of the 18 measurement results were reported to be less than 1.0 μg/l.
Currently there are no state fish consumption advisories for mercury, selenium or any
other contaminants on the Lower Colorado River (Ketinger, 2000). Water quality
studies will continue in this segment of the river during the 15-year period of proposed
interim surplus criteria. None of the action alternatives are anticipated to increase
concentrations of contaminants beyond the noted limits.

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3.6 RIVERFLOW ISSUES
3.6.1

INTRODUCTION

This section considers the potential effects of interim surplus criteria on three types of
releases from Glen Canyon Dam and Hoover Dam. The Glen Canyon Dam releases
analyzed are those needed for restoration of beaches and habitat along the Colorado
River between the Glen Canyon Dam and Lake Mead, and for a yet to be defined
program of low steady summer flows to be provided for the study and recovery of
endangered Colorado River fish, in years when releases from the dam are near the
minimum. The Hoover Dam releases analyzed are the frequency of flood releases from
the dam and the effect of flood flows along the river downstream of Hoover Dam.
3.6.2

BEACH/HABITAT-BUILDING FLOWS

The construction and operation of Glen Canyon Dam has caused two major changes
related to sediment resources downstream in Glen Canyon and Grand Canyon. The first
is reduced sediment supply. Because the dam traps virtually all of the incoming
sediment from the Upper Basin in Lake Powell, the Colorado River is now released
from the dam as clear water. The second major change is the reduction in the high
ior
Inter 17 releases.
water zone from the level of pre-dam annual floods to the level of powerplant
f the 9, 20
Thus, the height of annual sediment deposition and pt. o hasr been reduced.
erosion
2
De

.
be
on v N em
atipreparation ovthe Operation of Glen Canyon
During the investigations leadingo N
on of
aj to the
Nav1995b),hived
Dam Final EIS (Reclamation,
in
arc the relationships between releases from the dam
c ted 16864,
and downstreamisedimentation processes were brought sharply into focus, and flow
4patterns designed . 1
Noto conserve sediment for building beaches and habitat (i.e.,

beach/habitat-building flow, or BHBF releases) were identified. The BHBF releases are
scheduled high releases of short duration that exceed the hydraulic capacity of the
powerplant. Such releases were presented as a commitment in the ROD (Reclamation,
1996e) for the Operation of the Glen Canyon Dam FEIS, at a then-assumed frequency
of one in five years.
In addition to the BHBF releases described above that exceed the hydraulic capacity of
the Glen Canyon Powerplant, the Operation of Glen Canyon Dam FEIS identified the
need for Beach/Habitat Maintenance Flow releases which do not exceed the hydraulic
capacity of the powerplant. These flows were designed to prevent backwater habitat
from filling with sediment and to reduce vegetation on camping beaches in years
between BHBFs. BHBF releases and Beach/Habitat Maintenance Flows serve as a tool
for maintaining a mass balance of sediment in Glen Canyon and Grand Canyon.

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3.6.2.1 METHODOLOGY
The frequencies at which BHBF releases from Glen Canyon Dam would occur under
baseline conditions and under operation of the interim surplus criteria alternatives were
estimated through the use of modeling as described in Section 3.3.
The model was configured to simulate BHBF releases by incorporating the BHBF
triggering criteria (contained in Section 3.6.2.2) into the Glen Canyon Dam operating
rules. The model was also configured to make no more than one BHBF release in any
given year.
3.6.2.2 AFFECTED ENVIRONMENT
Sediment along the Colorado River below Glen Canyon Dam is an important and
dynamic resource which affects fish and wildlife habitat along the river, creates
camping beaches for recreation, and serves to protect cultural resources. Except for
remnants of high river terraces deposited prior to the closure of Glen Canyon Dam, the
now limited sediment supply that exists along the river channel is affected by dam
operations.

ior

er
Since construction of Glen Canyon Dam, the measured suspended tsediment load (sand,
he In million tons per
017
silt, and clay) at Phantom Ranch (in the Grand Canyon)of t
pt. averages 11, 2
29
. De the Little
year. Most of this load comes from the PariavRiver andember Colorado River.
ion
N v
Flash floods from other side canyons at contributeo the sediment supply
ajo N alsoed on to
iv
(Reclamation, 1995b).in Nav
The suspended sediment load is sporadic in occurrence,
arch
ited 6864, releases and tributary inputs.
c
depending on Glen Canyon Dam
-1

14
No.

Beneficial sediment mobilization and deposition below Glen Canyon Dam depends on
the interaction of two occurrences for full effectiveness: the addition of sediment to the
river corridor and BHBF releases. The higher energy of BHBF releases mobilizes
suspended and riverbed-stored sand and deposits it as beaches in beach and shoreline
areas. Once a BHBF release has been made, additional sediment supply from tributary
inflows is needed before subsequent BHBF releases are fully effective in promoting
further beach and sandbar deposition along the river.
Subsequent to the ROD cited above, the representatives of the AMP further refined
specific criteria under which BHBFs would be made. The criteria provide that under
the following two triggering conditions, BHBF releases may be made from Glen
Canyon Dam:
1. If the January forecast for the January-July unregulated spring runoff into Lake
Powell exceeds 13 maf (about 140 percent of normal) when January 1 content is
greater than 21.5 maf; or
2. Any time a Lake Powell inflow forecast would require a monthly powerplant
release greater than 1.5 maf.

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Research concerning the relationships among dam operations, downstream sediment
inflow, river channel and sandbar characteristics, and particle-size distribution along the
river is ongoing.
3.6.2.3 ENVIRONMENTAL CONSEQUENCES
The effects of the interim surplus criteria alternatives on BHBF releases from Glen
Canyon Dam were analyzed in terms of the yearly frequency at which BHBF releases
could be made. Specifically, the frequency was indicated by the occurrence of one or
both of the triggering criteria cited above, during a calendar year. The following
discussion presents probability of occurrence under baseline conditions, and then
compares the probability of BHBF releases under each interim surplus criteria
alternative with the baseline conditions.
Figure 3.6-1 shows the probabilities that BHBF releases could be made under baseline
conditions and the action alternatives. The plots show that the probabilities will
decrease over the first decade to an irregular range of approximately 10 to 15 percent or
lower, which is maintained until a slight rising trend appears in the last 15 years of the
period of analysis. The trends result from the interaction of various factors, including
projected increases in depletions by the Upper Division states and the irequirements for
or
Inter 17
equalization of storage in Lakes Powell and Mead. The operational parameter most
f the 9 20
directly comparable to the plotted relationships is eptfuture median,water level of Lake
the . o
D level of er 2
Powell. As can be seen on Figure 3.3-6,on v.
the medianovembthe reservoir is projected to
ati
nN
recover somewhat in the last vajyears of the period of analysis. This correlates to the
15 o N
ed o
a
hiv
slight rise in BHBF d in N probabilities in the final 15 years.
release
, arc

cite 16864
14Table 3.6-1 summarizes the BHBF release probabilities during the interim period and
No.
the subsequent period to 2050, based on the data plotted in Figure 3.6-1. The table
reflects the higher average probability during the interim period than during the
succeeding period ending in 2050.
Table 3.6-1
Probabilities of BHBF Releases from Glen Canyon Dam
Percent of Time That Conditions Needed
for BHBF Releases Would Occur at Lake Powell
Period

Baseline
Condition

Basin
States
Alternative

Flood
Control
Alternative

Six States
Alternative

California
Alternative

Shortage
Protection
Alternative

Through 2016

15.9%

14.8%

15.9%

14.9%

13.0%

13.0%

2017-2050

13.5%

13.4%

13.5%

13.4%

13.2%

13.2%

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.6-3

0%
2000

10%

20%

30%

40%

50%

60%

70%

2005

2010

2015

2020

3.6-4

Year

2025

2030

2035

2040

ior
Inter 17
e
of th 29 0
Baseline Conditions , 2
pt. States Alternative
. De Basinmber
v
Flood
ation on Nove Control Alternative
Six States Alternative
jo N ved
Nava archi
California Alternative
in
Shortage Protection Alternative
ited 6864,
c
-1
14
No.

Figure 3.6-1
Lake Powell Releases
Probability of Occurrence of BHBF Flows

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Probability of Occurrence

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2045

2050

CHAPTER 3

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3.6.2.3.1 Baseline Conditions
During the interim period, the average probability under baseline conditions that BHBF
releases could be made in a given year is approximately 15.9 percent, which is
equivalent to about one year in six. During the subsequent period ending in 2050, the
average probability is approximately 13.5 percent, which is equivalent to about one year
in seven. The reduction in probability after 2015 under baseline conditions results from
the fact that with time, the Lake Powell water level will probably decline because of
increased Upper Basin depletions, as illustrated in Section 3.3. This water level decline
would gradually reduce the probability that the BHBF triggering criteria would occur.
3.6.2.3.2 Basin States Alternative
During the interim period, the average probability under the Basin States Alternative
that BHBF releases could be made in any single year is approximately 14.8 percent,
which equates to approximately one year in seven. During the subsequent period
ending in 2050, the average probability is approximately 13.4 percent, which is
equivalent to about one year in seven.

ior
Inter 17
f the
During the interim period, the average probability under the Flood9, 20 Alternative
pt. o er 2 Control
e
that BHBF releases could be made in any singleD isemb
n v.
ioin six. year v approximately 15.9 percent,
t
No
which equates to approximately jone year
o Na ed onDuring the subsequent period ending
va is approximately 13.5 percent, which is equivalent to
Na
in 2050, the average probability rchiv
ed in
itseven. 6864, a
about one year c
in
-1
o. 14
N
3.6.2.3.4 Six States Alternative
3.6.2.3.3 Flood Control Alternative

During the interim period, the average probability under the Six States Alternative that
BHBF releases could be made in any single year is approximately 14.9 percent, which
equates to approximately one year in seven. During the subsequent period ending in
2050, the average probability is approximately 13.4 percent, which is equivalent to
about one year in seven.
3.6.2.3.5 California Alternative
During the interim period, the average probability under the California Alternative that
BHBF releases could be made in any single year is approximately 13.0 percent, which
equates to approximately one year in eight. During the subsequent period ending in
2050, the average probability is approximately 13.2 percent, which is equivalent to
about one year in eight.

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CHAPTER 3

3.6.2.3.6 Shortage Protection Alternative
During the interim period, the average probability under the Shortage Protection
Alternative that BHBF releases could be made in any single year is approximately
13.0 percent, which equates to approximately one year in eight. During the subsequent
period ending in 2050, the average probability is approximately 13.2 percent, which is
equivalent to about one year in eight.
3.6.3

LOW STEADY SUMMER FLOW

3.6.3.1 AFFECTED ENVIRONMENT
During preparation of the Operation of Glen Canyon Dam FEIS, it was hypothesized
that steady flows with a seasonal pattern may have a beneficial effect on the potential
recovery of special status fish species down stream of Glen Canyon Dam. Accordingly,
development of an experimental water release strategy was recommended by the
Service to achieve steady flows when compatible with water supply conditions and the
requirements of other resources. The strategy included developing and verifying a yet
to be defined program of experimental flows which would include providing high
steady flows in the spring and low steady flows in summer and fall during water years
rior
when a volume of approximately 8.23 maf is released from he Inte
Glen Canyon Dam. This
t
017
strategy, commonly referred to as the low steady summerfflow program, was contained
pt. o er 29, 2
. De
in the Final Biological Opinion on the Operation of Glenmb
ion v Nove Canyon Dam (Service,
N t
December 1994c), and recognized in a ROD for the Operation of Glen Canyon Dam
vajo theved on
i
FEIS (USDI, 1996).d in Na
arch

cite 16864,
143.6.3.2 ENVIRONMENTAL CONSEQUENCES
No.

The ability to test the low steady summer flow release strategy at Glen Canyon Dam
according to the ROD could be affected by the implementation of interim surplus
criteria. This matter was investigated by analyzing the model releases from Glen
Canyon Dam to determine the probabilities at which minimum releases of 8.23 maf per
water year would occur.
Figure 3.6-2 shows the annual probabilities of minimum releases from Glen Canyon
Dam during the period of analysis. Note that the first year plotted is 2003, since 2003
would be the first complete water year (October 1, 2002 through September 30, 2003)
during the interim period. The plots show that the probabilities increase through 2023,
from approximately 20 to 25 percent to approximately 60 percent, which is maintained
until another increase to 67 percent occurs during the last 15 years of the analysis. The
trends result from the interaction of various factors that affect annual releases from Glen
Canyon Dam, including projected increases in depletions by the Upper Division states
and the requirements for equalization of storage in Lakes Powell and Mead.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.6-6

0%
2000

10%

20%

30%

40%

50%

60%

70%

2005

2010

2015

2020

3.6-7

Water Year

2025

2030

2035

2040

Shortage Protection Alternative

California Alternative

Six States Alternative

2045

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
Baseline Conditions
cite 168
Basin States Alternative
o. 14
Flood Control Alternative
N

Figure 3.6-2
Lake Powell Releases
Probability of Approximately 8.23 maf Annual Release

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Probability of Occurrence

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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Table 3.6-2 summarizes the probabilities that minimum releases would occur during the
interim period and the subsequent period to 2050, based on data plotted in Figure 3.6-2.
Probabilities are summarized by water year because releases from Glen Canyon Dam
are accounted for by water year under provisions of the LROC. The results indicate that
under baseline conditions, the probability of 8.23 maf annual releases from the dam is
approximately 38.2 percent during the interim period and 61.6 percent during the
subsequent period ending in 2050. The probabilities under all alternatives are similar to
those under baseline conditions after 2006. Under the Flood Control Alternative, the
probability is approximately the same as for baseline conditions, as shown on Table 3.62. The probabilities under the remaining four interim surplus criteria alternatives during
the interim period are one to two percent less than under baseline conditions. During
the subsequent period through 2050, the probabilities resulting from the remaining four
surplus criteria would be one to two percent higher than under baseline conditions.
Table 3.6-2
Probability of Minimum Glen Canyon Dam Releases
(Annual Releases of 8.23 maf)
Period
(Water
Years)

Baseline
Condition

Basin
States
Alternative

Flood
Control
Alternative

Six States
Alternative

California
Alternative

ior
Inter 17
Through
38.2%
36.3%
38.4%
36.2%he
35.8%
0
ft
2016
pt. o er 29, 2
e
v. D 61.9%b
m
2017-2050
61.6%
61.9%
61.6%
62.2%
ation on Nove
N
ajo is basedd
v
Note: The "water year" on whichNaaccounting hive extends from October 1 to September 30.
this
d in 64, arc
cite 168
14No.
3.6.4

Shortage
Protection
Alternative
36.3%
62.1%

FLOODING DOWNSTREAM OF HOOVER DAM

Under the BCPA, flood control was specified as the project purpose having first priority
for the operation of Hoover Dam. Subsequently, Section 7 of the Flood Control Act of
1944 established that the Secretary of War (now the Corps) will prescribe regulations
for flood control for projects authorized, wholly or in part, for such purposes.
The Los Angeles District of the Corps published the current flood control regulations in
the Water Control Manual for Flood Control, Hoover Dam and Lake Mead Colorado
River, Nevada and Arizona (Water Control Manual) dated December 1982. The Field
Working Agreement between Corps and Reclamation for the flood control operation of
Hoover Dam and Lake Mead, as prescribed by the Water Control Manual, was signed
on February 8, 1984. The flood control plan is the result of a coordinated effort
between the Corps and Reclamation; however, the Corps is responsible for providing
the flood control regulations and has authority for final approval. The Secretary is
responsible for operating Hoover Dam in accordance with these regulations. Any
deviation from the flood control operating instructions must be authorized by the Corps.

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This analysis addresses the flooding that occurs along the Colorado River below Hoover
Dam. The evaluation focuses on the change in the probability that various “threshold”
flows would be released from Hoover, Davis and Parker Dams. A threshold flow rate is
one at which flood damages have been found to begin to occur along the river. The
analysis is not limited to dam releases made expressly in connection with flood control
operation, but also includes releases made for water supply and power generation
purposes. For example, power generation requirements can cause releases from Hoover
Dam to exceed 19,000 cfs, with such releases being regulated in Lake Mohave
downstream. In addition, the analysis presents data on land use and anticipated flood
damages that were developed by the Los Angeles District Corps of Engineers in the
Review of Flood Control Regulations, Colorado River Basin, Hoover Dam, July 1982
(Corps, 1982).
3.6.4.1 AFFECTED ENVIRONMENT
Historical flows downstream of Hoover Dam have caused flood damages at various
points along the lower Colorado River. A key threshold level was established as a
result of flooding that occurred in 1983 when uncontrolled releases occurred over the
Hoover Dam spillways. The high Colorado River flows caused damages primarily to
encroachments in the Colorado River floodplain. In addition, several ilower thresholds
or
Inter subsections.
that are significant along various reaches are evaluated infthe e
th following017

t. o
9, 2
Dep Act) originated from
.(Floodwaymber 2
v
The Colorado River Floodway Protection Act
e
ation othe flood.
Nfollowing n Nov The Floodway Act called for
Congressional hearings held inajo
1983
d
av
hive
the establishment ofd ifederally declared floodway from Davis Dam to the SIB. The
anN
, arc
4
cite 168 either a 1-in-100 year river flow consisting of controlled
floodway is to accommodate6
41
releases and tributary inflow, or a flow of 40,000 cfs, whichever is greater. As
No.
discussed in Section 3.3.1, certain flood release rates from Hoover Dam are required
depending on flood flow into Lake Mead and the amount of available storage space.
Estimates of development in the flood plains below Hoover Dam were last made by the
Corps based on 1979 data (Corps, 1982). These data are presented in Table 3.6-3.
3.6.4.1.1 Hoover Dam to Davis Dam
Critical flood flows for the reach between Hoover Dam and Davis Dam are 19,000 cfs,
28,000 cfs, 35,000 cfs, 43,000 cfs, and 73,000 cfs.
3.6.4.1.2 Davis Dam to Parker Dam
The river is within levees for most of the reach from Davis Dam to Parker Dam.
Historical flood flows have caused damage to some of the bank protection. Minor
damage begins to occur at flows of 26,000 cfs.

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CHAPTER 3

Table 3.6-3
1
Development in Flood Plains Between Hoover Dam and SIB, 1979 Data
(Number of structures unless otherwise noted)
Flood Flow
(cfs)
100,000

Mobile
Homes

Residential

Commercial/

Public/

Industrial

Semipublic

Agriculture
(acres)

Recreation
5
Facilities

1,609

1,457

74

70

55,089

278

71,000

2

758

786

54

66

15,861

277

48,000

3

164

198

13

10

2,671

277

38,000

4

101

138

4

6

176

232

17

44

1

0

90

201

28,000
1

Corps of Engineers, Colorado River Basin Hoover Dam, Review of Flood Control Regulations. Final Report, July 1982.
Table C-1.
2
78,000 cfs at Needles.
3
50,000 cfs at Needles.
4
40,000 cfs at Needles.
5
Recreation facilities are primarily boat docks that would sustain significant damage with high flows.

ior
Inter 17
he
Critical flood flows for the reach between Hoover Dam of t Davis9, 20are 19,000 cfs,
pt. and er 2 Dam
De
b
28,000 cfs, 35,000 cfs, 43,000 cfs, and 73,000.cfs.
ion v Novem
at
on
ajo N
3.6.4.1.4 Davis Damin Nav Dam ived
to Parker rch
a
cited 16864,
The river is within levees for most of the reach from Davis Dam to Parker Dam.
14No.
3.6.4.1.3 Hoover Dam to Davis Dam

Historical flood flows have caused damage to some of the bank protection. Minor
damage begins to occur at flows of 26,000 cfs.
3.6.4.1.5 Parker Dam to Laguna Dam

Below Parker Dam, significant damage to permanent homes has occurred during
releases within the flood operation criteria. This area has been further developed since
the flood operations in 1983. Minor damage begins at 19,000 cfs along the Parker Strip
(the reach of river between Parker Dam and the town of Parker, Arizona). Backwater
regions, which function as wildlife refuges and recreational areas, accumulated
sediment, and in some cases, became isolated from the Colorado River. Historical flood
flows have also resulted in damage to infrastructure of government agencies.
3.6.4.1.6 Laguna Dam to SIB
Below Laguna Dam, the banks of the Colorado River are not protected. Historical flood
flows have resulted in significant damage to the banks. Associated increases of
groundwater level in the Yuma area have also resulted in some lands becoming water
logged and caused drains to cease functioning. During the scoping process for this

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DEIS, a letter from the Yuma County Water Users’ Association states that “[o]ur
landowners are harmed by such releases, particularly should the flood control releases
be required to go beyond the 19,000 cubic feet per second Hoover release level" (Pope,
1999). The letter indicates that a flood control release of 28,000 cfs or greater could
result in upwards of $200 million in damages to the Yuma area. Other injured parties
could include the City of Yuma, the County of Yuma, Cocopah Indian Tribe, the Gila
Valley, Bard Irrigation District, and the Quechan Indian Tribe.
Additional flows of concern include:
•

Laguna Dam south to Pilot Knob: 9,000 cfs is the threshold value. Flows of
10,000 cfs to 11,000 cfs impact leach fields of trailer parks located within
levees.

•

Pilot Knob to SIB: 15,000 cfs is a threshold value. Above that level, high
groundwater, localized crop damage and damage to the United States Bypass
Drain occur.

3.6.4.2 ENVIRONMENTAL CONSEQUENCES

rior

The effects of the interim surplus criteria on flood flows weree Inte by7
h analyzed determining
. of t r 2 reach 1
the probabilities that releases from Davis and Parker Dams would 9, 20or exceed
ept
e
certain flow rates that have been found to be v. D
for damages. In addition, the
n thresholdsemb
o
atireleases of various magnitudes would be made
Nov
analysis addressed the probabilitiesN
on
jo that
Nava archived flood control releases discussed in
from Hoover Dam corresponding to the required
in
,
cited 168 Hoover Dam. The release probabilities were determined
Section 3.3.1.2, Operation of64
from results ofNo. 14
river system modeling described in Section 3.3. The results of the
analysis are shown in Table 3.6-4.
The results portrayed on Table 3.6.3 show that except for the Flood Control Alternative,
the action alternatives would reduce the probability of flows at or above the damage
thresholds.
The Corps estimated the likely damage to development based on the 1979 land use data
(Corps, 1982). These data are presented in Table 3.6-5.
The data on direct, physical damages presented in Table 3.6-5 are based on
simultaneous flooding along all reaches of the river from Hoover Dam to the SIB. The
data show that damages increase much more rapidly than the size of the flow. For
example, a 48,000-cfs flow has 15 times the impact of a 22,000-cfs flow, while the flow
increases by only 2.2 times. A 48,000 cfs flow has a less than one-in-500 probability of
occurring in any one year, while a 22,000 cfs flow has a greater than one-in-20
probability of occurring in any one year under all alternatives.

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Table 3.6-4
Discharge Probabilities from Hoover, Davis and Parker Dams
Percent of Years With Flows Greater Than or Equal to Discharge
Release Point

Discharge
1
(cfs)

Baseline Basin States
Conditions Alternative

Flood
Control
Alternative

California
Alternative

Six States
Alternative

Shortage
Protection
Alternative

Years 2002 to 2016
Hoover Dam

19,000

20.8

18.8

21.2

16.3

18.6

16.9

Hoover Dam

28,000

7.5

7.2

7.7

5.5

7.1

5.8

Hoover Dam

35,000

2.1

2.0

2.1

1.6

2.0

1.7

Hoover Dam

40,000

0.2

0.2

0.2

0.2

0.2

0.2

Hoover Dam

73,000

0.0

0.0

0.0

0.0

0.0

0.0

Davis Dam

26,000

8.6

8.1

9.1

7.0

8.0

7.1

Parker Dam

19,500

10.4

9.4

11.3

7.8

9.3

8.0

14.6

14.1

14.9

13.9

14.1

13.8

3.8

3.6

0.9

0.8

0.2

0.1

0.0

0.0

4.6

4.5

5.7

5.6

Years 2017 to 2050
Hoover Dam

19,000

ior
Hoover Dam
35,000
0.9
1.7
0.9
0.8
Inter 17
he
. ft
9, 0
Hoover Dam
40,000
0.2
0.1
pt0.2o er 20.1 2
e
v. D vemb
Hoover Dam
73,000
0.0
0.0
0.0
ation on No0.0
ajo N iv4.6d
Davis Dam
26,000
4.8
5.0
4.4
e
Nav
d in 64, arch 5.7
Parker Dam
6.1
5.6
ite
c19,500 168 5.9
4.1
Average monthly No
discharge
Hoover Dam

28,000

4.0

3.8

4.2

3.7

1

Table 3.6-5
Estimated Flood Damages Between Hoover Dam and the SIB
1
(1979 level of development and 2000 price level )
Flood Flow (cfs)
100,000
2
71,000
3
48,000
4
38,000
22,000

Flood Damages
$201,000,000
$ 55,700,000
$ 9,210,000
$ 1,550,000
$
610,000

1

Corps of Engineers, Colorado River Basin Hoover Dam, Review of Flood Control Regulations.
Final Report, July 1982. Table C-5. Adjusted from June 1978 to March 2000 price level by
Consumer Price Index-all Urban Consumers. (June 1978 is 65.2, March 2000 is 167.8, Adjustment
factor: 2.57.)
2
78,000 cfs at Needles
3
50,000 cfs at Needles
4
40,000 cfs at Needles

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

3.7

AQUATIC RESOURCES

3.7.1

CHAPTER 3

INTRODUCTION

The analyses presented in this section consider two specific issues associated with
aquatic resources. These issues are potential effects to Lake Mead and Lake Powell
aquatic species habitat and potential effects to sport fisheries at Lake Powell, Lake
Mead, and the Colorado River between Lake Powell and Lake Mead. The interim
surplus criteria are not expected to result in any changes to aquatic resources below
Hoover Dam.
3.7.2

LAKE HABITAT

The primary lake habitats identified for potential affect within the project area include
Lake Powell and Lake Mead. Other reservoirs downstream of Lake Mead (Lake
Mohave and Lake Havasu) are not expected to be affected by the proposed interim
surplus criteria because operation of the system keeps lake levels at specified target
elevations to facilitate power generation and water deliveries (Reclamation, 2000).
Native Colorado River fishes have not fared well in the reservoirs. Non-native fish
ior
Inter well-established
species, which prey on and compete with native species, havee
f th become 017
in both lakes. While some native species may spawntwithin the 29, 2
p . o er reservoirs and others
De
b
have young that drift into the lakes, predation . competition is believed to eliminate
ion vand Novem
at precludes their survival and recruitment. A
young native fish from the reservoirs and ed on
ajo N
NavRiverrchiv is presented in Section 3.8, Special-Status
discussion of natived in
Colorado
a fishes
cite 16864,
Species.
43.7.2.1

No.

1

METHODOLOGY

Existing literature was reviewed to determine the historic and current status of fish
assemblages in Lake Powell and Lake Mead. Literature reviewed included recent
publications and draft documents on the operations at Lake Powell and Lake Mead,
biological assessments, fish management plans, and biological opinions. Investigation
into critical lake elevations, water quality, and temperature limits were made based on
the fish species known to inhabit these lakes, including the use of these lakes by
endangered species. Because no “threshold” lake elevations associated with significant
adverse effects on lake habitat were identified for any of the fish species, the use of
system modeling relied upon a comparison of general reservoir surface elevation trends
under baseline conditions and the alternatives, shown in Figures 3.3-6 and 3.3-13. A
qualitative analysis of potential lake habitat changes was made by comparing the
differences between lake level trends under baseline conditions and the various
alternatives.

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3.7.2.2

AFFECTED ENVIRONMENT

3.7.2.2.1

CHAPTER 3

Lake Powell

Aquatic habitat in Lake Powell is a result of the lake’s physical and geographical
characteristics. Lake Powell has a surface area of 255 square miles and contains up to
24.3 maf of active storage. At full pool, depth of the reservoir near the dam is 561 feet.
The thermocline (the boundary layer between a strata of colder and warmer water)
changes seasonally, but below approximately 150 feet deep, the cold hypolimnion (a
low oxygen, low light, deep water layer of the lake) is consistently maintained due to
thermal and chemical properties. Lake Powell exhibits a trophic gradient from the
shallow productive inflows where nutrients and sediments are delivered by rivers, to the
clear nutrient-poor water by the dam. As the reservoir gradually shallows moving away
from the dam, the depth and extent of the thermocline and hypolimnion change. Lake
elevations change from year to year depending on numerous factors, including Upper
Basin runoff. The clear water reservoir offers habitat beneficial to non-native fish.
Generally, the reservoir is oligotrophic (characterized by low dissolved nutrients and
organic matter); deep, clear, and low in chlorophyll abundance (NPS, 1996).
Non-native fish species became established by intentional and unintentional
ior
Inter 17
introductions. Largemouth bass and crappie populations were stocked initially and
0
f the 9 Both
subsequently proliferated to provide the bulk of the pt. o fisheries. , 2 species have
sport
e
r2
v. D v for be
declined in recent years due to lack of habitat structure emyoung fish. Filling,
o
ation oin changing habitat that eliminated most
N
fluctuation, and aging of the reservoir resulted n N
vajo hived
of the vegetation and favored different species. The habitat change led to the
in Na
arc
ited 6864,and striped bass, presently the two dominant predator
c
introduction of smallmouth bass
-1
o. 14
species in the reservoir, with striped bass being the most dominant. Threadfin shad
N
were introduced to provide an additional forage base and quickly became the
predominant prey species (NPS, 1996).
Other species common in Lake Powell include walleye, bluegill, green sunfish, carp and
channel catfish. Species that occur in the reservoir, but that are mainly associated with
tributaries and inflow, include fathead minnow, mosquitofish, red shiner and plains
killifish (NPS, 1996). Table 3.7-1 lists fish species present in the project area.
Native fish species were displaced by habitat loss and alteration associated with
construction and operation of mainstream dams and reservoirs, as well as competition
with and predation by introduced non-native species. Bonytail is the native species
believed to be in the most peril of imminent extinction because they are virtually
eliminated in the Upper Basin. Bonytail were reported in Lake Powell soon after
closure of Glen Canyon Dam; however, annual gill-net surveys conducted by the Utah
Department of Wildlife Resources have failed to produce any bonytail in the last 20
years.

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Table 3.7-1
Fish Species Present in the Project Area
Species
Black bullhead
Black crappie
Bluegill
Bluehead sucker
Bonytail
Brown Trout
Carp
Channel catfish
Colorado pikeminnow
Fathead minnow
Flannelmouth sucker
Green sunfish
Humpback chub
Largemouth bass
Mosquitofish
Northern pike
Rainbow trout
Razorback sucker
Red shiner
Roundtail chub
Smallmouth bass
Speckled dace
Spotted sculpin
Striped bass
Threadfin shad
Walleye

Scientific Name
Ictalurus melas
Pomoxis nigromaculatus
Lepomis macrochirus
Catastomus discobolus
Gila elegans
Salmo trutta
Cyprinus carpio
Ictalurus punctatus
Ptychocheilus lucius
Pimephales promelas
Catostomus latipinnis
Lepomis cyanellus
Gila cypha
Micropterus salmoides
Gambusia affinis
Esox lucius
Oncorhynchus mykiss
Xyrauchen texanus
Notropis lutrensis
Gila robusta
Micropterus dolomieui
Rhinichthys osculus
Cottus bairdi
Morone saxatilis
Dorosoma petenense
Stizostedion vitreum

Origin
Invading sport fish
Introduced sport fish
Invading sport fish
Native to Colorado River
Native to Colorado River
Introduced sport fish
Invading fish
Invading sport fish
Native to Colorado River
Invading forage fish
Native to Colorado River
Invading fish
Native to Colorado River
Introduced sport fish
Invading forage fish
Invading sport fish
Introduced sport fish
Native to Colorado River
Invading forage fish
Native to Colorado River
Introduced sport fish
Native to Colorado River
Native to Colorado River
Introduced sport fish
Introduced forage fish
Invading sport fish

ior
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cited 16864,
14No.

Other native species that may still persist in Lake Powell include the Colorado
pikeminnow and humpback chub. Although there have been no reports of Colorado
pikeminnow in the lake since 1977, they are believed to still inhabit the Colorado River
inflow area. Very few humpback chub have been found in Lake Powell and it is
presumed that they are not present in the lake at this time; however, unidentified chub
species were collected by seines and light traps in the Colorado River inflow area (NPS,
1996). Small numbers of razorback suckers have persisted in Lake Powell since the
closure of Glen Canyon Dam, occurring mainly near the inflow of the San Juan River.
Flannelmouth suckers are probably the only native fish to inhabit the main body of Lake
Powell in detectable numbers. However, there has been a declining trend in population
size and reproductive recruitment has not been documented. Additional discussion of
special-status fish species is included in Section 3.8.

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3.7.2.2.2

CHAPTER 3

Lake Mead

Lake Mead has a surface area of 245 square miles and a storage capacity of 26 maf.
Over two-thirds of the volume of Lake Mead remains at 55°F (13°C) throughout the
year, resulting in a constant, cool discharge at Hoover Dam (USBR, 1996d). At full
pool, depth of the reservoir near the dam is approximately 550 feet. Because of its
physical similarity to Lake Powell, the limnological characteristics of Lake Mead are
also similar. The thermocline changes seasonally and a cold hypolimnion is
consistently maintained due to thermal and chemical properties. Surface elevations
change from year to year depending on numerous factors, including Upper Basin runoff.
The clear water reservoir offers habitat beneficial to non-native fish.
Native fish species were displaced by habitat loss and alteration associated with
construction and operation of mainstream dams and reservoirs, as well as competition
and predation with introduced non-native species. Razorback sucker, federally listed as
an endangered species, is the only native species that maintains a remnant population in
Lake Mead (USBR, 1996a,b).
Non-native fish species became established by intentional and unintentional
introductions. Introduced fish species found in Lake Mead include largemouth bass,
ior
Inter carp (USBR,
striped bass, rainbow trout, channel catfish, crappie, threadfine
f th shad and017
1996). Bonytail populations are supported by specific. management,activities designed
pt o er 29 2
De
to re-establish this species in Lake Mohave. v.
emb
ion Remnantvpopulations of these species exist
at
No Havasu and groups such as the
on
jo Mohave and Lake
downstream of Lake Mead invLake N
Na a archived
n
Native Fish Wok Group (NFWG) and Lake Havasu Fishery Improvement Project
ted i
cicurrently6864, in activities conducted under Section 7(a)(l) of the
(HAVFISH) are
-1 engaged
o. 14
ESA to aid in the conservation and recovery of these species in the lower Colorado
N
River Basis (USBR, 1999).
Releases from Lake Mead are the predominant influence on inflows to two other
reservoirs, Lake Mohave and Lake Havasu. Operations at Lake Mead typically keep
lake elevations at the downstream reservoirs at specific target elevations to facilitate
power generation and water deliveries. The operation of Lake Mohave through 2002 is
anticipated to limit reservoir fluctuations as a measure to assure that potential impacts to
razorback sucker will be minimized during the spawning season (USBR, 1996).
3.7.2.2.3

General Effects of Reservoir Operation

Lake habitat in both Lake Powell and Lake Mead consists primarily of deep, clear, open
water habitats with a cold hypolimnion that is consistently maintained due to thermal
and chemical properties. The habitat found in these lakes is drastically different from
the riverine habitat that existed prior to the construction of the dams, and is more
suitable for non-native species than native species. Non-native fish species were
introduced into the lakes, and subsequently established naturally reproducing
populations. Habitat changes resulting from fluctuating lake levels have favored

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introduced species tolerant of the conditions and temperatures found in the lakes. These
species are able to reproduce in the lakes and are not expected to be affected by
fluctuating lake levels. In Lake Powell for example, striped bass have experienced
“unprecedented natural reproduction and survival” that allowed them to become “the
most numerous sport fish and dominate the fish community of Lake Powell” (NPS,
1996).
The ability of native species to adapt to the lake habitat is limited mainly by the
decreased survival of eggs and the lack of recruitment of young individuals into the
adult population. The primary reason for low recruitment of native fish is predation of
eggs and young by the established populations of non-native species. In some cases,
nutrition may also influence recruitment (Horn, June 2000).
3.7.2.3.

ENVIRONMENTAL CONSEQUENCES

There are no specific “threshold” lake levels that are definitive for evaluation of
potential impacts to lake habitat in Lake Powell or Lake Mead. Projections of Lake
Powell and Lake Mead surface the elevations are discussed in Sections 3.3.4.2 and
3.3.4.4, respectively. These reservoirs will continue to be subjected to varying inflows
and fluctuating surface elevations, primarily due to hydrologic conditions present in the
ior
Inter 17
watershed and increasing water use in the Upper Basin. Historically, reservoir
0
f the
conditions have resulted in lake habitat that is favorableo non-native2
pt. to er 29, species and
e
v. D
mb
unfavorable to native species. Becausetionprojected declines in reservoir surface
a the on Nove the normal operational range
elevation in both Lake Powell ajo Lake Mead are within
and N
d
Nav archivein substantial changes to lake habitat.
of fluctuations, theyd innot likely to result
are
,
3.7.3

cite 16864
4SPORT 1
No. FISHERIES

This section considers potential effects of the interim surplus criteria alternatives on
sport fisheries in Lake Powell, Lake Mead and below Hoover Dam. Potential effects on
recreation associated with sport fisheries are discussed in Section 3.9.5.
The sport fishery within the Colorado River corridor from Glen Canyon Dam to
Separation Canyon is not analyzed in detail in this FEIS because annual release patterns
from Glen Canyon Dam are determined in accordance with the 1996 ROD and are
monitored through the Glen Canyon Dam Adaptive Management Program. Through
this process, the effects of dam operations on downstream resources, including sport
fish, are monitored and studied. The results are used to formulate potential
recommendations on refinements to dam operations, to ensure that the purposes of the
Grand Canyon Protection Act are met.
The possibility of changes in river water temperature downstream of Hoover Dam was
also investigated. Reclamation conducted an analysis predicting water temperatures
downstream of Hoover Dam with a Lake Mead water surface elevation of 1120 feet msl
and a steady release of 62,000 cfs (30 percent higher than powerplant capacity). Under

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these conditions, the warmest temperature predicted was 58.5°F in late summer. The
midsummer discharge temperature was predicted to be 58.5°F (Reclamation, 1991).
Under actual conditions with a reservoir elevation of 1120 feet msl, however, maximum
discharge would be equal to the powerplant capacity of 49,000 cfs. At this lesser flow,
discharges would be cooler than the temperatures predicted in the analysis, since less
discharge water would be drawn from the warm upper portion of the reservoir than at
higher flows. Therefore, it is assumed that increases of release temperatures
corresponding to the median decline of lake levels under baseline conditions and the
action alternatives would result in temperatures less than those predicted in the 1981
analysis.
Staff from the Willow Beach Federal Fish Hatchery, located about 12 miles
downstream of Hoover Dam, reported that over the long term, river water temperatures
have typically ranged from 56°F to 58°F, with occasional lows of 54°F. Modeled
Hoover Dam discharges are not significantly different from those during periods when
water temperatures were measured by hatchery personnel. It is expected that the minor
changes in river water temperature described above would not be expected to adversely
affect fish populations or the sport fishery in the river below Hoover Dam. The
hatchery rears both trout and native fish. For native species, the hatchery warms the
r
river water with solar panels. The projected increase in river temperatures may be a
te io
Inarernot17
benefit to the hatchery’s native fish program. River temperatures
0 addressed
f the
pt. o er 29, 2
further in this section.
. De
b

nv
em
Natio d on Nov
vajo
e
in Na 4, archiv
d reviewed to determine the historic and current status of sport fish
Existing literaturee
cit was 1686
assemblages in Lake Powell and Lake Mead. Literature reviewed included recent
o. 14
Nthe status of sportfishing in both reservoirs, along with a review of
publications on
3.7.3.1

METHODOLOGY

water quality data including limnological reports and journal articles for information on
contaminants found within the lakes and in fish tissue. Potential effects on sport
fisheries identified herein are based on the analysis of lake habitat discussed in Section
3.7.2. Potential effects on sport fisheries are based on model output showing general
trends of reservoir surface elevations, river flow rates and temperature. No specific
threshold elevations or flows are used in the analysis.
3.7.3.2

AFFECTED ENVIRONMENT

Currently, Lake Powell and Lake Mead provide habitat for numerous species of
introduced (non-native) fish which support outstanding recreational sport fishing
opportunities. The fish species present in the GCNRA are listed in Table 3.7-1.
A similar species assemblage exists for Lake Mead. The two most common sportfish
species found in Lake Powell and Lake Mead are striped bass and largemouth bass.

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CHAPTER 3

Reservoir Sport Fisheries

The primary sport fisheries management challenge in the reservoirs is trying to stabilize
a striped bass population that reproduces beyond the limits of available forage. As a
result of unlimited striped bass reproduction, pelagic (open water) stocks of threadfin
shad upon which they prey have been decimated. Decimation of the shad population
then results in striped bass starvation. Reduction of striped bass numbers allows the
shad population to rebound from adult stocks residing in turbid, thermal refuges where
they are less vulnerable to striped bass predation. As shad reenter the pelagic zone in
large numbers, they are subsequently eaten by young striped bass who grow rapidly,
mature, and once again eliminate shad from the pelagic zone. This widely fluctuating
predator-prey cycle occurred during the 1990s and still occurs today.
Threadfin shad in Lake Powell exist in the northernmost portion of their range. Lower
lethal temperatures for shad are reported as 40°F to 41°F (4.5°C to 5°C). Shad currently
survive winters where water temperatures consistently range near the lethal limit by
seeking deep strata where the water temperature is warmer and stable. An additional
temperature reduction of even 2°F (1.0°C) may remove the thermal refuge and result in
loss of shad over winter. The absence of a pelagic forage fish would not eliminate
striped bass, which now subsist on plankton for the first year or two ofor but would
teri life,
eventually result in a permanently stunted striped bass population without 7
he In 201 quality sport
of t
ept. ber 29,
fishing value (NPS, 1996).
.D

nv
vem
Natio d on Nomuch the same manner as in Lake
jo
The sport fishery at Lake Mead has been managed in
Nava a the ive
inin many,of rchsame management challenges. The introduction
Powell and has resulted
cited forage 64
of threadfin shad as a4-168 species and striped bass as the main predator has produced
1
similar interactions between the two species.
No.
3.7.3.3

ENVIRONMENTAL CONSEQUENCES

3.7.3.3.1

Reservoir Sport Fisheries

The sport fishery in Lake Powell and Lake Mead is primarily based on the presence of
striped bass. Other sport fish found in the lakes include largemouth bass, catfish and
trout. Since the predator-prey relationship between striped bass and threadfin shad can
result in large variations of the striped bass population, stabilizing the population of
striped bass and maintaining the threadfin shad population is an ongoing challenge to
sport fish management in the lakes.
Although the occurrence of prey base fluctuations is more directly related to striped
bass populations, a thermal refuge for adult threadfin shad is critical. Under baseline
conditions and each of the alternatives, the challenge of stabilizing striped bass and
threadfin shad populations in the lakes will continue and may include the need to alter
the size or catch limit of striped bass or planting of fish from hatchery stock. All of the
other sport fish, with the possible exception of trout, are well-adapted to habitats found

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in the lakes and are largely unaffected by fluctuating lake levels and water temperatures.
Trout populations in the reservoirs are sustained by planting fish from hatchery stock.
3.7.3.3.2

Colorado River Sport Fisheries

The primary sport fish in the Colorado River between Glen Canyon Dam and the Lake
Mead inflow is rainbow trout. Natural reproduction of rainbow trout in the Grand
Canyon is dependent on cool water temperatures, access to tributaries for spawning and
continued availability of suitable main stem habitat. These variables are directly related
to patterns of flow releases from Lake Powell. Under baseline conditions and each of
the alternatives, an increase in the temperature of water released from Glen Canyon
Dam could occur if reservoir levels in Lake Powell fall below an elevation of 3590 feet
msl. The probability of elevations below 3590 feet msl is limited to the 10 percentile
rankings and is not projected to occur until approximately years 2018 to 2028. Water
releases from Glen Canyon Dam are controlled by operating criteria contained in the
1996 ROD and are monitored for compliance with the Grand Canyon Protection Act
through the Adaptive Management Program. As a result, Colorado River sport fisheries
would not be affected by the interim surplus criteria alternatives.

ior
Inter 17
0
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e
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ation on Nove
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cited 16864,
14No.

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3.8

SPECIAL-STATUS SPECIES

3.8.1

CHAPTER 3

INTRODUCTION

This section identifies potential effects of proposed interim surplus criteria to aquatic
and terrestrial species of concern and their habitat, from Lake Powell to the SIB.
Potential impacts to special-status species in Mexico are discussed in Section 3.16,
Transboundary Impacts. As discussed in Section 1.4, a considerable amount of
information pertinent to this analysis is available from various documents prepared by
Reclamation and the Service under NEPA and/or the ESA, and is incorporated by
reference.
Special-status species are species that are listed, or are proposed for listing, as
“threatened” or “endangered” under the federal ESA that may be present in the area
affected by the proposed action, and also include species of special concern to states or
other entities responsible for management of resources within the area of analysis. This
section contains a discussion of the life history requirements of each species, followed
by an analysis of potential impacts to the species and its habitat.
Reclamation is consulting with the Service (and NMFS) to meet itserior
t responsibilities
under Section 7 of the ESA on the effects of the proposedf action n federally listed
he I to 2017
o t
species. Reclamation prepared a biological assessment (BA)er 29,evaluates the
ept. b which
. D them
potential effects on listed species which imayv
at on occur in ve area from the headwaters of
No
N
Lake Mead to the SIB (Reclamation, 2000). Preliminary evaluation of the effects to
vajo hived on
Na
c
listed species whichd in be presentrin the Colorado River corridor from Glen Canyon
ite may 6864, a
c
Dam to the headwater of Lake Mead led to the conclusion that the interim surplus
14-1
o.affect any species. Therefore, this area was not addressed in the BA.
criteria would N
not
Refinements to the model used to predict future operations of Glen Canyon Dam for
this EIS indicated there would be a minor change in the frequency with which flows
recommended by the 1994 biological opinion concerning operation of Glen Canyon
Dam would be triggered. It was determined that this change may affect listed species.
The results of this analysis were provided to the Service in a November 29, 2000
memorandum as supplemental information to the BA, which is included in
Attachment S.
Potential impacts to special-status species occurring in Mexico are discussed separately
in Section 3.16, Transboundary Impacts. Specifically, Section 3.16 considers the
potential effects on the following species: desert pupfish, vaquita, totoaba,
Southwestern willow flycatcher, Yuma clapper rail, yellow-billed cuckoo, California
black rail, elf owl, Bell’s vireo, and Clark’s grebe. Although consultation on species
occurring in Mexico may not, as a matter of law, be required by the ESA, Reclamation
is also supplementing the BA to include information pertinent to federally listed species
from this analysis.

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CHAPTER 3

METHODOLOGY

Information on the affected environment and special-status species that may occur in
the analysis area was compiled based on review of the pertinent documents listed in
Section 1.4, available published and unpublished literature, and through personal
communication with agency resource specialists. Species’ distribution, range and
habitat requirements were reviewed. These requirements formed the basis for
compiling an initial list of plant, wildlife and fish species to be considered.
This analysis first discusses vegetative communities that exist throughout the analysis
area, from Lake Powell to the SIB. Potentially affected plant, wildlife and fish species
are then determined by considering hydrologic requirements and other habitat elements
important to the species, such as nesting or breeding habitat for birds and spawning and
rearing areas for fish. Species that are not known to be present in the analysis area, do
not depend on terrestrial or aquatic habitat associated with the area under consideration
or have a hydrologic connection are addressed briefly and removed from further
consideration. The analysis of effects to the remaining potentially affected plant,
animal and fish species and their habitat follows the section on the affected
environment.

ior
Inter 17
0
f the
pt. o er 29, 2
e
D
Vegetative communities within the analysis area are discussed, based on if they are
mb
n v.
atiohabitat) Nove the Colorado River (riverside
located alongside the reservoirs jo N
(lakeside
on or along
ve
Nava arare ithendidentified. The species are divided into
habitat). The special-status species ch
in
,
cited 168 wildlife and fish. Tables in this section list the species’
three main categories: plants,64
14common and scientific names and current status, and indicate if critical habitat has been
No.
3.8.3

AFFECTED ENVIRONMENT

federally designated. Following each table, the occurrence and requirements of the
species is provided. Species that would not be affected by the interim surplus criteria
are identified and removed from further analysis.
3.8.3.1

LAKE AND RIPARIAN HABITAT

A description of lakeside vegetation associated with Lake Powell and GCNRA is
provided below, followed by a description of vegetation associated with Lake Mead and
LMNRA (which includes Lake Mohave) and Lake Havasu. This section then describes
riverside habitat along the Colorado River corridor from Separation Canyon to the Lake
Mead delta and below Hoover Dam. Aquatic habitat is discussed in the previous
section on Aquatic Resources (Section 3.7).
3.8.3.1.1

Lakeside Habitat

Riparian and marsh vegetation around Lake Powell and Lake Mead is extremely
restricted because of the desert terrain that extends directly to the water’s edge
(Reclamation, 1999d), and the continuously fluctuating lake levels that precludes

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establishment of vegetation. Tamarisk or salt cedar (Tamarix ramosissima), a nonnative invasive shrub- to tree-like plant along the Lake Powell shoreline is still
becoming established and has not yet formed stable ecosystems. These communities
will probably attain some importance as insect and wildlife (particularly bird) habitat in
the future, and already provide habitat for fish during high lake levels when the plants
are inundated (NPS, 1987).
Small intermittent or seasonal streams occur in many of the side canyons of Lake
Powell. Fluctuations in lake levels may result in standing water in these side canyons
where riparian vegetation has become established. Dominant plants found in these
canyons include Fremont cottonwood (Populus fremontii), tamarisk, and cattail (Typha
sp.) (NPS, undated b). The vegetation within these side canyons has been altered by the
lake itself as a result of periodic inundation in association with fluctuating lake levels.
In areas where there are springs and seeps, cattail marshes may be found. The most
serious adverse influence on canyon and spring riparian zones associated with
intermittent or seasonal streams in the side canyons of Lake Powell is domestic and
feral livestock use (NPS, 1987).
The GCNRA also has many springs, seeps that are common in alcoves along the canyon
walls, and waterpockets located in canyons and uplands. These areas iare recognized for
or
Inter the 7
their significance as wetland habitats and as unique ecosystems within 01 desert (NPS,
f the
pt. o er 29, 2
1987).
De

v.
mb
tion
aalong thenwallsve the canyon support hanging
No of
The seeps that are common in ajo N
valcoves ed o
gardens. Hanging gardens are a ,specialized vegetation type and have a unique flora
in Na 4 archiv
ted 6water
associated withci
them. The 86 sources that support hanging gardens originate from
-1
o. 14
natural springs and seeps within the Navajo sandstone formation and are independent of
N
Lake Powell. This plant community is found at various elevations around Lake Powell
and is typically not affected by reservoir fluctuations. GCNRA hanging gardens are
characterized by Eastwood monkeyflower (Mimulus eastwoodiae), alcove columbine
(Aquilegia micrantha), Rydberg's thistle (Cirsium rydbergii) and alcove primrose
(Primula specuicola). None of these are special-status species at this time, although all
four are endemic to the Colorado Plateau. Maidenhair fern (Adiantum sp.) is the most
typical species in hanging gardens throughout the Plateau (Spence, 1992). Other
species typically associated with hanging gardens include maidenhair fern, golden
columbine (Aquilegia chrysantha) and scarlet monkeyflower (Mimulus cardinalis).

The highest concentration of habitat associated with Lake Mead in the LMNRA is
found in the Lake Mead and Virgin River deltas. Linear riparian woodlands may be
present along the shoreline of the Lake Mead delta following high water flows, and
associated sediment deposition and exposure. The sediment deposition and the
associated growth of riparian vegetation at the Lake Mead delta has occurred for
decades (McKernan, 1997). When lake levels decline, vegetation in the Lake Mead and
Virgin River deltas begins to establish on clay/silt deposits. The dynamic nature of
fluctuating lake levels and deposition of sediment in the Lake Mead delta is expressed

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as a change in plant species composition and relative abundance over time. In 1963,
tamarisk was the dominant tree species in the Lake Mead delta (McKernan, 1997). In
1996, habitat descriptions for Southwestern willow flycatcher study sites at the Lake
Mead delta reported 95 percent of the vegetation as willow or cottonwood with only
five percent as tamarisk (McKernan, 1997). An increase in sediment deposition in the
deltas followed by lower lake levels allows establishment of native riparian habitat if
the lowering of the lake is timed to match native seed dispersal. As such, conditions for
establishment of native vegetation at the Lake Mead delta have improved since 1963
allowing cottonwood and willow to become the dominant vegetation.
Germination of willows at the Lake Mead delta likely occurred in the spring of 1990 at
the approximate water surface elevation of 1185 feet msl (McKernan, 1997 and
Reclamation, 1998c). The water surface elevations in 1996 and 1997 were 1192 feet
and 1204 feet, respectively (Reclamation, 1998c). These higher lake levels inundated
willow habitat in the Lake Mead delta and the Lower Grand Canyon (McKernan, 1997).
Until 1998, the Lake Mead delta contained an extensive growth of riparian vegetation
principally composed of Goodding willow (Salix gooddingii) (McKernan, 1997). By
1999 the Lake Mead delta willow habitat was completely inundated. To a lesser degree,
these same effects may also be seen at the Virgin River delta. A higher delta gradient at
or
the Virgin River delta results in a shorter period of inundation at nteri(greater than 1192
I high 17
e
feet msl) lake levels (Reclamation, 1998c).
of th
, 20

9
pt.
. De ember 2
nv
Section VI of the BA (Reclamation, 2000) provides ov
atio
N additional information on
ajo N ived on
fluctuations in lake levels and development of riparian habitat at Lake Mead. It notes
Nav
ch
that determiningiexactly how64, aracres of riparian habitat that may be formed due to
d in
t
cate 168 many the proposed interim surplus criteria is
declining levels Lake Mead under
14No.
problematic. It further states that the majority of the Lake Mead shoreline does not

have the soil necessary to regenerate riparian habitat, and that riparian habitat created by
declining lake levels would most likely occur in four areas: Lake Mead delta, Virgin
River delta, Muddy River delta and the portion of the Lower Grand Canyon influenced
by Lake Mead. However, future wet hydrologic cycles, would inundate the newly
established riparian habitat.
Although higher lake levels may be detrimental to riparian vegetation at the Lake Mead
and Virgin River deltas, it may be beneficial to the development of riparian habitat in
the lower Grand Canyon downstream of Separation Canyon, and the Virgin and Muddy
rivers above Lake Mead (Reclamation, 1998c). Riparian habitat extends from the lake
deltas upstream into the lower Grand Canyon and Virgin River Canyon. Development
of riparian habitat in these canyons is directly dependent upon fluctuating lake levels
and periods of inundation in the canyons. Data collected on riparian vegetation from
1998 Southwestern willow flycatcher surveys (McKernan, 1999) indicate a welldeveloped riparian corridor composed primarily of willow (Salix spp.) and tamarisk that
forms extensive and continuous stands in some portions of the lower Grand Canyon.
Lower water levels in Lake Mead that expose sediments in the Lake Mead, Virgin River
and Muddy River deltas have the potential to benefit establishment of riparian habitat in

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these areas. However, lower water levels in Lake Mead do not benefit establishment of
riparian and marsh habitat in the lower Grand Canyon. In order for riparian and marsh
habitats to become established along the Colorado River in the lower Grand Canyon,
higher water levels in Lake Mead are necessary.
A few literature sources briefly examine influences of fluctuating lake levels on marsh
habitat at the Lake Mead and Virgin River deltas. In 1995, the Lake Mead delta
supported hundreds of acres of cattail and bulrush marsh (Reclamation, 1996a). This
vegetation type increased after a period of high flows from 1983 to 1986. Deposits
containing clay/silt sediments are necessary for the development of emergent marsh
vegetation (Stevens and Ayers 1993). Low water velocity sites, such as the Lake Mead
and Virgin River deltas, permit clay/silt particles to settle from suspension. These
deposits provide a higher quality substrate for seed germination and seedling
establishment than underlying sand because of their greater nutrient levels and
moisture-holding capacity. With the appropriate water regime (i.e., higher river flows
during winter with lower flows during summer), these sites are more likely to support
emergent marsh vegetation (Reclamation, 1995b). Marsh vegetation that develops
during low lake periods would be lost during periods of high lake levels; however, this
habitat is more likely than cottonwood/willow to reestablish as lake levels fluctuate
(Reclamation, 1996a). Marsh vegetation that develops during lowtlake levels is
ior
In er 17
important habitat for many species, particularly breeding f the
20
o birds.

,
t.
Dep mber 29
.2000) provides additional information on
nv
e
The interim surplus criteria BA (Reclamation,
Natio d on Novhabitat at downstream reservoirs
fluctuations in lake levels and development of riparian
ajo
ive
Nav
(Lake Mohave and Lake Havasu).aThe interim surplus criteria are not expected to
d in 64, rch
ite
affect levels of c downstream reservoirs as they would be continue to be regulated to
the 4-168
1
meet downstream .
No flood control, power generation and water delivery purposes.
3.8.3.1.2

Riverside Habitat

The riparian vegetation along the Colorado River is among the most important wildlife
habitat in the region. Though not common, springs can be found within the GCNRA in
intermittent drainages where they often support wetland plant communities. Between
Glen Canyon Dam and Lees Ferry, springs are created by several spontaneous, copious
flows from the lower canyon walls (NPS, 1987). The Water Resources Management
Plan and Environmental Assessment for the GCNRA speculates that this spring flow
originates from Lake Powell bank storage in the Navajo Sandstone (NPS, 1987), and
thus, this area could be affected by changes in Lake Powell surface levels. Overall,
lower lake levels are not likely to have any impacts on gardens around Lake Powell, but
may have some impacts on springs directly associated with Glen Canyon Dam and
extending downriver approximately two to three miles. In the lower canyon,
arrowweed (Pluchea sericea) and horsetail are common. Below Havasu Creek,
bermuda grass becomes the dominant ground cover at many sites (Reclamation, 1996a).

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Mesquite (Prosopis glandulosa) historically occurred on the broad alluvial floodplains
of the Colorado River on secondary and higher terraces above the main channel
(LCRMSCP, undated). It still is a dominant species above the scour zone through the
Grand Canyon (Ohmart et al., 1988; Turner and Karpiscak, 1980); however, tamarisk is
replacing mesquite in many areas along the Colorado River.
Catclaw acacia occurs along watercourses and other areas where a summer water supply
may be present (Barbour and Major, 1995; Brown, 1994; Holland, 1986; Sawyer and
Keeler-Wolf, 1995). This species occurs in both upland and riparian vegetation
associations (Reclamation, 1996a). Catclaw acacia in the Grand Canyon can occur with
Apache plume (Fallugia paradoxa), a typical constituent in the acacia-mesquite habitat.
It may also be found with desert broom (Baccharis spp), which is an obligate riparian
species that occurs in the cottonwood-willow habitat type (Turner and Karpiscak,
1980).
Two types of marsh plant associations have been identified along the Colorado River
(Stevens and Ayers, 1991). Marshes were historically found along oxbow lakes and in
backwater areas along the Colorado River. Cattails, bulrushes, common reed and some
less common emergent plants occur in marsh areas that develop on sediment deposits
containing about half clay/silt and half sand (Reclamation, 1995). erior

nt
7
the I
f surplus 9, 201may affect
In the lower Grand Canyon above Lake Mead, theept. o
interim
2 criteria
D
er
backwater marshes due to the changes inon v. levels.vemb changes in water levels
i water No These
at
on
could affect temperature and vajo water quality considerations, as well as the
other N
ived of the BA (Reclamation, 2000) discusses
Na
establishment of marshn
i vegetation. rSection V
a ch
citedmarsh,864,
historic and existing -16 backwater and aquatic habitat on the lower Colorado River
14
below Hoover, Davis and Parker dams.
No.
3.8.3.2

SPECIAL-STATUS PLANT SPECIES

The list of special-status plants in Table 3.8-1 below is based on documented or
potential occurrence within vegetation communities of the Glen Canyon National
Recreation Area (GCNRA), Lake Mead National Recreation Area (LMNRA) and the
Colorado River corridor in the lower Grand Canyon. No special-status plant species
were identified for analysis below Hoover Dam. Nineteen plant species were removed
from detailed consideration, as discussed in the next section. Four species could be
affected by interim surplus criteria alternatives and are considered further.

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Table 3.8-1
Special-Status Plant Species Potentially Occurring Within the Area of Analysis
Common Name

Scientific Name

Alcove bog orchid
Alcove daisy
Alcove deathcamas
Barrel cactus

Habenaria zothecina
Erigeron zothecinus
Zigadenus vaginatus
Ferrocactus acanthodes
var. lecontei

Brady’s footcactus
Canyonlands sedge

Pediocactus bradyi
Carex scirpoidea
var. curatorum
Astragalus geyeri
var. triquetrus
Camissonia specuicola
ssp. Hesperia

Geyer’s milkvetch

1

Grand Canyon evening1
primrose
Hole–in-the-Rock prairie
clover
Jones cycladenia

Dalea flavescens

Status
Federal Species of Concern
Federal Species of Concern
Federal Species of Concern
Northern Nevada Native Plant Society
(NNNPS) Watch List species and
Listed as Sensitive by the Service
(Intermountain Region)
Federally Listed Endangered
Federal Species of Concern
Federal Species of Concern;
Nevada Critically Endangered
Federal Species of Concern
Federal Species of Concern

Ute ladies’ tresses
Virgin River thistle

Cycladenia humilis
var. jonesii
Erigeron kachinensis
Arctomecon californica
Carex specuicola
Rubus neomexicana
Perityle specuicula
Penstemon bicolor
ssp. Roseus
Imperata brevifolia
Cladium californicum
Eriogonum viscidulum
Psorothamnus thompsoniae
var. whittingii
Spiranthes diluvialis
Cirsium virgenense

Western hophornbeam

Ostrya knowltonii

Federally Listed Threatened

ior
t Concern
Inofer 17
Kachina daisy
Federal Species
f the 9, 20
1
Nevada
Las Vegas bear poppy
pt. o Listed Critical Endangered
De Federallyber 2Threatened
Navajo sedge
n v.
ovem Listed
Natio d on NFederal Species of Concern
New Mexico raspberry
vajo
e
Rock Daisy
Federal Species of Concern
in Na 4, archiv
d
te
86
Rosy bicolored ci
Federal Species of Concern
16
beardtongue
. 14No
Satintail grass
Federal Species of Concern
Sawgrass
1
Sticky buckwheat
Thompson’s indigo-bush

1

Federal Species of Concern
Federal Species of Concern
Federal Species of Concern
Federally Listed Threatened
Federally Listed Species of Concern;
Arizona Salvage-restricted,
Protected Native Plant
Federal Species of Concern

Species with the potential to be affected by the interim surplus criteria that are considered further.

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CHAPTER 3

Plant Species Removed from Further Consideration

This section discusses the reasons for eliminating certain special-status plant species
from detailed consideration.
Special-status plant species that occur in hanging gardens at GCNRA include alcove
bog orchid, alcove daisy, alcove deathcamas, canyonlands sedge, Kachina daisy,
Navajo sedge, New Mexico raspberry, sawgrass, western hophornbeam and Virgin
River thistle. The water source for these species comes from seepage from the Navajo
sandstone that would not be affected by hydrologic changes associated with interim
surplus criteria.
Barrel cactus, Brady’s footcactus, rosy bicolored beardtongue, Jones cycladenia and
Thompson’s indigo-bush are desert species. This habitat type and associated plant
species would not be affected by interim surplus criteria.
Hole-in-the-Rock prairie clover occurs in the Hall’s Creek and Escalante drainages in
the GCNRA, which would not be affected by hydrologic changes associated with the
interim surplus criteria.

ior

ter
Rock daisy occurs at Cedar Mesa in GCNRA, growing in sandstone along 7 margins
the
he In be0affected by
of an ephemeral stream channel at the canyon bottomt. of would29, 2 1
that t
not
Dep mber
interim surplus criteria.
n v.
e
Natio d on Nov
ajo Wilson’s Creek in the GCNRA, an area that would
Satintail grass occurs within lower rchive
Nav
d in surplus a
not be affected cite
by interim6864, criteria.
-1
o. 14
N
Sawgrass has been found in the riparian zone of Alcove Canyon in Grand Canyon
National Park, and in the riparian zone of Garden Canyon on the cliffs above Lake
Powell. These riparian zones would not be affected by interim surplus criteria.

Ute ladies’ tresses occur in moist to wet meadows along perennial streams at elevations
between 4,300 and 7,000 feet msl. These occurrences are above those elevations that
occur within the area under consideration. As such, this species would not be affected
by interim surplus criteria.
Virgin River thistle occurs on sandy or gravelly alkaline slopes and washes and around
saline seeps, alkaline springs or stream terraces. It occurs between elevations of 1968
and 6562 feet msl, and is associated with Mojave mixed scrub habitat. This habitat type
would not be affected by interim surplus criteria. As such, this species would not be
affected by interim surplus criteria.
3.8.3.2.2

Plant Species Considered Further

Geyer’s Milkvetch - Geyer’s milkvetch is known to occur along the shoreline of Lake
Mead and is associated with stabilized sand dunes and sandy soils. Population trends

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have not been well documented for Geyer’s milkvetch. Germination may be tied to
rainfall, and poor seed production and insect infestations may contribute to the limited
distribution and/or small population sizes observed for this variety (Mozingo and
Williams, 1980). Some populations have been directly affected by rising water levels at
Lake Mead (i.e., Middle Point). Additional causes of decline for this taxon may include
shoreline recreation, trampling and grazing by burros and livestock, off-road vehicle
use, and utility corridors (Niles et al., 1995).
Threats to Geyer’s milkvetch in the study area have not been well defined. This variety
may be potentially threatened by: 1) loss of habitat from inundation and rising water
levels at Lake Mead; 2) invasion of shoreline (beach) habitat by other plant species (i.e.,
tamarisk and arrowweed); and possibly 3) trampling and grazing by burros. Geyer’s
milkvetch occurs further back from the shoreline and may be less affected by these
factors (E. Powell, 2000). Shoreline recreation does not currently appear to be a major
threat to this species because the beaches where it occurs do not receive heavy
recreational use. In addition, the species typically flowers and sets seed prior to the
beginning of heavy use periods at Lake Mead (Niles et al., 1995; E. Powell, 2000).
However, rising lake levels may potentially affect this species directly by inundation of
plants or indirectly through inundation of suitable habitat.

ior
Inter is17clustered
Grand Canyon Evening Primrose - Grand Canyon evening e
of th primrose 0 a
pt.yelloweor 29, 2at anthesis
herbaceous perennial plant with small flowers .thate
D are
b r white
ion v aging. The
(flowering), but may turn to pink or lavender withNovem Grand Canyon evening
Nat
primrose occurs on beachesavajoor near ed on stem Colorado River in the vicinity
along
iv the main
N
of Separation Canyon iand downstream of Diamond Creek where available beach habitat
d n 64, arch
cite
is exposed (Brian, 2000 168Phillips, 2000). This species is likely adversely affected
. 14- and
when beaches No disturbed through erosion or deposition of sediments during flood
are
events. Some degree of flooding occurs seasonally as the result of increases in sidechannel inflows during rainfall events. Additional flood flows result from periodic
BHBF releases from Glen Canyon Dam. The degree to which flooding adversely
affects this subspecies and which water levels are detrimental to the plants and its
habitat is unknown. However, the amount of beach habitat in the Grand Canyon has
decreased under post-dam conditions, and the remaining habitat is often invaded by
riparian vegetation (Schmidt et al., 1998). Because this subspecies is found on good
camping beaches, particularly in the lower portion of the Grand Canyon, it may also be
adversely affected by disturbance associated with recreational beach use; however, this
potential effect is not related to the interim surplus criteria.
Las Vegas Bear Poppy - Las Vegas bear poppy is a short-lived perennial species,
occurring along the lower levels of the Lake Mead shoreline (E. Powell, 2000). This
plant occurs on gypsum soils below the high water line of Lake Mead (1225 feet msl)
on sloping flats. Little is known about the life cycle of the Las Vegas bear poppy, and
populations vary in a “boom or bust” pattern (E. Powell, 2000). This species would
benefit from lower water levels at Lake Mead, and could be adversely affected by

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increases in water levels although timing of water fluctuations and associated effects to
this species are unknown.
Sticky Buckwheat - Sticky buckwheat is found primarily along the Overton Arm of
Lake Mead (Reveal and Ertter 1980, Niles et al., 1995). Smaller, potentially significant
populations occur in the vicinity of Overton Beach, along the Virgin River Valley, and
along the Muddy River. Major threats to sticky buckwheat at Lake Mead include: 1)
loss of habitat from inundation and rising water levels at Lake Mead; 2) invasion of
shoreline (beach) habitat by other plant species (i.e., tamarisk and arrowweed); and
possibly three) trampling and grazing by burros. Shoreline recreation does not currently
appear to be a major threat to this species because the beaches where it occurs do not
receive heavy recreational use. In addition, the species typically flowers and sets seed
prior to the beginning of heavy use periods at Lake Mead (Niles et al., 1995). This
species would benefit from lower water levels at Lake Mead, and could be adversely
affected by increases in water levels.
3.8.3.3

SPECIAL-STATUS WILDLIFE SPECIES

Special-status wildlife species with the potential to occur within the area under
consideration in the United States are listed in Table 3.8-2. Two invertebrate, two
ior
Inter and two
amphibian, and one reptile species are of concern. Eleven bird species 017
f the
pt. o on er 29, 2
mammals are of concern. A number “1” after .the e
D species b the table indicates the
ion v Nosurplus
species has the potential to be affected by the interim vem criteria alternatives, and is
Nat d on
therefore assessed in more detail.o
vaj
a
ive

in N
rch
ited 6864, a
c
-1
o. 14
N

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Table 3.8-2
Special-Status Wildlife Species Potentially Occurring Within the Area of Analysis
Common Name

Scientific Name

Status

Invertebrates
MacNeill’s sootywing skipper

Hesperopsis gracielae

Federal Species of Concern

Kanab ambersnail

Oxyloma haydeni kanabensis

Federally Listed Endangered;
Arizona Wildlife of Special
Concern

Amphibians
Northern leopard frog

Rana pipiens

Arizona Candidate for Listing

Relict leopard frog

Rana onca

Nevada State Protected;
Arizona Wildlife of Special
Concern

Kinosternon sonoriense
sonoriense

California Species of Special
Concern

Falco peregrinus anatum

California Endangered;
Nevada State Protected and
Endangered
California Endangered

Reptiles
Sonoran mud turtle
Birds
American peregrine falcon

Arizona Bell’s vireo

1

Vireo bellii arizonae

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
1
Laterallus jamaicensis
California black rail
jo N
coturniculus
Nava archived
in
1
Aechmophorus clarkii
Clark's grebe
cited 16864,
4.1
1
Accipiter cooperii
California Species of Special
Cooper's hawk No
Bald eagle

1

Haliaeetus leucocephalus

Federally Listed Threatened;
California Endangered;
Nevada State Protected and
Endangered
Federal Species of Concern;
California Threatened
Arizona Wildlife of Special
Concern

Micrathene whitneyi

Concern
California Endangered

Gilded flicker

Colaptes chrysoides

California Endangered

Southwestern willow
1
flycatcher

Empidonax traillii extimus

Federally Listed Endangered
(critical habitat designated);
California Endangered;
Nevada State Protected
Federally Listed Endangered;
California Threatened
Federally Proposed Endangered;
California Endangered;
Nevada State Protected

Elf owl

1

1

1

Rallus longirositris yumaniensis

Yuma clapper rail

Western yellow-billed cuckoo

1

Coccyzus americanus

Mammals
Colorado River cotton rat

Sigmodon arizonae plenus

Occult little brown bat

Myotis lucifugus occultus

1

Federal Species of Concern;
California Species of Special
Concern
Federal Species of Concern;
California Species of Special
Concern

Species with the potential to be affected by the interim surplus criteria that are considered further in this analysis.

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CHAPTER 3

Wildlife Species Removed from Further Consideration

The Kanab ambersnail occurs in semi-aquatic habitat associated with springs and seeps.
In the Grand Canyon, Kanab amber snail were originally known to occur only at
Vasey’s Paradise, a large perennial spring. As part of an effort to recover the species,
Kanab amber snails were translocated from Vasey’s Paradise to three other locations.
One of the criteria used to select these sites was that it be above the level of any
potential future flood flows past Glen Canyon dam. These populations would not be
affected by the adoption of interim surplus criteria. Reclamation has consulted with the
Service on the effects to the Vasey’s Paradise population from the operations of Glen
Canyon Dam. The resulting biological opinion (USFWS, 1996) continues to be
implemented and will not be affected by the proposed action. There will be no effect
from the adoption of interim surplus criteria.
The northern leopard frog is known to occur in association with a spring at one site
below Glen Canyon Dam. The population was monitored before and after the 1996
BHBF and found to persist under these flows. This species receives consideration
under the Glen Canyon Dam AMP (see Section 3.2.2). The minor changes to
operations of Glen Canyon due to adoption of the interim surplus criteria are not
expected to affect the northern leopard frog.
erior

Int
0
f the several17
o
Historically, the relict leopard frog (Rana onca) was known from 9, 2 locations
ept. ber 2
D
along the Virgin river, and from the Overtonv. of ovem
to north
n
atiothe arm N Lake MeadMeadow of St. George,
N
n River and
o
Utah. This species was also known from ed Muddy
Valley Wash
vajo
v
in Nevada, northwest of the Overtonchi This species was thought to be extinct, but
in Na 4, ar Arm.
cited 1 of 6
was rediscovered at three 6851 potential habitat sites surveyed in 1991. Surveys
4conducted for No. 1
relict leopard frog included potential habitat within the historical range of
the species (Bradford and Jennings 1997). There are confirmed sightings of this species
at springs about two miles (3.2 km) west of Stewarts Point on the Overton Arm of Lake
Mead. A fourth population of leopard frog on the Virgin River near Littlefield, Arizona
is within the range of the lowland leopard frog (R. yavapaiensis) and is still awaiting
additional studies to confirm its taxonomic status. Other unconfirmed sightings are on
the Virgin River near Littlefield, Arizona and about four km (2.5 miles) downstream
from Hoover Dam.
In general, leopard frogs inhabit springs, marshes, and shallow ponds, where a yearround water supply is available. Emergent or submergent vegetation such as bulrushes
or cattails provides the necessary cover and substrate for cover and oviposition
(Jennings et al., 1994). Suitable aquatic habitat, as well as, adjacent moist upland or
wetland soils is required by the relict leopard frog. In addition, dense herbaceous cover
and a canopy of cottonwoods or willows characterize habitat for this species.
The relict leopard frog populations located near the Overton Arm of Lake Mead are
associated exclusively with geothermally influenced and perennial desert spring
communities. Because the known populations are currently confined within a five-mile

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(8km) area (Bradford and Jennings 1997), they are susceptible to extirpation from
localized impacts. Threats to this species include habitat destruction, lowering of the
water table, and predation by introduced bullfrogs (AGFD, 1996; AGFD 1998).
The known occurrences of relict leopard frogs are in association with springs that will
not be affected by the interim surplus criteria alternatives being considered. If
additional emergent marsh vegetation develops at the Lake Mead and Virgin River
deltas as the result of lower lake levels, it may provide potential habitat for the relict
leopard frog. However, predation by introduced fishes and bullfrogs may preclude
occurrence of the leopard frogs in these areas. Reclamation concludes that the interim
surplus criteria do not have the potential to affect the relict leopard frog.
MacNeill’s sootywing skipper is a butterfly found along the Colorado River from
southern Utah and Nevada to Arizona and southeastern California (Reclamation,
1996a). Confirmed records of this species are reported for the Arizona counties of
Mohave, La Paz, Yuma, Yavapai, Maricopa and Pinal. The MacNeill’s sootywing
skipper is also present in San Bernardino, Riverside and Imperial counties in California.
This species also occurs along the Muddy River above Lake Mead (Austin & Austin,
1980).

erior

Int
The larval host plant for MacNeill’s sootywing skipper is quailbrush (Atriplex
f the and2017 dense
lentiformis). Quailbrush is the largest salt bush found .in Arizona 9, forms
pt o
. DeRivermber 2 and Emmel, 1973).
thickets along the drainage system of theon v
Colorado
e (Emmel
Nati located in ov
n N alkaline soil areas with adequate
Quailbrush is associated withvajo
a floodplains ed o
water resources (KearneyN Peebles, 1951). Specific surveys for this species and
in and 4, archiv
cited not 86
larval host plants have -16been conducted in the lower Grand Canyon; however, the
14
documented occurrence of MacNeill’s sootywing skipper along the Muddy River above
No.
Lake Mead indicates there is a likelihood of occurrence in the lower Grand Canyon.
Suitable habitat for this species likely requires stands of more than one host plant (W.
Wiesenborn, 1999). Although this species occurs in the area of analysis, the host plant
occurs on alluvial floodplains and has little potential to be affected by the alternatives
considered for the interim surplus criteria.
Lake Powell and Lake Mead provide breeding and wintering habitat for American
peregrine falcons. The peregrine falcon breeds at sites on Lake Mead, and the upper
portion of Lake Mohave. Wintering and breeding peregrines are also found around
Lake Powell, with an estimated 50 breeding areas (Interior, 1995), and 19 wintering
territories (Hetzler, 1992a). Based on historical data, the average height above water of
peregrine nests at GCNRA is approximately 460 feet (141 meters), with average cliff
heights of 630 feet (193 meters) (Hetzler 1992a, Hetzler 1992b). These data include
nest sites in Glen Canyon immediately below the Glen Canyon Dam as well as sites on
Lake Powell. Glen Canyon Dam operations have resulted in increased riparian
vegetation which supports a larger population of passerines and increased the food base
for peregrine falcons.

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Existing and potential American peregrine falcon breeding habitat also occurs in the
Grand Canyon between Glen Canyon Dam and Lake Mead and in Black Canyon, (south
of Lake Mead). Because their nesting sites are well above the water and their food base
has increased, peregrine falcons would not be affected by hydrologic changes associated
with the interim surplus criteria and have been eliminated from further analysis.
The Sonoran mud turtle, Colorado River cotton rat, and occult little brown bat were
removed from further consideration because there are no known occurrences in the
analysis area.
3.8.3.3.2

Special-Status Wildlife Species Considered Further

Arizona Bell’s Vireo - The Arizona Bell’s vireo (Vireo bellii arizonae) is distributed
throughout the river systems of the Southwest desert and have been documented in the
Virgin and Muddy rivers, and the lower Colorado River. Since 1900, populations of
this subspecies of Bell’s vireo have declined along the lower reaches of the Colorado
River, where it is now a rare, to locally uncommon, summer resident from Needles
south to Blythe (Brown et al., 1983; Zeiner et al., 1990a; Rosenberg et al., 1991). Since
the completion of Glen Canyon Dam in 1963, the Bell’s vireo has expanded its range
eastward into Grand Canyon National Park (Brown et al., 1983). Anrextensive riparian
ior
Inte 17
scrub, that has developed along the Colorado River in thefGrand Canyon largely
the
0
pt. o er 29 2
composed of tamarisk and willow, supports a significant population,of Bell’s vireo
e
b
v. D
(Brown et al., 1983). The Grand Canyon population ofem vireo is regionally
ation on Nov Bell’s
oN
important due to the substantial decline ofed subspecies at lower elevations. The
this
avaj
NArizona rchiv vireo may potentially be affected by the
inby 4, a Bell’s
riparian habitat utilized
ited
6
interim surplusc
criteria.-168
4

No.

1

Bald Eagle - The bald eagle historically ranged throughout North America except
extreme northern Alaska and Canada and central and southern Mexico. In 1978, in
response to lowering population and reproductive success, the Service listed the bald
eagle throughout the lower 48 states as endangered except in Michigan, Minnesota,
Wisconsin, Washington and Oregon, where it was designated as threatened (43 FR
6233, February 14, 1978). In 1982, a recovery plan was developed specifically for the
southwestern bald eagle; the geographic boundary includes southeast California within
10 miles of the Colorado River or its reservoirs. The bald eagle population has clearly
increased in number and expanded its range since it was listed. This improvement is a
direct result of the banning of DDT and other persistent organochlorines, habitat
protection, and from other recovery efforts (60 FR 36001, July 12, 1995). On August
11, 1995, FWS reclassified the bald eagle from endangered to threatened in the lower
48 states. (60 FR 133, pg. 3600, August 12, 1995).
Reclamation’s 1996 BA concluded that its Lower Colorado river operations and
maintenance activities are not likely to adversely affect the food resources, foraging
opportunities, or the nesting habitat of the bald eagle. Based on data from bald eagle
winter counts conducted by the AGFD since 1992, eagles are not considered rare within

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the project area. Wintering birds are expected to continue using the river and most
likely will congregate where food resources are plentiful and excessive disturbance
from recreation can be avoided. The 1996 BA also cites studies by Hunt et al., (1992)
that conclude reservoirs and dams did not appear to have a negative effect on bald eagle
reproduction. River operations and maintenance may affect establishment of newly
regenerated cottonwood/willow stands that could provide future nesting and perching
substrate for eagles. However, as documented in Hunt et al. (1992), bald eagles can
successfully nest on other substrates (cliffs, pinnacles). Reclamation’s ongoing native
riparian plant restoration program has the potential to increase available tree nesting and
perching habitat along the river. No evidence exists to suggest that the food resources
available in the reservoirs and river are limiting nesting. Because of the minor changes
to the operation of Glen Canyon Dam and the minor hydrologic changes in the
reservoirs and along the river, Reclamation determined that adoption of the interim
surplus criteria would not adversely affect the bald eagle.
California Black Rail - California black rail (Laterallus jamaicensis coturniculus) have
recently been documented in the Virgin River Canyon, including the corridor above
Lake Mead (McKernan, 1999). In general, Flores and Eddleman (1995) found that
black rails utilize marsh habitats with high stem densities and overhead coverage that
were drier and closer to upland vegetation than randomly selected teriorMarsh edges
n sites.
he ICalifornia7bulrush and
with water less than 2.5 centimeters (1 inch) deep dominated by , 201
of t
ept. ber 29
three-square bulrush (Scirpus californicus and.S. americanus, respectively) are utilized
v D vem
most frequently. Areas dominated byation are also used regularly, but only in a small
cattail
No
N
v and hived on
proportion to their availability ajo generally within 50 meters (164 feet) of upland
c
in Na
vegetation wheretwater depth is , arcentimeters (1.2 inch). The occurrence and
i ed 6864 3.0
c
potential impacts to14-1 along the river corridor in Mexico are also discussed in
species
No.
Section 3.16.
Clark’s Grebe − Clark's grebes (Aechmophorus clarkii) are typically less abundant
than the western grebe at most locations throughout their range (Ratti, 1981; Zeiner et
al., 1990a). A 1977 winter survey found Clark's grebes comprised less than 12 percent
of Aechmophorus grebe sightings at locations within California and areas near Lake
Mead (Ratti, 1981). At Lake Mead, a total of 321 western grebes were detected during
the winter, while only three Clark's grebes were observed. At Lake Havasu, western
grebes are also more abundant than Clark’s grebes in the winter. However, Clark’s
grebes are more numerous in the breeding season, making up approximately 65 percent
of the breeding colony (Rosenberg et al., 1991). Although the cattail and bulrush marsh
habitat found at the Lake Mead delta exhibits characteristics preferred by Clark’s grebe,
it is not known whether this species currently occurs at the delta. The marsh habitat at
the Lake Mead and Virgin River deltas, and in the Colorado and Virgin rivers above
Lake Mead may potentially be utilized by Clark’s grebe and may be affected by the
interim surplus criteria.

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Cooper’s Hawk − Cooper’s hawks (Accipiter cooperii) are associated with deciduous
mixed forests and riparian woodlands and nests mainly in oak woodlands, but also use
willow or eucalyptus woodlands. The Cooper’s hawk nests near streams and prefers
mature trees with a well-developed understory for nesting sites (Ziener et al., 1990a).
Breeding activity has been documented in the lower Grand Canyon, below Separation
Canyon, and in the lower Virgin River above Lake Mead (McKernan, 1999). The
riparian habitat currently utilized by Cooper’s hawk in the lower Grand Canyon and
lower Virgin River may be affected by the interim surplus criteria.
Elf Owl − The elf owl (Micrathene whitneyi) is a secondary cavity nester and, as a
result, the population status of the elf owl is directly dependent on available nesting
holes in trees made by woodpeckers. As an insectivore, the elf owl is also dependent on
sufficient numbers of insects during the breeding season (Johnsgard, 1988). In
California, at the extreme northwest edge of its range, the elf owl is likely declining in
the few desert riparian habitats that it occupies (Johnsgard, 1988). There may also be a
general decline in Arizona, although it may be increasing its range in north-central
Arizona and western New Mexico. The species’ overall status in the Southwest has not
been determined. The elf owl was never a common or widespread species along the
lower Colorado River. Surveys of riparian habitats in the lower Colorado River Valley
in 1987 reported between 17 and 24 owls at ten different sites (CDFG,or
te i
I 25 r 1991).
heton breeding pairs
Population estimates in California for the early 1990s weret17
017
f
pt. oin the rGrand2
29, Canyon may
(CDFG, 1991; Rosenberg et al., 1991). Riparian habitat be
v. De vem
ion owl; however, based on the available
provide suitable breeding habitat for the elf
No
Nat
vajo hived on
information, it is unknown whether elf owls occur. The riparian habitat along the
c
n Na
Colorado RivercaboveiLake Meadar be utilized by elf owl and has the potential to be
ited 6864, may
affected by the interim -1
. 14 surplus criteria.

No

Gilded Flicker − The gilded flicker (Colaptes chrysoides) occurs along the lower
Colorado River Valley in southern Arizona and southeastern California (Rosenberg et
al., 1991). In California, the gilded flicker is an uncommon resident along the Colorado
River north of Blythe (Garrett and Dunn, 1981, CDFG, 1991). During the breeding
season, the gilded flicker is found in saguaro habitats, mature cottonwood-willow
riparian forests, and occasionally mesquite habitats with tall snags (CDFG, 1991;
Rosenberg et al., 1991). This species was historically widespread in riparian habitat all
along the Colorado River Valley. Based on available information, it is not known
whether this species occurs in the lower Grand Canyon, although suitable habitat is
present in both the riparian and mesquite habitats.
Southwestern Willow Flycatcher − The Southwestern willow flycatcher (Empidonax
traillii extimus) is a riparian obligate, neotropical migratory insectivore that breeds
along rivers, streams, and other wetlands where dense willow, cottonwood, tamarisk, or
other similarly structured riparian vegetation occurs (Service, 1995a; McKernan 1999;
AGFD, 1997e). Populations of breeding Southwestern willow flycatchers have been
recorded at the upper Lake Mead delta, the Virgin River delta, Mormon Mesa North,
and the Lower Grand Canyon (AGFD, 1997e; Sogge et al., 1997). However, due to

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high lake levels, as discussed previously, the Lake Mead and Virgin River delta willow
flycatcher habitat has been inundated. This change in reservoir elevation has permitted
suitable willow riparian habitat to develop in the Colorado River corridor from Lake
Mead up to approximately Separation Canyon (McKernan, 1999). The occurrence of
this species and habitat below Lake Mead to the SIB is discussed in the BA for this
proposed action (Reclamation, 2000).
The Grand Canyon population of Southwestern willow flycatcher is important from a
scientific and management perspective because it is one of the longest continuously
monitored populations in the southwest (Sogge et al., 1997). In support of this view,
the USFWS designated river mile 39 downstream to river mile 71.5 as critical habitat
for this species (USFWS, 1997a, 1997c). This habitat occurs in the upper Grand
Canyon and will not be affected by the interim surplus criteria.
High lake levels (above 1192 feet) appear to be detrimental to Southwestern willow
flycatcher nesting habitat at Lake Mead delta due to potential loss of suitable nest trees
(Reclamation, March 1998). Lake levels below 1192 feet during the willow flycatcher
breeding season (April through August) appear to allow for increased willow habitat
establishment which would be beneficial to the species. From January 1978 until June
1990, Lake Mead elevations were above 1182 feet on a continuous erior In June 1990,
basis.
Int below that
Lake Mead elevation declined to approximately 1182 feet and stayed 017
f the
p . o er 29, 2
elevation until the end of 1992 (Reclamation, 2000). tIf saturated soils are present in
. De
b
areas occupied by willow flycatcher, declines in lake levels during June have little to no
ion v Novem
at
jo N v Mead’s
effect on nesting. In contrast, when Lake ed on elevation is high enough to inundate
Nava duringiJune and July (Reclamation, 2000), willow
in
the delta, which typically occurs, arch
64
cited be affected because their territories and possibly nest sites would
flycatchers would not4-168
o. 1
be established.NBecause suitable habitat utilized by Southwestern willow flycatcher
may be affected by changes in Lake Mead water levels that would result from
implementation of the interim surplus criteria, the species is considered in the
environmental consequences section below. The interim surplus criteria are not
expected to result in hydrologic changes below Hoover, Davis and Parker dams that
would adversely affect the flycatcher.
Yuma Clapper Rail − The Yuma clapper rail (Rallus longirostris yumanensis), one of
seven North American subspecies of clapper rails, occurs primarily in the lower
Colorado River Valley in California, Arizona and Mexico. It is a fairly common
summer resident from Topock Gorge south to Yuma in the United States, and at the
Colorado River delta in Mexico. In the area under consideration, the Yuma clapper rail
is associated with freshwater marshes with the highest densities of the subspecies
occurring in mature stands of cattails and bulrush (Reclamation, August 1999). In
recent years, individual clapper rails have been heard at Laughlin Bay and Las Vegas
Wash in southern Nevada (NDOW, 1998), and individuals have been documented at the
Virgin and Muddy rivers including the Virgin River floodplain between Littlefield, AZ
and the Virgin River Delta, NV (McKernan, 1999), and at sites within the lower Grand
Canyon (McKernan, 1999). The occurrence of the Yuma Clapper below Lake Mead to

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the SIB is discussed the BA for this proposed action (Reclamation, 2000). The marsh
habitat utilized by Yuma clapper rail has the potential to be affected by the interim
surplus criteria.
Western Yellow-billed Cuckoo − Historically, the western form of the yellow-billed
cuckoo (Coccyzus americanus) was a fairly common breeding species throughout the
river bottoms of the western United States and southern British Columbia (Gaines and
Laymon, 1984). Due to the loss of riparian woodland habitat, the cuckoo has become
an uncommon to rare summer resident in scattered locations throughout its former
range. Western yellow-billed cuckoo have been documented in riparian habitat in the
lower Grand Canyon and Virgin River above Lake Mead (McKernan, 1999)
(Reclamation, 2000) as well as in habitat along the river corridor below Lake Mead and
has the potential to be affected by the interim surplus criteria.
3.8.3.4

SPECIAL-STATUS FISH SPECIES

Described below are special-status fish species present within the area under
consideration. Table 3.8-3 lists special-status fish species including common name,
scientific name and status. Currently, the Service is supplementing existing recovery
plans for the four endangered fish species included in this analysis. erior
t

7
he In
. of t listed9, 201
Critical habitat has been designated for each of the federally er 2 fish species (Federal
pt
De
Register: March 21, 1994), and portionsionthis habitat existb
of v.
em within the area of potential
Nat d on Nov
effect (Reclamation, 2000). vajo
ive
Na
d in 64, archTable 3.8-3
cite
68
Special-Status -1 Species Potentially Occurring Within the Area of Analysis
. 14 Fish
No
Common Name

Scientific Name

Bonytail

Gila elegans

Colorado
pikeminnow

Ptychocheilus
lucius

Flannelmouth
sucker

Catostomus
latipinnis

Humpback chub
Razorback sucker

Gila cypha
Xyrauchen texanus

Status
Federally Listed Endangered (critical habitat designated);
California Endangered;
Nevada State Protected
Federally Listed Endangered (critical habitat designated);
California Endangered
Federal Species of Concern;
Arizona Wildlife Species of Concern;
Bureau of Land Management Nevada Special Status
Species
Federally Listed Endangered (critical habitat designated)
Federally Listed Endangered (critical habitat designated)

Bonytail − Adult bonytail (Gila elegans) were once found throughout the big rivers
and major tributaries of the Colorado River basin. Younger fish utilize the smaller
streams and quiet areas. Bonytail prefer substrate which consists of clay, soft mud, or
mud and sand, or occasionally rocks, gravel or rubble with little or no vegetation (Sigler

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and Miller, 1963; Wydoski, 1995). Adults range between eight and 17 inches in length
and weigh just over one pound. The species can live for over 40 years. Spawning
occurs in late spring to early summer usually over gravel bars with no nest being
constructed. Gravid females can carryover 10,000 eggs each. Bonytail are carnivorous,
feeding on insects, crustaceans, small fish, and snails; however, filamentous algae are
often consumed (NPS, 1998).
The bonytail is now the rarest native fish within the Colorado River Basin (NPS, 1998).
The decline in the number of bonytail are thought to be a result of changes in historical
stream flow and water temperatures, blockage of migratory routes by dams and
introduction of non-native fish species. At Lake Powell, present numbers are accounted
for by fish older than 40 years of age; no recruitment has been demonstrated in recent
years (NPS, 1998).
Bonytail are believed to be extirpated in the Colorado River from Glen Canyon Dam to
Hoover Dam (McCall, 1979 and Reclamation, 1996a). Small populations may still
exist in the Upper Basin, but there is much confusion in fish identification due to the
similarity in physical appearance with roundtail chubs (Reclamation, 1996a). Five
suspected bonytail were captured in Cataract Canyon between 1985 and 1988, with one
caught in Lake Powell near Wahweap Marina (Maddux et al., 1993erior
and Reclamation,
Int
1995).
017
f the

9, 2
pt. o
. De efromeHoover Dam to Davis
b r2
Critical habitat for bonytail includes theion v
t Colorado River m
Naincludes n Nov
Dam, including Lake Mohave.aIt also ed o the Colorado River from the northern
v jo
boundary of Havasu National Wildlife Refuge to Parker Dam, including Lake Havasu.
in Na 4, archiv
cited 1686
The largest remaining population of bonytail in the entire Colorado River Basin resides
4in Lake Mohave. . 1 were at least nine augmentation stockings of bonytail into Lake
No There
Mohave between 1981 and 1991 (Reclamation, 1996a). Efforts are being undertaken to
repatriate bonytail back to Lake Havasu from lakeside coves using young obtained from
Dexter National Fish Hatchery (Reclamation, 1996a). The primary limiting factor for
bonytail appears to be non-native fish predation of the early life stages (egg to subadult)
(Reclamation, 1996a).
Colorado pikeminnow − The Colorado pikeminnow (Ptychocheilus lucius) is the
largest member of the minnow family within North America and is endemic to the
Colorado River system. It was, historically, the top predator fish in the Colorado River,
but native populations are now restricted to the upper Colorado River Basin
(Reclamation, 1996a). A portion of their current distribution includes the Colorado
River from Palisades, Colorado, downstream to Lake Powell (NPS, 1998). Colorado
pikeminnow have been captured in Lake Powell as recently as 1999 (Reclamation, file
data). Designated critical habitat within the area of effect for the analysis is limited to
the normal pool elevation of Lake Powell. Colorado pikeminnow are now considered
extirpated from the entire Lower Basin; where they were once extremely abundant. The
last known wild adults from the lower Colorado River were captured in the 1960s, and
the last known specimens from the Gila River basin were collected in 1958 (Minckley,

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1973). Colorado pikeminnow were taken from Lake Havasu in the 1970s. Populations
in the upper basin are thought to be stable or increasing, with documented natural
recruitment.
The species is adapted to large seasonal flow variations, high concentrations of silt,
turbulence, periodically low food availability and naturally variable riverine
subsystems. It is typically a big river fish where the current is strong and the water
heavily silt laden. Colorado pikeminnow are migratory and can utilize anywhere from
100 to 200 miles of river to complete their life cycle. Spawning takes place from spring
to late summer depending on water temperatures. Larva and juvenile pikeminnow can
drift 60 to 150 miles from spawning beds into nursery areas where they mature to a size
that mostly prevents predation (Maddux et al., 1993; Sigler and Miller, 1963).
Flannelmouth sucker − The flannelmouth sucker (Catostomus latipinnis) was
historically found in medium to large rivers throughout the upper and lower Colorado
River drainage (Joseph et al., 1977; AGFD, 1996a). Although the flannelmouth sucker
is currently widely distributed in the upper Colorado River Basin (Holden and Stalnaker
1975a, b; McAda, et al., 1994), its occurrence in the lower Colorado River Basin has
become more restricted. The species’ range in the Upper Basin includes the main stem
of the Colorado River, numerous tributaries that drain a large portionrof r
te io Colorado and
Utah, and the San Juan River drainage in New Mexico and tUtah.nIn the Lower Basin,
he I
017
of
pt. of suitable 9, 2 (Sublette et
2habitat
the flannelmouth sucker occurs only in localized areas
. De
ber
al., 1990). Populations in the Lower Basin occur in ovem Colorado River, Virgin
ion v N the Little
Nat d Canyon, and immediately below Davis
River, Colorado River in Glen ajo
v Canyon, iGrandon
ve
Na
Dam, and severalted intributariesarch Colorado River above Lake Mead (AGFD,
small
, to the
ci
864
1996a; Valdez and Carothers, 1998).
4-16
1

No.

Flannelmouth suckers typically require medium to large flowing streams and react
poorly to impounded habitats or habitats influenced by impoundments (Minckley,
1973), and the artificial thermal regime created by impoundments. Subadult
flannelmouth suckers in the Grand Canyon use sheltered shoreline habitats, backwaters,
and tributary inflows (Valdez and Ryel, 1995). Conversely, adults can be found in a
variety of mainstem habitats, including: tributary mouths, vegetated shorelines, midchannel cobble bars (Valdez and Ryel, 1995), eddies (Holden and Stalnaker, 1975a; and
Valdez and Ryel, 1995) and riffles (Holden and Stalnaker, 1975a). Spawning can take
place from spring to early summer and is often preceded by an upstream migration.
Since 1986, the AGFD has conducted yearly monitoring of flannelmouth sucker
populations in the Colorado River from Lees Ferry downstream to Lake Mead. The
Glen Canyon Monitoring and Research Center (1998) has funded monitoring and
research activities for this species. The objective of this program is to provide the
knowledge base required to implement ecosystem management strategies within an
adaptive management framework.

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Humpback chub − Endemic to the Colorado River, the humpback chub (Gila cypha)
inhabits the canyon-bound sections of the Colorado, Green and Yampa rivers, with high
fidelity for particular localized sites. Young are not known to widely disperse. The
historical abundance and distribution of the fish is not well known. Designated critical
habitat includes the Colorado River from Nautiloid Canyon to Granite Park in the
Grand Canyon, and the lower eight miles of the Little Colorado River, including its
confluence with the Colorado River. The largest population still extant is found in and
near the Little Colorado River within the Grand Canyon (Maddux et al., 1993; Valdez
and Ryel, 1995). This population uses the Little Colorado River for spawning and
rearing. The possibility exists that humpback chub found in the Middle Granite Gorge
and lower Grand Canyon may represent a separate population (Reclamation, 1996a).
Humpback chub becomes reproductively active between May and July depending on
location and the hydrograph. Males become reproductively mature within three years.
Spawning occurs during the highest spring flows when water temperatures approach
68°F (20°C) over cobble or gravel surfaces. Larvae tend to utilize silty bottom habitats.
Later, humpback chub utilize a variety of habitats within a boulder strewn canyon
environment (i.e., pools, riffles and eddies). They move between habitats dependent on
life history needs and natural habitat change (NPS, 1998).

r
terio
Ininvertebrates and
Young humpback chub feed mainly from the bottom eatingthe
of small , 2017
pt.also feed 29floating aquatic and
diatoms. Adults also feed mainly from the bottom but
. De e ber on
terrestrial insects (SWCA, 1997; Valdezion v
and Ryel, 1995;m
at
Nov Wydoski, 1995).
ajo N ived on
av
Razorback sucker d The razorback ch
− in N 4, ar sucker (Xyrauchen texanus) was formerly the most
cite 1 of 6
widespread and abundant 68the big-river fishes in the Colorado River. In the lower
14basin, razorbacko.
N sucker apparently began to decline shortly after impoundment of Lake
Mead in 1935. Today the species occupies only a small portion of its historical range,
and most occupied areas have very low numbers of fish. Critical habitat for the
razorback sucker includes Lake Mead and Lake Mohave, and the river reach between
them. It also includes the Colorado River and its 100-year floodplain from Parker Dam
to Imperial Dam. Reclamation's BA includes a detailed discussion of this species
occurrence and requirements (Reclamation, 2000).
In Lake Mead, the fish were abundant for many years after the reservoir filled, but
declined during the 1960s and 1970s. The current population in Lake Mead is
estimated to be less than 300 fish. The capture of a small number of juvenile adults
since 1997 along with recent capture of larval razorback sucker in the spring of 2000
(Holden, Personal communication) indicates some successful recruitment is taking
place. There are two populations of razorback sucker in Lake Mead in Las Vegas Bay
and Echo Bay. A five-year study is underway to determine population size and
movements of this fish and to determine why there is a small number of fish able to
recruit, thus enabling a small number of razorback sucker to persist in Lake Mead.

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The razorback sucker is a large fish, reaching over two feet in length and eight pounds
in weight. Reproduction in the lower basin has been studied in Lake Mead and Lake
Mohave. Spawning in Lake Mohave typically begins in January or February, while in
Lake Mead it begins slightly later (Jonez and Sumner, 1954). Spawning typically runs
30 to 90 days at water temperatures ranging from 55°F to 70°F (13°C to 21°C).
Spawning areas tend to be wave-washed, gravelly shorelines and shoals. Fish spawn in
water from three to 20 feet in depth with the majority of fish in the five- to 10-foot
range. Razorback suckers apparently spawn continuously throughout the spawning
season, with females releasing only a portion of their gametes at each event. Spawning
occurs both day and night on Lake Mohave (Reclamation, file data). Eggs hatch in five
to 10 days depending on water temperature. Optimal hatching success is around 68°F
(20°C); hatching does not occur at extremes of cold or hot (50°F or 86°F; 10 C to 30 C)
(Marsh and Minckley, 1985). Larvae swim up within several days and begin feeding on
plankton. Juvenile razorback suckers in lakeside rearing ponds hide during the day in
dense aquatic vegetation and under brush and debris and in rock cavities (Reclamation,
1996a, 2000).
Most of the remnant populations of razorback sucker are found in Lake Mead and Lake
Mohave (Reclamation, 2000). They are considered rare in the Grand Canyon and have
o data).
been documented in Lake Powell as recently as 1999 (Reclamation, file r
nteri by non-native
Spawning success has been limited by the predation of eggshe Iyoung017
and
of t
,2
ept. ber 2sucker that have been
species. Currently, efforts are being made to introduce razorback 9
.D
v
raised in areas free of predators into Lake n
to vem
NatioMohaveNohelp establish a larger population
n
of breeding adults, and continued studyiofed o
the persistent population in Lake Mead is
vajo
in Na 4, arch v
planned (Reclamation, 2000).
d
ite
6

c
168
. 143.8.4 ENVIRONMENTAL CONSEQUENCES
No

This section evaluates the potential effects on special-status species and their habitat
that could occur as a result of implementation of the interim surplus criteria alternatives
under consideration. This section is divided into three main special-status species
categories: plants, wildlife and fish. For each category, the potential effects under
baseline conditions are presented first, followed by a discussion of the alternatives as
compared to baseline conditions.
3.8.4.1

EFFECTS ON SPECIAL-STATUS PLANT SPECIES

Only four plant species would potentially be affected by hydrological changes
associated with the interim surplus criteria alternatives: Geyer’s milkvetch, Grand
Canyon evening primrose, Las Vegas bear poppy and sticky buckwheat.
3.8.4.1.1

Baseline Conditions

Geyer’s milkvetch, which occurs along the shoreline of Lake Mead, is mainly
threatened by loss of habitat from inundation as a result of rising water levels at Lake

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Mead, invasion of shoreline (beach) habitat by tamarisk and arrowweed, and possibly
trampling and grazing by burros. Shoreline recreation does not currently appear to be a
major threat to this species because the beaches where it occurs do not receive heavy
recreational use. This species would be affected by variations in Lake Mead surface
elevations if suitable habitat were inundated. Baseline conditions indicate a decreased
potential over time for such inundation to occur. If lake levels decline, exposing sand
dune habitat and sandy soils, the species could benefit. However, if these areas are
colonized by tamarisk after being exposed, there would be no net benefit.
Grand Canyon evening primrose are found in beach habitat within the Grand Canyon.
The beach habitat in the Grand Canyon is often invaded by riparian vegetation and is
also utilized by recreationists, which results in adverse conditions for Grand Canyon
evening primrose establishment. To the extent that beach habitat is altered by releases
from Glen Canyon Dam, this species is covered under the Glen Canyon Dam ROD
(1996) and Adaptive Management Program. Indirect effects to the habitat for this
species may, however, result from fluctuations in Lake Mead pool elevations. Under
baseline conditions, Lake Mead elevations are projected to decline over time.
Reductions in Lake Mead elevations would likely result in an increase in exposed beach
habitat in the lower Grand Canyon to Lake Mead that would potentially provide more
r
suitable habitat for Grand Canyon evening primrose.
terio

7
he In
of Lake Mead shoreline. As
. the t r 29, 201
pt
Las Vegas bear poppy occurs along the lower levels of
. De embe
with the Geyer’s milkvetch, this speciesion v benefit from lower water levels at Lake
would
at
Nov
Mead and would be adversely ajo N byed on
affected v any increases in water levels. Benefits of
i
Nav
lower surface elevations would bearch if invasion of exposed areas by tamarisk or
d in 64, negated
ite
c
other weedy exotic plant species were to occur.
168
. 14No
Sticky buckwheat is found primarily along the Overton Arm of Lake Mead with
smaller, potentially significant populations occurring in the vicinity of Overton Beach,
along the Virgin River Valley, and along the Muddy River. As with the other three
special-status plant species discussed, the major threats to sticky buckwheat at Lake
Mead are the loss of habitat from inundation as the result of rising water levels at Lake
Mead, and the invasion of shoreline (beach) habitat by tamarisk and arrowweed. This
species could potentially benefit from lower lake levels at Lake Mead provided the
newly exposed habitat was not colonized by weedy exotic plant species.
3.8.4.1.2

Effects of the Alternatives

Potential effects to special-status plant species under the each of the alternatives would
be similar to baseline conditions. Each alternative would result in Lake Mead
elevations that would vary from those under baseline conditions, with the Flood Control
Alternative resulting in slightly higher reservoir elevations, and the Basin States, Six
States, California and Shortage Protection alternatives having lower reservoir elevations
as compared to baseline projections. (Section 3.3 discusses the modeling results
concerning potential future reservoir elevation trends in detail.) The differences in

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potential future Lake Mead elevations under the alternatives as compared with baseline
conditions are not expected to adversely affect the special-status plant species discussed
above, as lower Lake Mead elevation trends may benefit these species.
3.8.4.2

EFFECTS ON SPECIAL-STATUS WILDLIFE SPECIES

Special-status wildlife species with potential to occur in the area under consideration are
Arizona Bell’s vireo, bald eagle, California black rail, Clark’s grebe, Cooper’s hawk, elf
owl, gilded flicker, Southwestern willow flycatcher, Yuma clapper rail and western
yellow-billed cuckoo.
Under baseline conditions and each of the alternatives, the water surface elevation
projected for Lake Powell indicates a potential for slightly declining water levels during
the first 15 years of the period of analysis. Figure 3.3-6 in Section 3.3 shows modeled
Lake Powell elevations. The differences between the alternatives and baseline
conditions would not affect any special-status wildlife species identified for this
analysis and as a result, Lake Powell is not discussed further.
3.8.4.2.1

Baseline Conditions

ior

Water fluctuations of Lake Mead generally preclude development ter
7
he In of shoreline riparian
vegetation, with the exception of tributary inflow areas such as the9, 201River and
. of t r 2 Virgin
pt
. e e vegetation
be
Lake Mead deltas (Reclamation, 1999). WoodyD
ion v riparian m to the(i.e., cottonwood
at Separationv
No Canyon
and willow) become abundant fromN
Lake Mead delta
ajo below d on
as lake levels declinedin Nav highhive years of 1983-1986 (Reclamation, 1995).
following rc runoff
a
d
cit for 16864,
As the probabilitye declining reservoir levels increases over time under baseline
projections (asNo. 14 Figure 3.3-13 in Section 3.3), an increase in the amount of
shown on
sediment exposed in the Lake Mead and Virgin River deltas would again create
favorable conditions for establishment of woody riparian habitat. An increase in
riparian habitat along the deltas would potentially benefit Arizona Bell’s vireo,
Cooper’s hawk, elf owl, gilded flicker, western yellow-billed cuckoo and Southwestern
willow flycatcher. The interim surplus criteria alternatives are not expected to impact
these species in the river corridor below Hoover Dam to the SIB (Reclamation, 2000).
The increase in the probability for Lake Mead water levels to decline under baseline
projections would also increase potential for sediment exposure that may create suitable
conditions for marsh vegetation to develop and/or expand at the Lake Mead and Virgin
River deltas, as well as along the Colorado, Virgin and Muddy rivers above Lake Mead.
This would in turn increase the amount of preferred habitat for California black rail,
Clark’s grebe and Yuma clapper rail.
Riparian and marsh vegetation is typically located within the shallow water table zone
near the lake shoreline. Although lowering lake levels has the potential to increase the
amount of riparian and marsh vegetation because of increased sediment exposure, these
habitat types would only become established if lake levels do not drop excessively. If

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the exposed sediment is too far above the water table, riparian and marsh habitat is not
likely to become established.
3.8.4.2.2

Effects of the Alternatives

Potential effects on special-status wildlife species would be similar to baseline
conditions. Each alternative would result in Lake Mead elevations that would vary
from those under baseline conditions, with the Flood Control Alternative resulting in
slightly higher reservoir elevations, and the Basin States, Six States, California, and
Shortage Protection alternatives having lower reservoir elevations as compared to
baseline projections. (Section 3.3 discusses the modeling results concerning potential
future reservoir elevation trends in detail.) Under each of the alternatives, vegetation
associated with Lake Mead, including riparian and marsh habitat in the Virgin River
and Lake Mead deltas, would experience changes similar to those described above
under baseline conditions. Consequently, the potential for changes in special-status
species’ habitat associated with Lake Mead, and the Lake Mead and Virgin River deltas
under the alternatives would be similar to those described for baseline conditions above.
3.8.4.3

EFFECTS ON SPECIAL-STATUS FISH SPECIES

rior

Operations at Glen Canyon Dam and Hoover Dam include variouste
e In programs designed
1
of th 29, 2 the7
to aid in the conservation and recovery of endangered .native species in 0 lower
ept
r
Colorado River basin. These programs ion v. D
include Sectionembe
v 7 consultations under the ESA,
atand ROD (1996), and the LCRMSCP.
n No
the Glen Canyon Dam Operationo N
AMP
vaj the ived o
Reclamation is also d participant in rchUpper Colorado and San Juan River Basin
a in Na
,a
cite 1 Programs for endangered fish in the upper Colorado River
Recovery Implementation6864
basin. CriticalNo. 14for all four of the endangered fish species has been designated by
habitat
the Service. Adverse modification of these habitats is prohibited under Section 7 of the
ESA. These programs and protections will remain in effect under baseline conditions
and each of the interim surplus criteria alternatives. As discussed, conditions are not
favorable for endangered fish. Future baseline conditions and each of the interim
surplus criteria are expected to increase, to varying degrees, the potential for reduced
reservoir surface elevations. The following discuss effects of the alternatives on each of
the special-status fish species.

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3.8.4.3.1

CHAPTER 3

Baseline Conditions

Bonytail - Under baseline conditions, it is anticipated that bonytail in the Colorado
River Basin and their designated critical habitat would continue to be protected under
the ESA. Reclamation has consulted with the Service under Section 7 of the ESA on
the operation of Glen Canyon and Hoover dams. The resulting biological opinions will
remain in effect. Reservoir operations remain within historical ranges, and efforts to
protect, recover, and monitor the species status would continue.
The main effort to protect and conserve bonytail in the Lower Basin is the
reintroduction of fingerling bonytail from the Dexter National Fish Hatchery, New
Mexico that have been reared in predator-free ponds into Lake Mohave by the NFWG.
The primary limiting factor for bonytail under existing habitat conditions is predation of
early life stages by non-native species. This program is designed to address predation
and maintain genetic stocks of bonytail. The main efforts to protect and conserve
bonytail in the Upper Basin are conducted through the Upper Colorado Recovery
Implementation Program (UC-RIP). This program is designed to recover the bonytail
in the Upper Basin by 2010.
Colorado pikeminnow - Under baseline conditions, it is anticipated rior Colorado
e that pikeminnow
pikeminnow would continue to be restricted to the Upper Basin.Int
Colorado7
f the 9, 201
and their designated critical habitat would continue pt.be protected under the ESA. The
to o
r2
De
mbe
Colorado pikeminnow is extirpated fromon areas considered in this analysis except for
all v.
ove
ati
Lake Powell. The ability of the jColorado ed on N to successfully reproduce in
a o N iv pikeminnow
av
Lake Powell has not beenN
arc Successful spawning occurs in riverine habitats
d in confirmed. h
cite and16864, drift downstream to rear in sheltered environments.
above Lake Powell, - larvae then
14
Survival of larvae .that drift into Lake Powell is limited by predation by non-native fish.
No
As development of water continues to occur in the upper basin, lower lake elevations
are expected to occur. This will increase the amount of sheltered riverine habitat and
indirectly benefit the survival of some larvae by preventing them from drifting into
open water areas of the reservoir where the risk of predation is greater. The main
efforts to protect and conserve Colorado pikeminnow in the Upper Basin are conducted
through the UC-RIP, plus the San Juan River Basin Recovery Implementation Program
(SJ-RIP). This program is designed to recover the pikeminnow in the Upper Basin by
2010.
Flannelmouth sucker - Under baseline conditions, it is anticipated that flannelmouth
sucker populations in the project area would continue to be found in riverine habitats
and tributaries. The species is not well adapted to reservoir habitats and are seldom
found there. The low survival of eggs and larvae in the reservoirs may be attributed to
impacts from cold water temperatures or predation by non-native species. These
conditions would continue to limit the reproductive success of flannelmouth sucker in
the reservoirs. For flannelmouth sucker that spawn in rivers upstream of Lake Mead
and Lake Powell or other inflow areas, survival of larvae that drift into the reservoirs is
limited by cold water temperatures and predation of non-native fish. Lower lake

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elevations may increase the amount of sheltered riverine habitat and indirectly benefit
the survival of some larvae by preventing them from drifting into open water areas of
the reservoir where the risk of predation is greater. Efforts to improve habitat
conditions under the UC-RIP, SJ-RIP, Glen Canyon Dam AMP and the Lower
Colorado MSCP will benefit the flannelmouth sucker.
Humpback chub - Under baseline conditions, it is anticipated that humpback chub
populations would continue to be restricted to riverine and tributary habitats in the
Colorado River in the Grand Canyon. The humpback chub and its designated critical
habitat would continue to be protected under the ESA, the 1996 ROD, flow regimes and
other activities as prescribed under the 1995 biological opinion and the Glen Canyon
Dam AMP. In addition to the populations of the Grand Canyon, there are five stable
populations in the Upper Basin. The UC-RIP and SJ-RIP are making progress toward
recovery of the species. The humpback chub is considered extirpated from all other
areas within the lower Colorado River Basin.
Razorback sucker - Under baseline conditions, it is anticipated that razorback sucker
populations in the Lower Basin would continue to be limited primarily to Lake Mead
and Lake Mohave and designated critical habitat would continue to be protected under
the ESA. Spawning success has been limited by predation of eggstandor
n eri larvae by nonnative fish. Efforts are currently being made by the NFWG hesupplement7
to I
201 adult
of t
pt. lakes er 29, river with young
breeding populations of razorback suckers by stocking
. De
band the
io at v Mohave
reared in predator free ponds. Operations n Lake Novemare conducted in an effort to
Nat
conserve and protect razorback sucker by ed on
vajo hiv controlling the amount of lake fluctuation
in Na
rc
during the spawning season. 64five-year study of the remnant razorback sucker
ited 68 A , a
c Mead is scheduled to be completed by 2002. These practices are
population in Lake 14-1
No.
expected to continue under baseline conditions and all the interim surplus criteria
alternatives.
3.8.4.3.2

Effects of the Alternatives

Potential effects on the five special-status fish species discussed above would be similar
to baseline conditions. Each alternative would result in Lake Powell and Lake Mead
surface elevations that would vary from those under baseline conditions, with the Flood
Control Alternative resulting in slightly higher reservoir elevations, and the Basin
States, Six States, California and Shortage Protection alternatives having lower
reservoir elevations as compared to baseline projections. (Section 3.3 discusses the
modeling results concerning potential future reservoir elevation trends in detail.)
Efforts toward protection and recovery of these species would continue under each of
the alternatives in the same manner as describe above for baseline conditions. Potential
changes in BHBF and low steady summer flow frequencies are discussed in Section 3.6
of this FEIS, and Reclamation has determined that these effects would not be likely to
adversely affect special-status fish species.

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3.9 RECREATION
3.9.1

INTRODUCTION

The Colorado River, Lake Mead and Lake Powell provide water-based recreation
opportunities that are of local, regional and national significance, as well as
international interest.
This recreation analysis addresses five specific recreation-related issues associated with
potential effects that could result from implementation of the interim surplus criteria
alternatives considered in this document. The issues addressed are potential effects to:
•

Reservoir marinas and boat launching and shoreline access for Lake Powell
and Lake Mead;

•

Lake Mead and Lake Powell boating and navigation;

•

River and whitewater boating;

•

Sport fishing in Lake Powell, Lake Mead and the Colorado or
i River below
Inter 17
Hoover Dam; and
he

20
of t
ept. ber 29,
• Recreational facilities operationalv. D
n costs. em
Natio d on Nov
vajo
e
The interim surplus alternatives would not change the current and projected operations
in Na 4, archiv
d Havasu and thus would not affect recreation on those reservoirs.
of Lakes Mohavete
ci and 1686
14No. MARINAS, BOAT LAUNCHING AND SHORELINE
3.9.2 RESERVOIR
ACCESS
This section considers potential effects of the interim surplus criteria alternatives on
Lake Powell and Lake Mead marinas, boat launching facilities and other important
shoreline access areas.
3.9.2.1 METHODOLOGY
Information in this section was compiled after review of available published and
unpublished sources, and through personal communication with Reclamation, NPS and
resource specialists. Thorough review of existing literature on the Colorado River
provided information on reservoir recreation use for both Lake Powell and Lake Mead.
Where available, the number of facilities at each marina, boat launching ramp and
shoreline access area are included.
From the information compiled, representative threshold pool elevations were selected
for facilities, at or below which certain facilities may be rendered inoperable or
relocation of facilities could be required to maintain their operation. These thresholds

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were chosen based on either information provided in studies, communications with NPS
personnel, or from comments received regarding the DEIS. Discussions of the
probabilities of these thresholds occurring is detailed in the Environmental
Consequences Section (Section 3.9.2.3). The probability of reservoir elevations
occurring below these levels under baseline conditions and the action alternatives was
identified using river system modeling as described in Section 3.3.
Data generated from the river system model include the probability (represented
graphically in the Environmental Consequences section) that the water level related to
each alternative would be above the specified “threshold” pool elevations for each year
during the period of analysis. The graphs indicate the general trend of elevation
probabilities and present the incremental differences in probabilities for baseline
conditions and each of the alternatives.
3.9.2.2 AFFECTED ENVIRONMENT
Recreational boating on Lake Mead and Lake Powell is dependent upon access to the
water via shoreline facilities such as marinas, docks and launch ramps. Fluctuation in
water levels is a normal aspect of reservoir operations, and facilities are designed and
operated to accommodate it. However, decreased pool elevations or rior
e increased
variations or rates in pool elevation fluctuation could resultthe Int
in increased operation costs,
017
f
temporary closures or possibly permanent closures. pt. o
29, 2
e
r

D
be
n v.
ovem
atioand on NMead depend on annual inflow from
Reservoir pool elevations at Lake Powell d Lake
ajo N
Navandarchivefrom the respective dam to the Colorado
the Colorado River d in
upstream,
outflow
cit for 16864,
River downstreame water deliveries. Operation of the Colorado River generally
14results in the highest pool elevations in Lake Powell in mid-summer and in Lake Mead,
No.

early winter. In general, pool levels in Lake Powell and Lake Mead tend to fluctuate on
an annual cycle rather than on a monthly or seasonal cycle. Lake Powell historical pool
fluctuations have normally ranged from 20 to 25 feet per year (Combrinks and Collins,
1992). Since operation of Glen Canyon Dam began in 1966, Lake Mead pool
fluctuation has normally ranged from 5 to 25 feet per year.
3.9.2.2.1 Lake Powell Recreation Resources
Lake Powell is located in the Glen Canyon National Recreation Area (GCNRA) in
southern Utah and northern Arizona. Typical recreation activities that occur at Lake
Powell include swimming and sunbathing, power boating, fishing, off-beach activities
associated with boat trips (such as hiking and exploring ruins), house boating, personal
water craft use, canoeing, kayaking, sailing, and other activities (USBR, 1995b). A
carrying capacity study (NPS, 1991) provided information on the potential limits of
boater use on Lake Powell. The study also showed that the average length of stay at the
GCNRA is 4.5 days.

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Visitation numbers for the entire GCNRA between 1990 and 1999 are provided in
Table 3.9-1. The data indicate that there are seasonal variability in recreation use. The
majority of use occurs in the summer months of June, July and August. The visitation
numbers shown for 1995 through 1999 are considerably lower than visitation between
1990 and 1994 due to changes in NPS methods for calculating visitation. However, the
seasonal pattern of visitation does not change; use remains highest in summer months.
The majority of visitors to the GCNRA travel either less than 30 miles to visit (29.1
percent) or travel 121 to 240 miles (28.9 percent). This indicates that the area is used
predominantly by local and regional visitors.
Table 3.9-1
Glen Canyon National Recreation Area Visitation
Year

Jan

Feb

March

April

May

June

July

August

Sept

Oct

Nov

Dec

Total

1990

77,617 109,042 135,039 253,638 289,993 501,288 467,981 483,023 350,026 227,061 129,691

78,750 3,103,129

1991

81,875

97,120 118,182 199,462 346,764 451,674 503,752 568,030 396,785 247,982 120,822

78,442 3,210,890

1992

83,044 114,889 139,787 246,993 346,727 525,610 572,869 659,809 478,032 245,565 122,386

82,847 3,620,558

1993

60,927

1994

69,663 120,307 174,272 264,265 364,826 576,355 665,583 439,177 321,961 212,729

83,903 123,836 201,141 372,425 526,202 624,549 644,534 530,550 259,119 111,607
99,097

76,031 3,470,194
63,607 3,371,842

94,508 50,362 2,469,521
ior
te89,670 48,269 2,532,087
1996
In r 17
0
f the
1997 49,954 54,401 115,523 157,249 245,000 288,742 420,927 437,846. 266,992 187,467 , 85,595 48,507 2,458,203
pt o er 29 2
e 285,105 197,673 77,247 50,315 2,467,199
1998 39,241 55,538 89,971 171,234 267,509 389,167 445,423 398,776
v. D
mb
ation on441,791ve
No 305,006 200,457 89,799 55,503 2,667,249
1999 44,755 51,657 118,141 155,831 261,931N
jo 426,744 515,641
Nava archived
Source: Based on NPS data.
in
4,
cited 16 numbers changed in 1995. This resulted in significant reductions in visitation numbers
* NPS methods for calculating visitation86
compared to prior years. 14No.
*

35,814

66,553

88,414 151,369 196,905 410,610 435,840 461,431 285,118 192,597

41,303

1995

50,553

96,296 209,243 231,655 419,288 447,417 442,180 268,266 187,949

Recreation boating is the largest type of boating activity on Lake Powell, with an
estimated 1.5 million boater nights per year in 1988. Although use at some of the major
marinas, such as Wahweap, Hall’s Crossing and Bullfrog, decreased during a low water
period in 1989, the total number of boats on Lake Powell was reported to have
increased 14.5 percent by July 31, 1989, compared to the same period in 1988 (USBR,
1995b). Specific facilities and reservoir elevations important to their operation are
discussed in the following sections. Map 3.9-1 depicts Lake Powell and the locations of
shoreline facilities.

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Map 3.9-1
Lake Powell and Associated Shoreline Recreation Facilities

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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3.9.2.2.2 Shoreline Public Use Facilities
Public use facilities at Lake Powell that include water-based recreation activities are
Wahweap, Dangling Rope Marina, Halls Crossing, Bullfrog, Hite, and Antelope Point.
The GCNRA Proposed General Management Plan (NPS, 1979) describes the estimated
capacity and development at these areas; these estimates are based on general concepts
only and further detailed planning was proposed to begin after the plan’s acceptance in
1979. Table 3.9-2 summarizes the activities at each of the sites. If the actual number of
improvements (boat slips, mooring buoys, houseboats, etc.) at a facility are known, it is
listed in Table 3.9-2; otherwise, the presence of an improvement is indicated with a
bullet (•). If an improvement does not exist, it is denoted with “N/A.” Below is a
description of the shoreline public use facilities at Lake Powell.
Wahweap – The facilities at Wahweap are the closest to Glen Canyon Dam, located off
Interstate 89 at the mouth of Wahweap Bay. According to a study that addressed
fluctuating lake levels and recreation use, the Stateline Launching Ramp at Wahweap
became inoperable in 1989 when the lake elevation decreased to below 3677 feet msl
(Combrink and Collins 1992). In 1993, NPS extended the Wahweap and Stateline boat
ramps down to an operable level of 3612 feet msl (Henderson, 2000).

erior

Dangling Rope Marina – The facilities at Dangling Rope Marinant proposed to
e I were
of th All 2 17
. Canyon. 29,the0facilities float,
t
replace the facilities at Rainbow Marina in Forbidding
Dep addition r
e
and they are only accessible by boat (NPS, 1979). In vemb to the facilities, tour
n v.
atiofor visits to Rainbow Bridge National
No
boats depart from Dangling Rope Marina ed on
jo N
Nava seasoniv
n
Monument during the irecreation, arch (NPS, 1993). There are no known reservoir
cited would64
surface elevations that -168 impair operation of this facility.

No.

14

Halls Crossing – The facilities at Halls Crossing are located off Utah Highway 276 on
the east shore of Lake Powell, across the bay from Bullfrog Marina. According to a
study that addressed fluctuating lake levels and recreation use, the Halls Crossing Ferry
Ramp became inoperable in 1989 when the lake elevation decreased to below 3675 feet
msl (Combrink and Collins, 1992). In 1993, NPS extended the boat ramp down to an
operable level of 3612 feet msl (Henderson, 2000).
Bullfrog – The facilities at Bullfrog are located midway up Bullfrog Bay, off of Utah
Highway 276 and across the bay from Halls Crossing. According to a study that
addressed fluctuating lake levels and recreation use, the Bullfrog Ferry Ramp became
inoperable in 1989 when the lake elevation decreased to below 3675 feet msl. In
addition, the Bullfrog Utility Service became inaccessible when the lake elevation
decreased to below 3670 feet msl (road access was also unavailable at the slips)
(Combrink and Collins, 1992). In 1993, NPS extended the boat ramp down to an
operable level of 3612 feet msl (Henderson, 2000).

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Table 3.9-2
Lake Powell Shoreline Public Use Facilities

Facility

Wahweap

Dangling
Rope
Marina

Halls
Crossing

Bullfrog

Hite

Antelope
Point *

Lodging (rooms)

375

N/A

20

56

5

200-225

Restaurant/Snack
Bar

2/1

N/A/1

•/1

1/1

N/A

•

Tour boats

9

N/A

N/A

1

N/A

2

Boat slips

870

N/A

165

254

6

250-300

Mooring buoys

180

N/A

141

220

54

N/A

Rental houseboats

175

N/A

89

112

21

60

Rental small boats

150

N/A

44

50

27

60

Dry storage

450

N/A

230

750

109

•

RV park (spaces)

120

N/A

32

24

N/A

150

Marina campstore

1

1

1

1

N/A

1

Store

•

•

1

1

1

1

Boat repair

•

•

•

•

N/A

N/A

gas r
r
t150io
Parking (spaces)
2,500
N/A
300
1,575 e In e
h
017
ft
Campground (sites)
215
N/A
64
100
6
pt. o er 29, 2
. De e50 b
m
Picnic (sites)
124
N/A ion v20
N/A
Nat d N/A Nov N/A
n
Day use
N/A
N/A
vajoN/A e o
beaches/trails
in Na 4, archiv
c ed 2 686 N/A
Launching ramps it
1
1
1
-1
. 14N/A
Airstrip
N/A
N/A
3,5002,100-foot,
No
Service station

•

•

gas

•

foot,
paved

•
220
•
N/A
•
1
N/A

paved

Visitor center,
cultural center

•

N/A

N/A

N/A

N/A

Ranger station

•

N/A

•

•

N/A

•

Employee housing

•

•

•

N/A

•

•

Concessionaire
quarters

80

N/A

30

40

10

N/A

Dorm units

119

6

24

96

0

N/A

7,80010,100

2,4003,100

3,4004,400

7,90010,300

2,5003,300

N/A

Capacity (use per
day)

•

Source:
2000.

NPS 1979. Proposed General Management Plan and personal communication, Norm Henderson, NPS,

•

indicates presence of an improvement.

N/A

not applicable – indicates no improvement.

*
Facilities shown are proposed. Existing facilities include an entrance station, gravel parking area, two
permanent toilets, and a boat ramp. The Navajo Nation and NPS are in the process of developing the site.

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Hite – The facilities at Hite are located off of Utah Highway 95. According to a study
that addressed fluctuating lake levels and recreation use, the Hite Launching Ramp
became inoperable in 1989 when the lake elevation decreased to below 3677 feet msl
(Combrink and Collins 1992). In 1993 NPS extended the boat ramp down to an
operable level of 3612 feet msl. However, the ramp area is known to be useable down
to 3630 feet msl (Henderson, 2000).
Antelope Point – The facilities at Antelope Point are located off of Arizona Highway 98
on the southern side of Lake Powell. Development of Antelope Point only began
recently, and data on visitation has not been collected on a formal basis. Existing
facilities at the site consist of an entrance station where fees are collected, two
permanent toilets, a large gravel parking area that can accommodate 220 vehicles, and a
public boat ramp. The Navajo Nation, in conjunction with NPS, has plans to develop
the site as a resort destination, and is in the process of selecting a master developer for
the project. Facilities proposed for the site in the Development Concept Plan are listed
in Table 3.9-2, above.
The existing boat ramp at Antelope Point currently extends down to 3677 feet msl. NPS
provided Reclamation with construction drawings for extending the boat ramp down to
3620 feet msl as water elevation declines. The extended boat ramperior allow
would
Int 36257 msl,
houseboats and other watercraft to launch down to elevations e
f th around 01 feet
pt o er 29, 2
assuming about 5 feet of free board (Bishop, Personal .Communication, 2000). NPS
. De
b
also provided Reclamation with a preliminary Antelopeem Marina layout drawing
ion v Nov Point
at
for reservoir elevation of 3600ajo N ved on not been established that a marina
v feet msl, but it has
in Na 4, archi
would be operableed this level.
t at

ci
1686
. 14- Monument – The Rainbow Bridge National Monument is
Rainbow Bridgeo
N National

located on the south shore of Lake Powell and is bounded on three sides by the Navajo
Reservation near the Utah/Arizona border. The facilities at the monument include
courtesy docks, restrooms, a floating walkway, and a floating interpretive platform.
Trails from the dock lead to viewing areas. One viewing area is used when Lake Powell
is below the full-pool elevation of 3700 feet msl, and the other is used when the
reservoir is at full-pool elevation. The docks and trail system are designed to
accommodate lake level fluctuations allowed in the operation of Glen Canyon Dam and
powerplants (from 3490 feet msl to 3700 feet msl) (NPS, 1993). If the lake levels fall
below 3650 feet msl, the dock facilities would be moved and the old land trail through
Bridge Canyon (submerged at full pool) would be hardened and used for access. The
floating walkway and interpretive platforms would be removed and stored. The
courtesy docks would be connected to the land trail with a short walkway (NPS, 1990).
However, large quantities of silt that have been deposited where Bridge Creek flows
into Lake Powell could create access problems at low water surface elevations. The
large silt flats are difficult to cross with floating walkways; special construction
techniques may be required to bridge these areas. At some lake elevations, it may be
infeasible to maintain water access to the monument (NPS, 1993); however, the specific
elevation is not known.

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When Lake Powell is operated below 3700 feet msl, some of the Rainbow Bridge
National Monument is within a high hazard flash flood area. The 100- and 500-year
flood elevations in Bridge Creek are estimated to be 7.5 feet and 10 feet above the creek
channel, respectively. For the area well upstream of Lake Powell, the trail follows the
creek and is above both the 100- and 500-year floodplains. However, the trail route in
the transition zone between the reservoir and creek, along the lake’s edge, could be
subject to water surface elevation increase, surface turbulence, and significant
velocities, depending on the lake elevation at the time of flooding and the magnitude of
the flood. For the lake itself, there would be little or no discernable water surface
increase and the turbulence would be limited. When Lake Powell is at full operating
pool, flash flood areas are well upstream of the reservoir, in the Bridge Creek Canyon
drainage outside the monument.
The General Management Plan for Rainbow Bridge includes a Flash Flood Mitigation
Plan. In the event of combined low pool elevations and flash flood conditions, there are
four components of the mitigation plan that would be put in place. These components
include: 1) a wayside exhibit with information to inform visitors of possible flash flood
hazards; 2) additional signage in the flood hazard zones to alert visitors where to move
in case of a flood; 3) identification of evacuation and emergency measures, including
chain of command responsibilities, emergency supply locations, and rior
nte support facilities;
and 4) installation of a warning system that would alert of the to evacuate.
visitors I
2017

,
t.
Dep
er 9
. access to mbarea2was primarily by foot.
Prior to the construction of Glen Canyonon v
ati Dam, Nove the
Since the creation of Lake Powell, access ed on primarily by water, although the area
ajo N iv is now
Nav
is also accessible tby trails througharch Mountain. Access to the monument is
d in 64, Navajo
ci e 168
restricted during the recreation season in accordance with the monument’s carrying
14capacity of 200 people at one time. In addition, access is limited daily during certain
No.

times of the day. Boat tours to the monument are allowed during the busier time of the
day and originate at Dangling Rock Marina. All tours have an NPS interpreter on board
to convey the monument’s significance. Access during quieter times of the day is
limited to five to eight private boats. During the off-season, access to the monument is
unrestricted except that boat tours are managed to ensure that only one tour boat at a
time is present at the monument (NPS, 1993).
3.9.2.2.2.1 Threshold Elevations
From the information presented above on reservoir pool elevations, three elevations,
3677 feet msl, 3626 feet msl and 3612 feet msl, were identified as representative
threshold elevations below which shoreline facilities at Lake Powell could be affected.
The existing boat ramp at Antelope Point extends down to elevation 3677 feet msl. This
elevation is identified as one of the threshold elevations for the analysis of marinas and
boat ramps at Lake Powell. As discussed above, the extended boat ramp would be
operable down to 3625 feet msl. The elevation of 3626 feet msl is discussed in the
boating navigation and safety section (Section 3.9.3.3.1) and is considered to be

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representative of the threshold elevation for the extended boat ramp. Since the
minimum reservoir elevation at which the Antelope Point Marina would be operable has
not yet been established, the threshold elevations of 3626 feet msl (discussed above)
and 3612 feet msl (discussed below) are assumed to apply to a future marina at
Antelope Point.
As discussed above, the boat ramps at Wahweap, Halls Crossing, Bullfrog, and Hite are
designed to operate down to 3612 feet msl. It is not known what adjustments and
capital improvement costs would be required if elevations were to decline to below
3612 feet msl. As such, 3612 feet msl is used in this analysis as the lower threshold
elevation for marinas and boat ramps at Lake Powell.
The threshold elevations of 3677 feet msl, 3626 feet msl and 3612 feet msl are used to
evaluate baseline conditions and the effects of interim surplus criteria alternatives on
shoreline facilities at Lake Powell in the Environmental Consequences section
(Section 3.9.2.3.1). The threshold elevation of 3626 feet msl is evaluated in Section
3.9.3.3.1.
3.9.2.2.3 Lake Mead Recreation Resources

rior

e
Lake Mead, the reservoir created by the construction of Hoover IDam, is located in the
e nt
7
f thNevada 201northern
Lake Mead National Recreation Area (LMNRA) in pt. o
southern
29, and
r
. De
Arizona. The LMNRA contains 1.5 million acres andvembe
ion v No encompasses the 100-mile-long
Nat
Lake Mead, 67-mile-long Lake Mohave, the surrounding desert, and the isolated
vajo fullhived on of approximately 1210 feet msl,
Shivwits Plateau in d in Na At aarc pool elevation
Arizona.
cite 1 is 64,
Lake Mead’s surface area68153,235 acres, the storage capacity is 25.9 maf and there
are 695 miles of o. 14 (USBR, 1996b). Lake Mead is the largest man-made lake in
N shoreline
the Western Hemisphere.
LMNRA receives approximately ten million visitors annually. Typical water-based
recreation activities that occur on Lake Mead include: swimming, boating,
houseboating, fishing, sailboarding, paddlecraft use, scuba diving (USBR, 1996b). On
average, the majority of boats are personal watercraft. There may be as many as 6000
boats combined on Lake Mead and Lake Mohave during a peak recreation use weekend.
At Boulder Beach, which is located near the urbanized area of Las Vegas and
surrounding communities, the personal watercraft percentage may be as high as 50
percent.
3.9.2.2.4 Shoreline Public Use Facilities at Lake Mead
Six marinas at Lake Mead provide boat launching facilities as well as slips and storage,
fuel and boat launches. In addition, there are three boat ramps without associated
marinas and one site without a boat ramp. The marinas include Boulder Beach, Las
Vegas Bay, Calville Bay, Echo Bay, Overton Beach and Temple Bar. The boat ramps
are located at Hemenway, Government Wash and South Cove. Pearce Ferry has no

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boat ramp and is used as a take out by private and commercial boaters that kayak and
raft the Colorado River into Lake Mead. Facilities at the six marinas are summarized in
Table 3.9-3, and all of the sites are described below. If the actual number of
improvements (boat slips, etc.) at the facility is known, it is included in the table;
otherwise, the presence of an improvement is indicated with a bullet (•). If there are no
facilities at a location, this is indicated with an “N/A” for “not applicable.” Map 3.9-2
shows the locations of both developed and undeveloped sites on Lake Mead.
Table 3.9-3
Lake Mead Marina Public Use Facilities
Boulder
Beach/ Lake
Mead Marina

Las
Vegas
Bay

Calville
Bay

Echo
Bay

Overton
Beach

Temple
Bar

Lodging

•

N/A

N/A

•

N/A

•

Restaurant

•

•

•

•

•

•

Facility

•

N/A

N/A

N/A

N/A

N/A

Marina (boat slips)

750

•

650

320

•

•

Mooring buoys

N/A

N/A

N/A

N/A

N/A

N/A

N/A

•

•

N/A

N/A

Tour boats

N/A
or
teriN/A
•
• In
th•e
017
Dry storage
•
•
•pt. of
29, 2 •
De
er
RV Park (spaces)
N/A
N/An v. N/A emb
58
N/A
v
io
Nat d on No
Trailer village
N/A
69
o
•
•
•
avaj rchN/Ae
iv
Trailer sewage dump d in N •
•
•
•
a
cite 16864,
Grocery/gift store
•
•
•
•
- •
o. 14
N
Gasoline/Propane
N/A
•
•
•
•

Rental houseboats

N/A

Rental small boats

N/A
•
•
7
111
•
•
•

•

•

•

•

•

•

Parking (spaces)

N/A

N/A

N/A

N/A

N/A

N/A

Campground (sites)

Boat sewage dump

154

89

80

166

N/A

153

Picnic (sites)

•

•

•

N/A

N/A

N/A

Showers

•

N/A

•

•

•

•

Launching ramps

•

•

•

•

•

•

N/A

N/A

N/A

•

N/A

•

Airstrip
Ranger station

•

•

•

•

•

•

Self-service laundry

•

N/A

•

•

•

•

N/A

N/A

N/A

N/A

N/A

N/A

Capacity (use per day)
Source: NPS, 1995
•

indicates presence of an improvement

N/A

not applicable – indicates no improvement

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-10

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-11

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Map 3.9-2
Lake Mead and Associated Shoreline Recreation Facilities

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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Recreation boating is very popular at Lake Mead, and the shoreline public use facilities
are associated with boating use. Most of the facilities shown in the Table 3.9-3 were
designed to operate at full pool. However, NPS has determined costs associated with
adjusting facilities based on lowered lake elevations. These facilities are out of their
normal operating range at pool elevations of 1180 feet msl, requiring sizable capital
expenditures to restore them to working order. In addition, there are additional costs
associated with any 20-foot drop below this level.
Hemenway – The boat ramp facility at Hemenway is the closest to Hoover Dam and is
located off Nevada Highway 166. There is one courtesy dock and a parking area
(Henderson, 2000). In addition, campgrounds and a group campground are located at
Hemenway. The group campground is for self-contained vehicles, such as trailers and
motor homes. There are no restrooms or tables.
Boulder Beach – The facilities at Boulder Beach are located off of Lakeshore Scenic
Drive, just off of Nevada Highway 167 outside of Boulder City, Nevada, and include
restrooms, tables and grills. There is also a group campground at Boulder Beach for
tent camping only with limited vehicle parking.
Las Vegas Bay – The facilities at Las Vegas Bay are located off Lakeshore Scenic
ior
Inter 17
Drive, just off Lake Mead Drive (Nevada Highway 167). According to a marina
0
f the
worker, when the lake elevation drops below 1190 feet msl, the boat ramps and floats
pt. o er 29, 2
e
v. D vemb
have to be readjusted.
tion
o

N
Na
vajo facilityd on
e at Government Wash is located off Nevada
Government Wash – TheNa ramprchiv
d in boat , a
Highway 167. cite is 16864
There - one courtesy dock and a parking area (Henderson, 2000).
14
No.

Calville Bay – The facilities at Calville Bay are located off Nevada Highway 167 on the
north shore of Lake Mead, midway up Calville Bay.
Echo Bay – The facilities at Echo Bay are located off Nevada Highway 167, midway up
Overton Arm.
Overton Beach – The facilities at Overton Beach are located off Nevada Highway 169,
near the top of Overton Arm.
South Cove – The boat launching facilities at South Cove are located off Aztec Wash,
which is off Interstate 93 in Arizona. There is one courtesy dock, picnic facilities, and
unpaved parking (Henderson, 2000). In addition, there is an airstrip approximately four
miles from the facilities at South Cove (Henderson, 2000).
Temple Bar – The facilities at Temple Bar are located on the south shore of Lake Mead
at the end of an unnamed road off Interstate 93 in Arizona.
Pearce Ferry - This area is located near Aztec Wash, which is off Interstate 93 in
Arizona at the eastern end of the LMNRA. The area is a large, gravel wash with a

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gentle slope down to the water. Vehicles are driven down to the water’s edge to load
rafts and other small boats. There is parking and a year-round portable toilet, and
primitive camping is allowed. There are no ramps, docks or other developed facilities
at the site.
The Hualapai River Runners are one of the commercial guide services that use Pearce
Ferry as a take out. The River Runners conduct guided whitewater trips that put in at
Diamond Creek, and float trips that put in at Quartermaster Canyon. All of these trips
take out at Pearce Ferry.
Comments from the Hualapai Tribe on the Draft EIS identified a Lake Mead pool
elevation of 1183 feet msl as a threshold elevation for accessing the Pearce Ferry
takeout. At this elevation and below, the river subdivides into smaller channels and
large areas of silt and mud are exposed, prohibiting access to the take out.
When Pearce Ferry is inaccessible as a takeout, boaters must continue downstream to
South Cove, an additional 16 miles. This costs river runners fuel (for motorized craft),
time (one to two more hours on the river) and possible safety problems (due to fatigue).
For commercial boaters, the additional travel time to South Cove can also result in lost
business by preventing guides from meeting river tour schedules. rior

Inte
f the 9, 2017
3.9.2.2.4.1 Threshold Elevations
pt. o
. De ember 2
nv
v
Natio d on N pool elevations where facilities or
The description of facilities above identifies several o
ajo
access to facilities would Naaffected. hive Vegas Bay, 1190 feet msl was identified
be v
Las
d in facilities arc Atrequire adjustment, but would continue to be
e
itwhich 6864, would
as an elevation c
at
-1
operable. Elevation14 feet msl was identified by the NPS as the elevation at which
o. 1180
N

most other developed facilities would require capital expenditures, rather than just an
adjustment, in order to maintain operation. Elevation 1183 feet msl was identified by
the Hualapai Tribe in their comments on the DEIS as a threshold elevation for using the
undeveloped Pearce Ferry site as a takeout for rafts and other whitewater boats.
The DEIS evaluated the consequences of elevation 1180 feet msl for facilities at Lake
Mead (Section 3.9.2.3.2). In response to the Hualapai Tribe’s comment on the DEIS
regarding the threshold elevation of 1183 for Pearce Ferry, this FEIS evaluates the
consequences of 1183 feet msl instead of 1180 feet msl. Therefore, 1183 feet msl is
used as a representative threshold elevation for shoreline facilities and public access at
Lake Mead and is used in the Environmental Consequences section (Section 3.9.2.3.2)
to evaluate the effects of baseline conditions and interim surplus criteria alternatives on
shoreline facilities and public access at Lake Mead.
3.9.2.3 ENVIRONMENTAL CONSEQUENCES
Recreational boating on Lake Mead and Lake Powell is dependent upon access to the
water via public shoreline facilities such as marinas, docks and boat ramps, as well as

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undeveloped launch areas. Some fluctuation in water level is a normal aspect of
reservoir operations, and facilities are designed and operated to accommodate it.
However, decreased pool elevations or increased variations or rates in pool elevation
fluctuation could result in increased operation costs, facility improvements, temporary
closures, or possibly permanent closure of shoreline facilities.
As lake levels fluctuate, developed facilities must be adjusted accordingly. This could
require moving and relocating docks, extending utility lines associated with shoreline
facilities, increasing sewage pump capacity, reducing pressure on water supply lines to
boats, adjusting and relocating buoys, moving breakwater barriers and channel markers,
and extending launch and dock ramps (Combrink and Collins, 1992). If lake
fluctuations exceed 25 feet, special adjustments to lake facilities would be necessary,
including the relocation of anchors and the extension or reduction of utility lines and
cables that provide utility service to floating facilities (Combrink and Collins, 1992).
In addition, if developed facilities are temporarily or permanently closed or relocated, or
undeveloped sites are no longer accessible, there may be associated increases in
reservoir boating congestion or longer wait times at sites that remain open. This could
have an effect on boating satisfaction. The cost of relocating developed facilities in
response to changes in reservoir pool elevations is discussed in Section 3.9.6.
erior

Int
f the 9, 2017
3.9.2.3.1 Lake Powell
pt. o
. De ember 2
nv
ov
Natio d on above, pool elevations of 3677 feet
As discussed in the Affected Environment sectionN
ajo
i
N v arc asve
msl and 3612 feet msliwerea
d n identified h representative thresholds that are problematic
ite at Lake 4,
c
for shoreline facilities -1686 Powell. Elevation 3677 feet msl was identified as a
threshold elevation 14 the existing Antelope Point, and the NPS identified 3612 feet
No. for

msl as a threshold for several other facilities. These are elevations below which facility
adjustments or capital improvements would be required.
There are two other threshold elevations not treated directly below. Elevation 3626 feet
msl has also been defined as a threshold elevation for the design boat ramp at Antelope
Point. This elevation is discussed in Section 3.9.3.3.1. Facilities at Rainbow Bridge
would be affected by pool elevations of 3650 feet msl or below, as described above in
Section 3.9.2.2. Although specific probabilities of remaining above elevation 3650 feet
msl were not determined, the probabilities that lake elevations would remain above
3650 feet msl would be between the probabilities for the threshold elevations of 3677
and 3612 feet msl, which are discussed below.
Figure 3.9-1 provides an overview of the differences in end-of-July water surface
elevation trends under baseline conditions and the action alternatives over the period of
analysis.
Figure 3.9-2 and Table 3.9-4 indicate the probability of Lake Powell elevation
exceeding the threshold of 3677 feet msl in July. The probability would decrease the

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-14

3500
2000

3520

3540

3560

3580

3600

3620

3640

3660

3680

3700

3720

2005

2010

2015

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

2020

3.9-15

Year

2025

2030

2035

2040

10th Percentile

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
50th Percentile

90th Percentile

Figure 3.9-1
Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
th
th
90 , 50 and 10th Percentile Values

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Surface Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2045

3612

3626

3650

3677

2050

CHAPTER 3

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0%
2000

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2005

2010

2015

2020

3.9-16

Year

2025

2030

2035

2040

2045

ior
Shortage
Inter Protection Alternative
e
of th 29, 2017
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.9-2
Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 3677 Feet msl

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

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most over the initial 15 years of the period of analysis. During this time, the probability
would decline from nearly 80 percent to less than 40 percent under baseline conditions
and the alternatives. During years 16 through 25 the effects of the alternatives would
diminish, although the probability of exceeding elevation 3677 feet msl would remain
low (roughly 30-40 percent). After year 25 there would be no discernable effect of the
alternatives for the remainder of the analysis period; the probability of exceeding
elevation 3677 feet msl would remain fairly low at around 40 to 45 percent.
The differences between the alternatives would be most apparent during the first 15
years. The greatest difference occurs in year nine, when the difference between
baseline conditions and the Shortage Protection Alternative is 19 percent. The Flood
Control Alternative, with results that are nearly identical to those of baseline conditions,
has the lowest probability of pool elevations dropping below 3677 feet msl, whereas the
Shortage Protection and California alternatives have the highest probability. The Basin
States and Six States alternatives have probabilities between the baseline conditions and
the Shortage Protection Alternative.
Table 3.9-4
Probabilities of Lake Powell Elevation Exceeding 3677 feet in July

ior
Inter 17
f the
20
Alternative
pt.- o er 29, – 49
e 16 25 b Years 26
Years 1-15 v. D
Years
m
ation on Nove
N
Baseline Conditions
46%-40%
vajo79%-39% d 40%-34%
e
in Na 4, archiv
Basin States Alternative 686
78%-36%
39%-34%
46%-40%
cited 1
. 14No
Flood Control Alternative
79%-39%
40%-35%
46%-40%
Range of Probability

Six States Alternative

78%-36%

39%-34%

46%-40%

California Alternative

75%-33%

40%-34%

46%-40%

Shortage Protection Alternative

75%-33%

39%-34%

46%-40%

The probability of Lake Powell pool elevation exceeding the threshold of 3612 feet msl
in July under baseline conditions and each of the alternatives is shown in Figure 3.9-3
and Table 3.9-5. The probability is greater than 70 percent throughout the period of
analysis. The probability begins at 100 percent, due to the relatively full initial
elevation, and declines gradually throughout the period of analysis. In general,
probabilities decrease within a 10 to 15 percent range during the initial 15-year period,
followed by an additional 10 to 15 percent decrease from years 16 through 34. For the
remainder of the analysis period, decreases are around 5 percent.
The differences between the alternatives is slight, with the greatest difference in
probabilities being about eight percent. The Flood Control Alternative has the same

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

probabilities as baseline conditions and therefore would have no effect. The other
alternatives have probabilities less than or equal to baseline conditions. The Shortage
Protection and California Alternatives have effects similar to each other and result in
the greatest departure (maximum eight percent) from baseline conditions. The Six
States and Basin States alternatives are between the Shortage Protection Alternative and
baseline conditions, and have a maximum departure of five percent from baseline
conditions.
Each of the alternatives is discussed below in more detail with respect to the patterns
indicated on Figures 3.9-2 and 3.9-3 and Tables 3.9-4 and 3.9-5.
Table 3.9-5
Probabilities of Lake Powell Elevation Exceeding 3612 feet in July

Range of Probability
Alternative
Years 1-15
Baseline Conditions

Years 16-34

Years 35-49

100%-91%

88%-76%

78%-72%

76%-72%
r
terio
In 78%-72%
Flood Control Alternative
100%-91%
88%-76%
017
f the
pt. o er 29, 2
. De 87%-75%
b
Six States Alternative
100%-88%
76%-72%
ion v Novem
at
N
n
jo
California Alternative ava
100%-87%
85%-75%
76%-72%
ed o
in N 4, archiv
d
6
cite 1 Alternative
Shortage Protection68
100%-86%
84%-75%
76%-72%
. 14o
N
Basin States Alternative

100%-88%

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-18

86%-75%

70%
2000

75%

80%

85%

90%

95%

100%

2005

2010

2015

2020

3.9-19

Year

2025

2030

2035

2040

California Alternative

2045

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

2050

CHAPTER 3

ior
Inter Protection Alternative
e Shortage
of th 29, 2017
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

Figure 3.9-3
Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 3612 Feet msl

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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CHAPTER 3

3.9.2.3.1.1 Baseline Conditions
The probability under baseline conditions that Lake Powell pool elevation is above
3677 feet msl in July decreases from 79 percent in year 1 to 39 percent in year 15. In
years 16 through 25, the probability ranges between 40 and 34 percent. For the
remainder of the analysis period the probability ranges between 40 and 46 percent. The
early declining probabilities (for baseline conditions and alternatives) can be mostly
attributed to increasing consumptive use of Colorado River water in the Upper Basin.
The later rise is attributed to the suspension of equalization requirements between Lake
Powell and Lake Mead (see Section 1.4.2).
There is a high probability that July Lake Powell pool elevation would exceed the
threshold of 3612 feet msl for the baseline condition throughout the period of analysis.
Between years 1 and 15, the probability decreases from 100 percent to 91 percent.
Between years 16 and 34, the probability continues to decrease gradually from
88 percent to 76 percent. For the remainder of the analysis period, the probability
decreases slightly, ranging between 78 and 72 percent. The declining trend of all
probabilities (baseline conditions and alternatives) can be mostly attributed to
increasing consumptive use of Colorado River water in the Upper Basin.

ior
Inter 17
3.9.2.3.1.2 Basin States Alternative
0
f the
pt. o er 29, 2
e
The probability of the Lake Powell poolion v. D exceeding 3677 feet msl in July is
elevation
mb
at
Nove baseline conditions. In the
slightly lower under the Basin ajo NAlternative than under
States
on
ved
Nav archifrom 78 percent to 36 percent under the Basin
first 15 years, the probability decreases
in
,
cit d probability
States Alternative.eThe 16864 during this period is one percent to eight percent
14lower than under baseline conditions. In years 16 to 25, the probability decreases to a
No.
low of 34 percent, then rises to 39 percent. During this period, the probability is
generally the same as for baseline conditions. For the remainder of the analysis period,
probabilities fluctuate between 40 and 46 percent, and are generally the same as under
baseline conditions.

The probability of Lake Powell elevation exceeding 3612 feet msl in July under the
Basin States Alternative is slightly lower than for the baseline conditions. Between
years 1 and 15, the probability decreases from 100 percent to 88 percent, compared to a
91 percent probability under baseline conditions. During this period, the probability is
typically up to two percent less than under baseline conditions. Between years 16 and
34, the probability continues a gradual decline to 75 percent, and ranges between zero
and five percent less, but typically between zero and two percent less, than under
baseline conditions. For the remaining years of analysis, the probability continues to
decline to a low of 72 percent in year 2050, and is within one percent of the probability
under baseline conditions.

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CHAPTER 3

3.9.2.3.1.3 Flood Control Alternative
The probability of Lake Powell pool elevation exceeding 3677 feet msl under the Flood
Control Alternative is approximately the same as for baseline conditions. In the first 15
years, the probability decreases from 79 to 39 percent, and is within one percent of the
probability under baseline conditions. From years 16 to 25, the probability fluctuates
between 40 and 35 percent. The probability during this period is typically the same as
under baseline conditions. By the end of the period of analysis, the probability remains
fairly constant, between 40 and 46 percent. During this period, the probability is
typically the same as under baseline conditions.
The probability of Lake Powell pool elevation exceeding 3612 feet msl under the Flood
Control Alternative is generally the same as that described for baseline conditions
throughout the period of analysis.
3.9.2.3.1.4 Six States Alternative
The probability of Lake Powell pool elevation exceeding 3677 feet msl under the Six
States Alternative is very similar to the Basin States Alternative discussed above. In
early years, the probability is up to seven percent less than under baseline conditions.
rior
In later years, the probability is generally the same as under he Inte conditions.
baseline
7

01
of t
29, 2
ept. 3612rfeet msl under the Six
The probability of Lake Powell pool elevation.exceedingmbe
v D
ation BasinNove Alternative. In early years, the
States Alternative is also very similar to the on States
jo N
Nava ar than ed
probability is up to four percent less chivunder baseline conditions. In later years, the
in
cited 16864
probability is typically the same ,as under baseline conditions.
14No.
3.9.2.3.1.5 California Alternative
The probability of Lake Powell pool elevation exceeding 3677 feet msl is lower under
the California Alternative than under baseline conditions. In the first 15 years, the
probability declines from 75 percent to a low of 33 percent, and ranges from 4 to 16
percent less than under baseline conditions. In years 16 to 25, the probability increases
slightly, ranging from 34 to 40 percent, and is typically the same as under baseline
conditions. For the remainder of the analysis period, the probability increases slightly,
remaining between 40 and 46 percent, and is always within one percent of baseline
conditions.
The probability of Lake Powell pool elevation exceeding 3612 feet msl under the
California Alternative is slightly lower than under baseline conditions. Between years 1
and 15, the probability decreases from 100 percent to 87 percent and is from zero to
eight percent less than under baseline conditions. The probability continues to decrease
from 85 to 75 percent in years 16 through 34, and is up to seven percent less than under
baseline conditions. For the remaining years of analysis, the probability ranges between
76 and 72 percent, and is from zero to two percent less than under baseline conditions.

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CHAPTER 3

3.9.2.3.1.6 Shortage Protection Alternative
The probability of Lake Powell pool elevation exceeding 3677 feet msl under the
Shortage Protection Alternative is not significantly different from the California
Alternative discussed above. In early years, the probability is up to 19 percent less than
under baseline conditions. In later years, the probability is typically the same as under
baseline conditions.
The probability of Lake Powell pool elevation exceeding 3612 feet msl under the
Shortage Protection Alternative is not significantly different from the California
Alternative discussed above. In early years, the probability is up to eight percent less
than under baseline conditions. In later years, the probability is within two percent of
the probability under baseline conditions.
3.9.2.3.2 Lake Mead
As discussed in the Affected Environment section above, a pool elevation of 1183 feet
msl was identified as a representative threshold that is problematic for shoreline access
at Lake Mead. Figure 3.9-4 provides an overview of the difference in end-of-year water
surface elevations under baseline conditions and each of the action alternatives.
ior
Inter 17
Although elevations would typically be lower during the summer peak-use period, the
0
f the
differences between baseline conditions and action alternatives would be similar to
pt. o er 29, 2
e
.D
b
those presented herein.
vem
ion v

Nat d on No
vajo the probability of Lake Mead elevation exceeding
Figure 3.9-5 and Tablen Na indicate hive
i 3.9-6
arc
ited feet6864,the end of the year. As shown in Figure 3.9-5, the
c
the threshold of 1183
msl at
-1
probability is low . 14 the period of analysis due primarily to effects associated with
o over
N
baseline conditions. In the initial 15 years of analysis, the probabilities under baseline
conditions and the alternatives decline by more than 20 percent. Shortly after year 15,
the probabilities under baseline conditions and the alternatives converge near 35
percent. Subsequently, a probability of 28 to 36 percent is maintained until the end of
the analysis period.
Table 3.9-6
Comparison of Lake Mead Elevation Exceedance Probabilities for Elevation 1183 Feet
Alternative

Year 0-15

Years 16 - 49

Baseline Conditions

65%-36%

36%-29%

Basin States Alternative

55%-32%

35%-29%

Flood Control Alternative

65%-36%

38%-29%

Six States Alternative

55%-32%

35%-29%

California Alternative

45%-25%

35%-28%

Shortage Protection Alternative

47%-26%

34%-28%

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-22

1000
2000

1020

1040

1060

1080

1100

1120

1140

1160

1180

1200

1220

2005

2010

2015

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

2020

3.9-23

Year

2025

2030

2035

2040

10th Percentile

ior
Inter 17
e
of th 50th9, 20
Percentile
pt.
. De ember 2
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

90th Percentile

Figure 3.9-4
Lake Mead End of December Water Elevations
Comparison of Surplus Alternative to Baseline Conditions
th
th
th
90 , 50 and 10 Percentile Values

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Water Elevation (feet)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2045

1170

1183

2050

CHAPTER 3

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0%
2000

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2005

2010

2015

2020

3.9-24

Year

2025

2030

2035

2040

2045

or
nteri 7
IStates Alternative
e
of th Six 29, 201
pt.
California Alternative
. De ember
v
n
Shortage Protection Alternative
Natio d on Nov
jo
Nava archive
in
cited 16864,
o. 14
N
Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.9-5
Lake Mead End of December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percent of Values Greater than or Equal to 1183 Feet msl

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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3.9.2.3.2.1 Baseline Conditions
The probability of Lake Mead pool elevation exceeding 1183 feet msl declines from 65
percent to 36 percent under baseline conditions during the first 15 years of the analysis
period. In the remaining years of the analysis period, the probability ranges between 36
and 29 percent. The general declining trend of Lake Mead elevations over time can be
attributed to increases in Upper Basin use.
3.9.2.3.2.2 Basin States Alternative
The probability of Lake Mead pool elevation exceeding 1183 feet msl in the first 15
years of the analysis period declines from 55 percent to 36 percent under the Basin
States Alternative. The probability during this period is typically up to nine percent less
than under baseline conditions. In remaining years of the analysis period, the
probability ranges between 35 and 29 percent. During this period, the probability is
within one percent of the probability under baseline conditions.
3.9.2.3.2.3 Flood Control Alternative
The probability of Lake Mead pool elevation exceeding 1183 feet msl inr the first 15
io
years of the analysis period declines from 65 percent to 36 percenttunder the Flood
In er 17
he the probability ranges
20
Control Alternative. In remaining years of the analysis of t
ept. period,r 29,1183 feet msl under
D
be
between 38 and 29 percent. The probability v. exceeding elevation
on of Novem
atiapproximately the same as under baseline
the Flood Control Alternative would be
ajo N
d on
conditions throughout itheNav analysisvperiod.
entire rchi e
n

a
cited 16864,
14
3.9.2.3.2.4 Six States No. Alternative

The probability of Lake Mead pool elevation exceeding 1183 feet msl in the first 15
years of the analysis period declines from 55 percent to 32 percent under the Six States
Alternative. In remaining years of the analysis period, the probability ranges between
35 and 29 percent. The probability is nearly identical to that for the Basin States
Alternative discussed above.
3.9.2.3.2.5 California Alternative
The probability of Lake Mead pool elevation exceeding 1183 feet msl is lowest under
the California Alternative in most years. In the first 15 years, the probability ranges
between 45 and 25 percent. This is up to 26 percent lower than under baseline
conditions. After year 16, the probability is within one percent of the probability under
baseline conditions.

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3.9.2.3.2.6 Shortage Protection Alternative
The probability of Lake Mead pool elevation exceeding 1183 feet msl under the
Shortage Protection Alternative is nearly the same as under the California Alternative.
In the first 15 years, the probability ranges between 47 and 27 percent and is up to 26
percent lower than under baseline conditions. After year 16, the probability associated
with the Shortage Protection Alternative generally converges with baseline conditions
and the other alternatives, similar to the California Alternative.
3.9.3

RESERVOIR BOATING/NAVIGATION

This section discusses potential effects of the interim surplus criteria on reservoir
boating and navigation. This includes a discussion of areas on the reservoir that could
become unsafe for boating at certain elevations due to exposed rocks or other
obstructions, and safe boating densities that indicate the number of boats that can safely
be accommodated on the reservoirs at one time.
Boating navigation and safe boating capacities on Lake Powell and Lake Mead are
dependent upon water surface elevations. As lake levels decline, so does the available
surface area. Hazards such as exposed rocks may become more evident,r or changes in
rio for
navigation patterns may be necessary. The area of the reservoirsnte
he I available7 boating is
t
201
also reduced, which may affect the number of boatspt. of safely operate at one time.
e that can er 29,
At low pool elevations, special buoys orion v. Dmayvemb to warn boaters of
markers
o be placed
Nat d o placed
navigational hazards. In addition, signs may ben N in areas that are deemed
vajo hive
unsuitable for navigation.Na
in
arc
d

cite 16864,
143.9.3.1 METHODOLOGY
No.

Description of the affected environment is based on a literature review of published and
unpublished documents and maps, and personal communications with NPS staff at the
GCNRA and LMNRA. Information received includes the identification of navigation
issues associated with recreational boating on Lake Powell and Lake Mead, such as
navigation safety and safe boating densities. Low reservoir pool elevations identified in
the literature or through discussions with NPS as being of concern for reservoir boating
and navigation are discussed herein. Assessment of environmental consequences
associated with implementing the interim surplus criteria alternatives is based on river
system modeling and probability analyses of Lake Powell and Lake Mead pool
elevations exceeding identified thresholds.
Safe boating capacity is another aspect of boating navigation and safety. Safe boating is
one factor that can be used to assess the carrying capacity of a reservoir. To date, no
determination of carrying capacity (number of boats at one time) has been made for
either Lake Powell or Lake Mead. However, the NPS is currently developing a carrying
capacity approach for managing water-based recreation on Lake Mead that is based on

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the U.S. Forest Service Recreation Opportunity Spectrum system. Results of the NPS
study were not available for this analysis.
A safe boating density of nine acres per boat was established for the GCNRA (USBR,
1995b) at Lake Powell. The safe boating density could be used to assess the effects of
the interim surplus criteria alternatives on boating safety if daily boating levels for the
reservoir were available. However, there is no known information on the level of daily
or peak boating use, such as whether the current boating densities on the reservoirs have
approached or exceeded the safe boating density (as discussed below). Without
information on current reservoir boat densities, it is not known whether future
reductions in pool elevations at Lake Powell and Lake Mead would result in unsafe
boating conditions.
3.9.3.2 AFFECTED ENVIRONMENT
3.9.3.2.1 Lake Powell Boating Navigation and Safety
In 1986, the GCNRA developed an “Aids to Navigation Plan” for Lake Powell that
identified boating safety issues on the reservoir and low pool elevations that could
affect boating (NPS, 1986). The navigation system uses regulatory buoys and other
or
nteri 7
marking devices to warn boat operators of hazardous conditionsIassociated with
1
f the
subsurface obstructions or changes in subsurface conditions that 29, 20 hazardous for
pt. o er could be
e
safe passage. Placement of many of these n v. D devices b dependent on the lake
marking
em is
Natio d on Nov
elevation.
ajo

ive
Nav
d in 36804, arch there are several places that remain passable,
cit below 686 feet msl,
At pool elevationse
-1
although buoys are placed for safe navigation. At elevation 3626 feet msl and 3620 feet
o. 14
N
msl, there are two areas on the reservoir that are closed to commercial tour boats and
recreational boats, respectively, because of hazardous obstructions to navigation. One
of the areas is around Castle Rock, just east of the Wahweap Marina, and the other is
around Gregory Butte, which is about midway to Dangling Marina from Wahweap (as
shown on Map 3.9-1). At elevation 3626 feet msl commercial tour boats leaving the
Wahweap Marina heading up reservoir (east) must detour 8.5 miles around the southern
end of Antelope Island. At Gregory Butte, commercial tour boats must detour 4.5 miles
around Padre and Gregory Buttes (NPS, 1986). The added mileage and increased travel
time makes the more popular half-day trips of the area infeasible for commercial tour
boat operators. In addition, the added mileage may influence recreational boaters to
remain in the area of Wahweap Bay, which can result in congestion (Henderson, 2000).
In addition to buoys marking obstructions, the Aids to Navigation Plan also established
a marked travel corridor to guide boat travel on Lake Powell. This primary travel
corridor is the main channel of the old Colorado River bed and is marked with buoys
along the entire length of the reservoir. Except for the reservoir mouth, there are no
known pool elevations at which boat passage along this main travel corridor becomes
restricted and affects boating.

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Near the upstream end of the reservoir, where the San Juan River enters, a delta has
formed that can affect river boaters coming into Lake Powell at low pool elevations.
River boaters from the San Juan River paddle through Lake Powell to a location where
a boat transports them 20 to 25 miles (depending on the pick-up location) to the Hite
Marina. At low water surface elevations, the river boaters must travel further
downstream to reach a location that is accessible to the transport company’s boat.
Although this results in more miles to paddle to the takeout, there is usually enough
current in the river to carry the boats. For some boaters, the added mileage is an
opportunity to paddle additional rapids on the Colorado River in Cataract Canyon
(Hyde, 2000). For others, the additional mileage is seen as exposure to additional
navigational hazards, possibly requiring portaging of boats due to restricted channel
widths and subsurface conditions.
3.9.3.2.1.1 Lake Powell Safe Boating Capacity
Recreational boating is the most frequent type of boating activity on Lake Powell, with
an estimated 1.5 million boaters per year. One of the most popular activities at Lake
Powell is to take houseboats and motor boats for multiple day excursions to explore the
reservoir.
rior

Inte 17
f the at 9, 2time (i.e., safe
The number of boats that Lake Powell can safely accommodate 2 one 0
t. o
Dep mber
. Outdoor Recreation standard of nine
boating capacity) is based on a 1977 Bureau v
of
tion amount ove
surface acres per boat (USBR, ajo Na Thed on N of water storage in Lake Powell
1995b).
v
e
directly influences thein Na area rchiv reservoir and the number of boats that can
d surface 4, aof the
cite 1 86
safely be on the reservoir.6Table 3.9-7 lists median July Lake Powell surface areas for
baseline conditions 14 alternatives in the year 2016 and identifies the safe boating
No. and
capacity of the reservoir at those elevations, based on an assumed maximum safe
density of nine acres per boat. The surface area of Lake Powell is reduced by
approximately 9 to 10 percent for each 20-foot drop.

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Table 3.9-7
Lake Powell Safe Boating Capacity at Water Surface Elevations

Scenario

Median Elevation in
July of Year 15
(feet msl)

Water Surface Area
(acres)

Safe Boating
1
Capacity

Baseline Conditions

3665

134,600

14,956

Basin States Alternative

3664

134,100

14,900

Flood Control Alternative

3665

134,600

14,956

Six State Alternatives

3664

134.100

14,900

California Alternative

3660

130,800

14,533

Shortage Protection Alternative

3659

130,200

14,467

1

Number of boats, assuming safe density of 9 acres per boat.

At full pool for Lake Powell (3700 feet msl), the surface area is 160,782 acres. Using
the safe boating density of nine surface acres per boat, Lake Powell’s safe boating
capacity at full storage is approximately 17,865 boats. As pool elevation decreases, the
surface area available for boats also decreases. While safe reservoir boating carrying
ior
capacity is reduced at lower lake elevations, there may be additional shoreline camping
Inter 17
0
f the
available due to more exposed beaches. However, boating capacity,is more constrained
pt. o er 29 2
e
v. of
by safe boating densities than by the availabilityD camping sites on Lake Powell
mb
ation on Nove
(Combrink and Collins, 1992).ajo N
d

ive
Nav
d in 64, arch
3.9.3.2.2 Lake ite Boating Navigation and Safety
cMead 168
14No.
Similar to the navigation system on Lake Powell, regulatory buoys and other marking
devices are used on Lake Mead to warn boat operators of dangers, obstructions, and
changes in subsurface conditions in the main channel or side channels.

As with Lake Powell, the main channel of the old Colorado River bed forms the
primary travel corridor on Lake Mead and is marked along its entire length with buoys
for boating guidance. In addition, regulatory buoys are placed in areas where there may
be a danger for safe passage.
Excursions from Lake Mead into the Grand Canyon are a popular activity. Boats
entering the Grand Canyon usually launch at Pearce Ferry, South Cove or Temple Bar
(refer to Map 3.9-2). There are no developed facilities at South Cove or Pearce Ferry.
Points of interest in the Grand Canyon include Columbine Falls, Bat Cave, Spencer
Creek, and Separation Canyon. In addition to sightseeing being a popular activity,
many boaters include overnight camping stays on these excursions (USBR, 1995b).
The upper arms and inflow areas of Lake Mead are considered dangerous for navigation
due to shifting subsurface sediments. In the main channel of the reservoir, the Grand

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Wash Cliffs area is the beginning of dangerous navigation conditions, and no
houseboats are allowed beyond this point (NPS, undated).
Over the years, sediment has built up in the section of the reservoir between Grand
Wash and Pearce Ferry. When lake elevations drop below 1170 feet msl, the sediment
is exposed as mud flats and there is no well-defined river channel. As a result, the area
is too shallow for motor boats to navigate upstream and into the lower reaches of the
Grand Canyon. With fluctuating flows, even smaller crafts have a difficult time
accessing the area because of the shifting nature of the channel (USBR, 1995b). Based
on this information, 1170 feet msl is considered a threshold elevation for safe boating
navigation at Lake Mead.
While the area around Pearce Ferry is an issue for navigation at 1170 feet msl, it is also
inaccessible as a take out for whitewater boaters at elevation 1183 feet msl and boaters
must paddle an additional 16 miles to South Cove (Henderson, 2000). Paddling to
South Cove includes paddling through the section of reservoir between Pearce Ferry
and Grand Wash. (Refer to Section 3.9.2.2.3 for a description of the Pearce Ferry
facility, and Section 3.9.2.3.2 for an analysis of environmental consequences associated
with elevation 1183 feet msl.)

erior

In addition to the boating navigation issues summarized above, there are 17
e Int 0 swimmer
f thVegas,Bay and
safety issues at Lake Mead. At Gypsum Wash (between Las r 29 2
pt. o
. De withmbe
Government Wash), there are cliffs that iare popular ove recreationists for jumping into
nv
Nat o 1180 n N msl, the water is too shallow for
o
the lake. When lake elevations are belowed o feet
avaj rchiv
cliff jumping from thisn N
i location., Another jumping spot that was poplar during the late
4 a
cited levels were down is an area called “33 Hole.” This location is
1980’s when reservoir -1686
4
popular for cliff o. 1
N jumping when the lake elevation reaches 1165 feet msl. Cliff jumping
at both locations is discouraged by the NPS for safety reasons (Burke, 2000). Since the
activity is discouraged, the identified elevations were not considered as thresholds for
evaluation of effects.
3.9.3.2.3 Lake Mead Safe Boating Capacity
The LMNRA receives approximately ten million visitors annually. Of those that
participate in water-based recreation, most either swim, boat, fish, sailboard, use
paddlecraft, or scuba dive (USBR, 1996b). Since no boating capacity has been
established for Lake Mead, the safe boating density of nine acres per boat established
for Lake Powell was assumed; safe boating capacities were determined based on
reservoir elevation/surface area relationships. There is no daily or peak boating use
information available to establish the relationship between actual boating densities and
the safe boating capacity values shown below in Table 3.9-8. This table shows Lake
Mead surface area under the predicted pool elevations for baseline conditions and the
alternatives at the end of 2016, and identifies the safe boating capacity of the reservoir
based on an assumed maximum safe density of nine acres per boat.

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Table 3.9-8
Lake Mead Safe Boating Capacity at Water Surface Elevations
Scenario

Median Elevation at
End of Year 15
(feet msl)

Water Surface Area
(acres)

Safe Boating
1
Capacity

Baseline Conditions
Basin States Alternative
Flood Control Alternative
Six State Alternatives
California Alternative
Shortage Protection Alternative

1162
1143
1162
1145
1131
1130

120,200
108,100
120,200
109,400
102,100
101,700

13,356
12,011
13,356
12,156
11,344
11,300

1

Number of boats, assuming safe density of 9 acres per boat.

At full pool for Lake Mead, the operating surface area is 153,235 acres. Using the safe
boating density of nine surface acres per boat, Lake Mead’s safe boating capacity at full
storage is approximately 17,000 boats. As pool elevation decreases, the safe boating
capacity also decreases.
3.9.3.3 ENVIRONMENTAL CONSEQUENCES

rior

Boating navigation and safe boating densities on Lake Powelle Inte Mead are
and Lake 17
f th
20
. ofluctuate,9hazards, such as
dependent upon water surface elevations. As lakeept
levels
r2 ,
v. D
mbe
exposed rocks at lower pool elevations tor different navigational patterns at higher
a ion on Nove special buoys or markers may
N
elevations, may become evident. oAt low pool elevations,
vaj
Nanavigational ed
chiv hazards. In addition, signs may be placed in
be placed to warn boaters of
in
4, ar
ited for navigation.
c
areas deemed unsuitable1686
-

No.

14

Assessment of environmental consequences of the alternatives on boating navigation
and safety is based on river system model output, described in detail in Section 3.3.
The probability of effects under baseline conditions and the alternatives was determined
through identifying the probability of exceeding a representative “threshold” pool
elevation during the period of analysis. The selection of the threshold pool elevation is
based on the known boating navigation issues discussed in the Affected Environment
section above. The probabilities of the reservoirs remaining above the identified
threshold elevations are identified for baseline conditions and the interim surplus
criteria alternatives, and differences between probabilities under baseline conditions and
alternatives are compared.
In addition to navigation issues that occur at low pool elevations, the number of boats
that can safely be accommodated on the reservoir at one time (safe boating capacity) is
also a reservoir boating issue. As discussed previously, the lack of boating use data and
spatial modeling of the effects of the alternatives on shoreline conditions precludes a
quantitative or qualitative assessment of the impacts associated with the alternatives. In
general, as pool elevations change, so does the reservoir surface area and the number of
boats that can safely be accommodated on the reservoir. Therefore, the alternatives that

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result in the greatest potential for lower surface elevations would tend to increase the
likelihood of exceeding safe boating densities. Without current and projected boating
use levels for comparison to surface areas under the alternatives, it cannot be
determined whether the change in available surface area would result in an exceedance
of the calculated safe boating capacities shown in Tables 3.9-7 and 3.9-8, so
environmental consequences related to safe boating capacity are not analyzed further.
3.9.3.3.1 Lake Powell
For Lake Powell boating navigation, a reservoir pool elevation of 3626 feet msl was
identified as a representative threshold in Section 3.9.3.2.1. Figure 3.9-1 (presented
previously) shows elevation trends for baseline conditions and the alternatives over the
period of analysis.
In addition, as discussed in the section on shoreline facilities (Section 3.9.2.2.2),
elevation 3626 feet msl is also close to the elevation for a new proposed boat ramp at
Antelope Point, which will extend down to 3620. Using an assumption of six feet for
freeboard, the environmental consequences associated with elevation 3626 for
navigation are applicable to the future operability of the proposed ramp at Antelope
Point.
rior

Inte 1
f the 3626 feet7 under
Figure 3.9-6 depicts the probability of pool elevations .exceeding29, 20 msl
pt o
. De ember
v
baseline conditions and each of the alternatives. Table 3.9-9 presents a comparison of
tion n Nov
the probabilities associated withjo Na1 through 15, 16 through 28, and 29 through 49.
years
va
ed o
The probability decreasesNa 100chiv percent) during the analysis period under
in (from , ar to 65
cited all 8 the
baseline conditions and-16of64 alternatives. The probability is greatest for baseline
conditions andNo. Flood Control Alternative, and least for the California and Shortage
the 14

Protection Alternatives. The Six States and Basin States alternatives have probabilities
between the others.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-32

60%
2000

65%

70%

75%

80%

85%

90%

95%

100%

2005

2010

2015

2020

3.9-33

Year

2025

2030

2035

2040

2045

Flood Control Alternative

ior
Six States
Inter Alternative
e
17
of th California Alternative
t.
9, 20
p
2
v. De vember Shortage Protection Alternative
n
Natio d on No
jo
Nava archive
in
cited 16864,
o. 14
N

Basin States Alternative

Baseline Conditions

Figure 3.9-6
Lake Powell End of July Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to 3626 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

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Table 3.9-9
Probabilities of Lake Powell Elevation Exceeding 3626 feet in July
Projected Condition

Years 1 - 15

Range of Probability
Years 16 - 28
Years 29 - 49

Baseline Conditions

100%-86%

84%-72%

72%-65%

Basin States Alternative

100%-80%

80%-71%

71%-65%

Flood Control Alternative

100%-86%

84%-72%

73%-65%

Six States Alternative

100%-80%

80%-71%

71%-65%

California Alternative

100%-75%

73%-69%

71%-65%

Shortage Protection Alternative

100%-74%

74%-69%

71%-65%

3.9.3.3.1.1 Baseline Conditions
The probability of Lake Powell pool exceeding the safe boating navigation elevation of
3626 feet msl in July gradually decreases from 100 percent to 65 percent under baseline
conditions during the entire period of analysis. The probability decreases more slowly
under baseline conditions and the Flood Control Alternative than under the other
ior
Inter decreases from
alternatives. In the first 15 years of the analysis period, thethe
f probability 017
100 to 86 percent. From years 16 to 28, the probability o
pt. decreases 9, 2 84 to 72 percent.
r 2 from
De
mbe
For the remainder of the analysis period,on v.
the probability continues to decrease, declining
ati
Nove
from 72 to 65 percent.
ajo N ed on
v

in Na
rchiv
ited 6864, a
c
3.9.3.3.1.2 Basin States Alternative
-1
o. 14
N

The probability of Lake Powell pool elevation exceeding 3626 feet msl gradually
decreases from 100 percent to 65 percent under the Basin States Alternative during the
entire period of analysis. During the first 15 years, the probability declines more
rapidly than under baseline conditions, dropping from 100 to 80 percent. The
probability in year 15 is six percent less than under baseline conditions. Between years
16 and 28, the probability begins to converge with the probabilities of baseline and the
other alternatives, and ranges between 80 and 71 percent. During this period, the
probability is up to 7 percent less than under baseline conditions. For the remainder of
the analysis period, the probability is similar to baseline conditions and the other
alternatives, continuing to decline to a low of 65 percent.
3.9.3.3.1.3 Flood Control Alternative
For the Flood Control Alternative, the probability of Lake Powell pool elevation
exceeding 3626 feet msl is practically the same as for baseline conditions throughout
the analysis period. As shown in Figure 3.9-6, there are only three years in which the
probability is different (within one to two percent) from baseline conditions.

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3.9.3.3.1.4 Six States Alternative
The probability of Lake Powell elevation exceeding 3626 feet msl under the Six States
Alternative is identical to the probability under the Basin States Alternative in all but
four years, when there is a one percent difference.
3.9.3.3.1.5 California Alternative
The California Alternative results in the lowest probability of Lake Powell pool
elevation exceeding 3626 feet msl. The probability decreases from 100 to 75 percent in
the first 15 years of the analysis period. Between years 16 and 28, the probability
begins to converge with the probabilities under baseline and the other alternatives,
ranging between 73 and 69 percent. For the remainder of the analysis period, the
probability is similar to baseline conditions and the other alternatives, continuing to
decline to a low of 65 percent. During these three periods, the probability is up to 14
percent, 12 percent and 5 percent, respectively, below the probability under baseline
conditions.
3.9.3.3.1.6 Shortage Protection Alternative

ior

ter
For the Shortage Protection Alternative, the probability of Lake IPowell pool elevation
7
he n Alternative
exceeding 3626 feet msl is nearly the same as underpt. of t
the California9, 201
2
throughout the analysis period. The probabilityD up toember
v. ise
ion of theNov 12 percent less than under 16
baseline conditions during the first Nat
ajo 15 yearsd on analysis period. Between years
and 28, the probability n Navto convergee
begins
chiv with the probabilities under baseline
i
4, ar
ited alternatives, and is up to 11 percent less than under baseline
conditions and c other 686
the
-1
conditions. For the 14
o. remainder of the analysis period, the probability is within 5 percent
N
of baseline conditions.
3.9.3.3.2 Lake Mead
A reservoir pool elevation of 1170 feet msl was identified as the representative
threshold for boating navigation at Lake Mead, as described in Section 3.9.3.2.2.
Figure 3.9-7 depicts the probability of Lake Mead end-of-December pool elevations
exceeding 1170 feet msl for baseline conditions and the alternatives. Table 3.9-10
compares the probabilities associated with years 1 through 15, years 16-22, and years
23 through 49.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.9-35

0%
2000

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2005

2010

2015

2020

3.9-36

Year

2025

2030

2035

2040

2045

ior
Inter 17
e
20
of thShortage Protection Alternative
ept. ber 29,
D
m
n v.
atio on Nove
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N
California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

Figure 3.9-7
Lake Mead End of December Water Elevations
Comparison of Surplus Alternatives to Baseline Conditions
Percentage of Values Greater than or Equal to 1170 Feet

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Percent of Values Greater than or Equal to

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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Table 3.9-10
Probabilities of Lake Mead End-of-December Elevation Exceeding 1170 feet
Range of Probability
Projected Condition
Years 1 – 15

Years 16 - 22

Years 23 - 49

100%-45%

45%-38%

40%-34%

Basin States Alternative

99%-38%

40%-38%

40%-34%

Flood Control Alternative

100%-46%

47%-39%

42%-34%

Six States Alternative

100%-39%

40%-38%

40%-34%

California Alternative

80%-33%

40%-36%

40%-34%

Shortage Protection Alternative

80%-34%

40%-35%

40%-34%

Baseline Conditions

Under baseline conditions and the alternatives, the probability of Lake Mead pool
elevation exceeding 1170 feet msl declines during the interim period, then stabilizes for
the remainder of the period of analysis. The probability is greatest for baseline
ior
conditions and the Flood Control Alternative, and least for the California and Shortage
Inter 17
Protection Alternatives. The Basin States and Six States alternatives 20 probabilities
have
f the
pt. o er 29,
e
between the others.
b
v. D

n
em
Natio d on Nov
3.9.3.3.2.1 Baseline Conditionso
vaj
e
in Na 4, archiv
d
ite
6
The probabilitycof Lake 168 pool elevation exceeding the safe boating and navigation
- Mead
. 14msl at the end of the year declines from 100 to 34 percent under
No
elevation of 1170 feet
baseline conditions throughout the entire period of analysis. Probabilities decrease
more slowly under baseline conditions than under all alternatives except for Flood
Control. In the first 15 years of analysis, the probability declines from 100 to 45
percent. Between years 16 and 22, the probability continues to decline from 45 to 38
percent, as the alternatives converge with baseline conditions. For the remainder of the
analysis period, the probability under baseline conditions is similar to the alternatives,
ranging between 40 and 34 percent.
3.9.3.3.2.2 Basin States Alternative

The probability of Lake Mead pool elevation exceeding 1170 feet msl declines from 99
to 34 percent throughout the entire period of analysis for the Basin States Alternative.
As with most other alternatives, the decrease occurs during the interim period and
occurs more quickly than under baseline conditions. In the first 15 years of the analysis
period, the probability drops from 99 percent to 39 percent and is typically up to 13
percent less than under baseline conditions. Between years 16 and 22, the probability
stabilizes and converges with baseline conditions. The range of probability is from 40
to 38 percent, and is up to five percent less than under baseline conditions. For the

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remainder of the analysis period, the probability is within one percent of baseline
conditions, ranging between 40 and 34 percent.
3.9.3.3.2.3 Flood Control Alternative
The probability of Lake Mead pool elevation exceeding 1170 feet msl under the Flood
Control Alternative is typically up to two percent greater than under baseline
conditions. In the first 15 years of analysis, the probability decreases from 100 to 46
percent, and is within one percent of baseline conditions. Between years 16 and 22, the
probability continues to decline, ranging between 47 and 39 percent, and is typically
one percent greater than under baseline conditions. For the remainder of the analysis
period, the probability is up to 4 percent greater than baseline conditions, ranging
between 42 and 34 percent.
3.9.3.3.2.4 Six States Alternative
The effects of the Six States Alternative would be nearly the same as those for the Basin
States Alternative. In the first 15 years of the analysis period, the probability of Lake
Mead elevation exceeding 1170 feet msl is typically up to 11 percent less than under
baseline conditions. Between years 16 and 22, the probability stabilizesrand converges
rio of
with baseline conditions. The probability is typically within twonte
he I percent17baseline
2
of t
conditions. For the remainder of the analysis period, tthe probability is 0
ep . ber 29, within one
. D andempercent.
percent of baseline conditions, ranging between 40 v 34
ion v

No
Nat
vajo hived on
3.9.3.3.2.5 Californian Na
i Alternativerc
ited 6864, a
c
14- Mead pool elevation exceeding 1170 feet msl under the
The probability of.Lake 1
No

California Alternative is similar to that under the Shortage Protection Alternative and
less than under baseline conditions and the other alternatives. In the first 15 years, the
probability drops from 80 to 33 percent, then rises to 35 percent. The probability is up
to 31 percent less than under baseline conditions. Between years 16 and 22, the
probability rises slightly and converges with baseline conditions and the other
alternatives. The probability ranges from eight percent less than to the same as under
baseline conditions. For the remainder of the analysis period, the probability is within
one percent of baseline conditions.
3.9.3.3.2.6 Shortage Protection Alternative
The effects of the Shortage Protection Alternative are very similar to those described for
the California Alternative. The probability of Lake Mead pool elevation exceeding
1170 feet msl is generally within one percent of the probability under the California
Alternative throughout the period of analysis.

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3.9.4

CHAPTER 3

RIVER AND WHITEWATER BOATING

The Grand Canyon Protection Act directs the Secretary to operate Glen Canyon Dam in
accordance with the additional criteria and operating plans specified in Section 1804 of
the Act, and to exercise other authorities under existing law in such a manner as to
protect, mitigate adverse impacts to, and improve the values for which Grand Canyon
National Park and Glen Canyon National Recreation Area were established, including
but not limited to natural and cultural resources and visitor use.
The Glen Canyon Dam Adaptive Management Program (AMP) was established as a
Federal Advisory Committee to assist the Secretary in implementing the Grand Canyon
Protection Act. As discussed in Section 3.2.2, the AMP provides a process for
assessing the effects of current operations of Glen Canyon Dam on downstream
resources and using the results to develop recommendations for modifying operating
criteria and other resource management actions. While the interim surplus criteria
could have an influence on releases from Glen Canyon Dam, such releases will be
governed by the criteria in the Record of Decision, which was developed in full
consideration of both the safety and quality of recreational experiences in Glen and
Grand Canyons. A summary of the Glen Canyon Dam Record of Decision has been
included as Attachment D of this FEIS.
erior

nt
the I
f criteria 9, 2017 would
The only effect that implementation of the interimept. o
D surplus er 2 alternatives
have on whitewater boaters would be theon v.
possibilityovemb pool elevations in Lake
of lowered
ati
Nboaters onn NSan Juan River often end their trips
o
Powell and Lake Mead. Whitewater
e
avaj levels in d o the
at Lake Powell. Whilen N
i decreased archiv Lake Powell have effects on take out points
d
,
4
cite
in the Colorado and San1686
4- Juan Rivers, they also may expose additional rapids in Cataract
1
Canyon, which would expand whitewater rafting opportunities. Section 3.9.3.2.1
No.
discusses boaters entering Lake Powell.
Whitewater boaters on the Colorado River often end their trips in Lake Mead. Pearce
Ferry is the preferred Lake Mead take out for boaters, but it may not be accessible when
the reservoir pool elevation is below 1183 feet msl. An analysis of this elevation is
presented in Section 3.9.2.2. A take out is also available at Diamond Creek, upstream
of Lake Mead at the Hualapai Reservation. The Hualapai Tribe maintains the take out
area and road and charges a fee for take out. The Hualapai Tribe also conducts river
trips from Diamond Creek (on the Colorado River) to Pearce Ferry. This concession
may be affected if trips encounter changes in availability of the Pearce Ferry take out.
3.9.5

SPORT FISHING

This section considers potential effects of the interim surplus criteria alternatives on
recreational opportunities associated with sport fishing at Lake Powell, Lake Mead and
Lake Mohave (between Hoover and Davis Dam). Sport fishing in the Colorado River
between Glen Canyon Dam and Lake Mead will not be affected by the interim surplus
criteria action due to the protection afforded by the Adaptive Management Program (see

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Section 3.9.4). Fluctuations in flows between Hoover Dam and the SIB under the
alternatives would be within the historical operating range of the river. Therefore,
changes in flows under the alternatives would not affect recreation within these areas.
Adverse effects on sport fisheries from potential changes in water temperature below
Hoover Dam would not be expected, as discussed in Section 3.7.3.
3.9.5.1 METHODOLOGY
The discussion of the affected environment for reservoir fishing is based on a review of
published documents. Much of this information was derived from the following
sources: for Lake Powell, the Fish Management Plan, Glen Canyon National
Recreation Area (NPS, 1996); and for Lake Mead, the Desert Lake View Newspaper,
Fall/Winter 1999. In addition, creel information and angler fishing data has been
obtained from state agencies in Utah, Arizona, and Nevada responsible for managing
the fisheries resources at Lake Mead, Lake Powell, and Lake Mohave.
Assessment of potential impacts on sport fishing in Lake Powell, Lake Mead and Lake
Mohave is based on information presented in other sections of the document regarding
sport fishery populations (Section 3.7), reservoir shoreline facilities (Section 3.9.2) and
reservoir navigation (Section 3.9.3). There were no specific reservoir ipool elevation
or
Inter 7
thresholds related to sport fishing identified from the literature reviewed.1Catch rates
0
f the
for reservoir fishing are assumed to be directly related.to reservoir9, 2 discussed in
pt o er 2 habitat
e
D
mb
Section 3.7, Aquatic Resources. Fishingon v.
i satisfaction v assumed to be directly related
ataccesson theois e via shoreline facilities, andto
N water
the general recreation issues ofajo N
v boating ed to
boating navigation potential for , archi or reservoir detours due to low pool elevations.
in Na 4hazards v
ited 3.7, 6
As discussed incSection 168catch rates are not expected to be affected by fluctuations
4in pool elevations.. 1
No
3.9.5.2 AFFECTED ENVIRONMENT
3.9.5.2.1 Sport Fishing in Lake Powell
As discussed in Sections 3.7 and 3.8, native Colorado River species have not done well
in the reservoir environment. While some native species may spawn in the reservoir, it
is believed that the majority of young are eliminated by sport fish predators. The
predominant sport fishery in Lake Powell revolves around striped bass. The striped
bass depend on threadfin shad as a food source, so it is critical to maintain a balanced
shad population for the striped bass. The threadfin shad in Lake Powell are at the
northernmost portion of their range and are very sensitive to fluctuations in water
temperature. In addition to striped bass, Lake Powell supports largemouth and
smallmouth bass, walleye, channel catfish, bluegill, and black crappie. Lake Powell has
been stocked with fish almost annually, beginning in 1963 (NPS, 1996).

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Lake Powell is a popular fishing destination. Over three million people visit the
GCNRA annually, and those that fish spend a total of close to two million angler hours
in pursuit of a variety of sport fish.
Nearly all anglers fish by boat due to the cliff-like canyon walls of the reservoir. Shore
angling is rare. Annual angler use, based on boat fishing, is estimated to average
72,608 days. The majority of anglers (42 percent) come from Utah, followed by
Colorado (24 percent) and Arizona (23 percent). California and other states make up
the remaining 11 percent (Gustaveson, 2000).
Currently, the catch rate is 0.3 fish per hour, a number that has declined in recent years
due to angling pressure. Approximately one-half of the fish caught are harvested,
which results in an average annual harvest of 300,000 fish (NPS, 1996). Fishing catch
rates and harvest rates differ at Lake Powell due to changing public attitudes towards
catch and release. Most anglers release smallmouth bass and harvest striped bass. In
1997, 86 percent of the smallmouth bass caught were returned, compared to only 28
percent of the 396,000 striped bass caught (Gustaveson, 2000).
Most Lake Powell anglers seek a fishing opportunity and would rather catch any fish,
compared to a targeted individual species. However, when asked forraor
i species
In e anglers tend to
preference, most anglers prefer to catch black bass or striped bass. t Most17
f the 9, 0
target species they expect to catch most readily. (Gustaveson, 2000). 2
pt. o
e
r2

.D
be
on v Novem
atiincreasing biocontaminant concentration in
Recent studies have indicated a trend of d on
oN
avaj rchive
Ndam. Selenium has been found in plankton and in striped
aquatic organisms nearn
i the
,a
cited 1686 yet
bass. Although there have not 4 been any apparent negative impacts on striped bass
14reproduction, selenium can pose a health risk to anglers from consumption. If the
No.

presence of selenium continues, educating the anglers and performing risk assessment
studies may be necessary (NPS, 1996).
3.9.5.2.2 Sport Fishing in Lake Mead
Fishing is a favorite activity at Lake Mead. Largemouth bass, striped bass, channel
catfish, rainbow trout, bullhead catfish, sunfish, crappie, and bluegill can be found in
Lake Mead.
Lake Mead is famous for its striped bass, with an occasional catch weighing over 40
pounds, although weights of three to five pounds are more common. Angler survey
results from NDOW indicate that since 1984, striped bass have been the species most
sought after by anglers by a wide margin (62.7 percent) (NDOW, 2000). Fishing for
striped bass or largemouth bass is good throughout the entire lake, but panfish and
catfish are more prevalent in the upper Overton Arm.
The Nevada Division of Wildlife (NDOW) stocks rainbow trout from late December
through the spring months. The razorback sucker, a protected fish species, must be

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returned to the water immediately and carefully, if caught. Fishing is generally better in
the fall months of September, October and November. Larger fish are caught by deep
water trolling in spring from March through May.
To fish from shore, a valid license is required from the state where the fishing occurs.
If fishing from a boat or other flotation device, a use stamp from the other state is
required. Rainbow trout fishing also requires an additional stamp. Children under 14
are not required to have a license.
The NDOW conducts annual creel and angler use surveys of Nevada licensed anglers
(resident and non-resident). While Arizona licensed anglers also fish in Lake Mead, it
is estimated that roughly 80 percent of the fishing use on the reservoir is represented in
the NDOW surveys (Sjöberg, 2000). NDOW’s annual statewide angler questionnaire is
mailed out to 10 percent of all Nevada licensed anglers, resident and non-resident.
Table 3.9-11 presents data from 10 years of questionnaires.
Table 3.9-11
Nevada Division of Wildlife Annual Angler Questionnaire Results for Lake Mead
Fish per

ior Angler
Inter 17 Day
he
0
. of t
pt10.72 er 29, 2
44,444
476,543
940,608 De
21.16
1.97
.
b
ion v Novem
t
41,012
488,381 jo Na 934,807 n
11.91
22.79
1.91
o
va
ived
Na
ch
n
47,873 d i 792,883 , ar 1,532,481
16.56
32.01
1.93
cite 16864
4- 558,301
46,460 1
1,314,508
12.02
28.29
2.35
No.

Anglers

Angler
Days

Fish Harvest
(all species)

Days per
Angler

Fish per
Angler

1993

46,649

697,117

1,699,816

14.94

36.44

2.44

1994

45,507

648,928

1,710,412

14.26

37.59

2.64

1995

47,630

574,972

1,590,413

12.07

33.39

2.77

1996

42,715

554,625

1,410,440

12.98

33.02

2.54

1997

43,747

505,892

1,239,840

11.56

28.34

2.45

1998

43,831

612,551

1,568,676

13.98

35.79

2.56

Average

44,987

591,019

1,394,200

13.10

30.88

2.36

Year
1989
1990
1991
1992

Source: NDOW, Statewide Angler Questionnaire Database, 1989 through 1998, cover letter dated 5 October, 2000.

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The Arizona Department of Game and Fish estimated the Arizona licensed angler use
for Lake Mead (based on Nevada survey results) to be 118,422 days in 1995.
Combined with Nevada’s use estimate for the same year, there were 693,394 angler
days on Lake Mead in 1995 (83 percent from Nevada, and 17 percent from Arizona).
3.9.5.2.3 Sport Fishing in Lake Mohave
This section discusses sport fishing in Lake Mohave, below Hoover Dam. Table 3.9-12
shows the developed access sites and facilities at Lake Mohave.
Table 3.9-12
Lake Mohave Developed Recreation Facilities
Facilities

Willow Beach

Cottonwood Cove

Katherine

•

•

•

Lodging

N/A

•

•

Trailer Village (fee)

N/A

•

•

Campground

N/A

•

•

•

•

•

Ranger Station

erior
Food Service
•
• e Int
017
f th
Grocery/Gift Shop
pt. o • er 29, 2
•
. De
b
ion v Novem
Gasoline
•
a•t
on
jo N
Picnic Area
•
•
Nava archived
in
ited 6864, N/A
Shower (fee) c
•
1
. 14Trailer SewageNo
Dump
•
•
Marina

•
•
•
•
•
•

Boat Sewage Dump

•

•

•

Self-service laundry

N/A

•

•

•

•

•

N/A

•

•

Propane Service
Houseboat Rentals
Source: NPS, 1995.
indicates presence of improvement
•
N/A
indicates no improvement

In Lake Mohave there are largemouth bass, striped bass, channel catfish, rainbow trout,
bullhead catfish, sunfish, crappie and bluegill. Because Lake Mohave is within the
LMNRA, the same fishing rules and requirements described above for Lake Mead
apply to Lake Mohave. NDOW stocks rainbow trout in the lake from late December
through the spring months. The USFWS stocks rainbow trout throughout the year, with
concentrated stocking October through May.
Three protected species, including razorback sucker, Colorado squawfish, and bonytail
chub, are the last of the native Colorado River fish and can be found in Lake Mohave.

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When caught, these fish must be released. Fishing is open year round, but the best
fishing generally occurs in September, October and November. For deep water trolling,
March through May is best.
Fishing on Lake Mohave can be exceptional. Bass and trout often run three pounds,
with some trout weighing as much as 10 or more pounds. Anglers fish for big trout at
Willow Beach, while Cottonwood Cove and Katherine Landing offer both bass and
trout fishing. Within the last few years, striped bass fishing has become very popular.
The NDOW conducts annual creel surveys at Cottonwood Cove and Willow Beach. In
1998, angler use for Lake Mohave was estimated at 155,654 angler days, about the
same as in 1997. The 1998 lake-wide harvest was estimated at 414,954 fish. Of the
species caught, 80 percent were striped bass and 12 percent were rainbow trout. Other
species included largemouth bass, channel catfish, and sunfish.
3.9.5.3 ENVIRONMENTAL CONSEQUENCES
3.9.5.3.1 Sport Fishing in Lake Powell, Lake Mead and Lake Mohave
Reduced reservoir surface elevations could affect recreational reservoir fishing by
ior
decreasing the number of fishing days and angler satisfaction.eThe er
Int lower pool
7
th
elevations could cause temporary or permanent closure of relocation of01
pt. or er 29, 2 shoreline
e
b
facilities, thus requiring the boat angler to n v. D
another launch site, fish from
io either travel tom
ove
at day. on Nnavigational issues, such as the
the bank, or possibly forego fishingN
Also,
jo that
Nava arch ved
closure of areas of theireservoirs, could iincrease travel times to desired fishing locations
n
cited 16864,
and result in reduced angler satisfaction. Lower pool elevations may make some
shoreline fishingo. 14 inaccessible. In addition, as discussed in Section 3.9.3.2, as pool
N areas
elevations lower, the surface area available for boats and safe boat capacity decreases.
The boat angler may need to call ahead for reservoir conditions. Lake Mohave surface
elevations will not be affected by any of the alternatives.
No direct information on angler success rates or angler satisfaction in relationship to
reservoir pool elevations is available. Therefore, potential effects were determined
indirectly through consideration of potential effects on sport fishery production and
water access for boat and shore anglers. The effects of the alternatives on sports fishery
production are discussed in detail in Section 3.7.4. The effects on boating access,
including shoreline facilities that provide access to the water for boat angling and
navigational constraints on boating, are discussed in Sections 3.9.2 and 3.9.3.
As discussed in Section 3.7.4, Sport Fisheries, potential reductions in surface elevations
associated with the interim surplus criteria alternatives are not expected to affect sport
fishery composition or quantities within the reservoirs. As such, angler success rates at
Lake Powell and Lake Mead would not be reduced.

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3.9.6

CHAPTER 3

RECREATIONAL FACILITIES OPERATIONAL COSTS

In order to keep reservoir marinas, boat launching, public use beaches and shoreline
access operational, facility owners/operators and agencies providing utility connections
must respond to fluctuating pool elevations. This section focuses on the operational and
capital costs of keeping recreational facilities in operation as reservoir surface
elevations change.
Potential revenue effects from changes in recreation use are not considered. As
discussed above, it is not expected that baseline conditions or interim surplus criteria
would result in facility closures, as most facilities can be relocated to maintain operation
at lower reservoir elevations.
3.9.6.1 METHODOLOGY
Information in the affected environment section was compiled after review of available
published and unpublished sources and through personal communication with NPS
specialists. Available data do not cover all facilities. Furthermore, the analysis is
generally based on professional judgment, extrapolating from limited historical data.
However, the analysis provides a useful approximation of the order ofior
magnitude of
Inter 17
costs to recreational facilities that may be incurred under projections for each of the
f the 9, 20
alternatives.
pt. o
2
e

.D
ber
vem
ion vcosts, projections of the costs associated
Nat d
Using data associated with facility relocation on No
vajo hivthe river system modeling discussed in Section
with declines were made Na results of e
in using4, arc
itedpotential costs use model projections associated with the 50
6
c
3.3. Calculations of
-168
percent exceedence 14
. probability elevations for years 2002 through 2016. This
No
simplified methodology addresses multi-year changes in elevation, and does not
consider costs associated with facility adjustments to accommodate monthly
fluctuations.
3.9.6.2 AFFECTED ENVIRONMENT

The following sections discuss costs associated with relocation of reservoir marinas and
boat launching facilities at Lake Powell and Lake Mead. Many of the facilities at Lake
Powell and Lake Mead were constructed when the reservoirs were near their maximum
pool elevations of 3700 feet msl and 1210 feet msl, respectively.
3.9.6.2.1 Lake Powell
The costs of fluctuating pool elevations on Lake Powell marinas and boat-launching
facilities were calculated by Combrink and Collins (1992). The study calculated
operating costs for one-foot fluctuations (termed “normal adjustments”) and for
adjustments when the pool fluctuation exceeds 25 feet (termed “special adjustments”).
The normal adjustments are adjustments made within the range of regular operations
and are done routinely as water levels change during the year. Special adjustments

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include relocations of anchors and extensions of cables and utilities. The study found
that major capital investments would be needed; cost estimates were developed based
on a 50-foot decline in pool elevations.
Additional data for the Antelope Point Marina has been provided by the Navajo Nation
and National Park Service. Construction drawings have been prepared to allow
extension of the ramp from 3677 to 3620 feet msl, with a reported capital cost estimate
of approximately $500,000 (Bishop, Personal Communication, 2000). This cost has
been included in NPS planning for Antelope Point.
Table 3.9-13 presents the costs incurred per adjustment in the form that the data was
collected. In order to use the data to compare different alternatives, it has been
converted into a cost per foot of fluctuation. Data collected in 1989 has been updated to
2000 price levels.
Table 3.9-13
Costs Associated with Adjustments to Lake Powell Recreation Facilities
Cost per Adjustment
1

Adjustment Cost Category

Cost per Foot

ior
Inter 17
f the$1,721 0
Operating Cost for a Normal Adjustment
$1,275 t.
$1,721
p o er 29, 2
(based on one-foot fluctuation)
De
mb
n v.
o
ove
Operating Cost for a Special Adjustment Nati
$33,460
$45,171
$1,807
on N
ajo
(fluctuations exceeding 25 feet) av
ed
in N 4, archiv $2,000,000
Capital Cost for each 50-foot drop
$2,700,000
$54,000
cited 1686
4Total Cost per Foot. 1
$57,528
No
1989 Price
2
Level

Additional Capital Cost for drop below 3677
4
water surface elevation

2000 Price
3
Level

$500,000

1

. Operating costs are the cost of adjusting the existing facilities for fluctuations and consist of labor hours. Capital
costs consist of construction of ramp extensions, utility line extensions and relocations.
2
Combrink and Collins (1992).
3
Consumer Price Index-All Urban Consumers. 1989 average is 124.0. March 2000 is 167.8. Adjustment factor:
167.8/124.0 = 1.35
4
Capital cost to extend the toe of the existing Antelope Point Marina from 3677 to 3620 feet msl (Bishop, Personal
Communication, 2000).

Table 3.9-13 indicates there are costs associated with even minor changes in pool
elevations. However, the cost of capital improvements required to extend utilities and
access below the range of elevations that can be accommodated by existing
infrastructure is much larger than the operating costs incurred within the capacity of the
existing infrastructure.
It should be noted that many of the Lake Powell shoreline facilities were extended in
1992/93 to accommodate reduced Lake Powell surface elevation down to 3612 feet msl.
Due to these extensions, the actual costs of relocating facilities in the event of future

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Lake Powell surface elevation declines may be lower than those indicated in the
analysis.
3.9.6.2.2 Lake Mead
NPS provided information on costs associated with relocation of facilities at Lake
Mead. The operating levels range between full pool elevation (1210 feet msl) and
1180 feet msl. When Lake Mead declines to 1180 feet msl, adjustments need to be
made to the major facilities. Costs to make these adjustments for each of the major
facilities at year 2000 price levels range from $560,000 to $970,000. NPS has also
determined that additional incremental drops of 20 feet in elevation will incur additional
costs, ranging from $480,000 to $800,000 (Henderson, 2000).
Costs associated with fluctuating pool elevations are available for federally-owned
facilities at LMNRA from unpublished data assembled by the Resource Management
Office, Lake Mead NRA (Henderson, Burke and Vanderford, April 17 and 18, 2000).
In addition, Overton Beach Marina (letter dated March 29, 2000) and Lake Mead Resort
(letter dated April 11, 2000) provided information to Reclamation indicating the costs
associated with fluctuating reservoir elevations. Table 3.9-14 presents these costs.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
N
Cost per
jo Fluctuation
Increment
Nava archived
in
,
c ted 1 1686 of
Cost toiLMNRA facilities4 surface elevation occurrence below
$ 6,011,000
1180 feet.msl o 14
N
Table 3.9-14
Costs Incurred to Recreational Facilities from Lake Mead Pool Fluctuations
(Year 2000 Price Level)

Line
No.
1
2
3

5

Cost to Temple Bar Resort from a 10-foot drop

7

4

Cost to Overton Beach Marina Facilities from a fluctuation from 1150
3
feet msl to 1130 feet msl (20 feet)

6

3

Cost to Overton Beach Marina facilities from a fluctuation from 1212
3
feet msl to 1150 feet msl (62 feet)

5

2

Cost to Lake Mead Resort Marina from a 20-foot drop in elevation

4

1

Cost to LMNRA facilities at 1160 feet msl and at each additional
1
20-foot drop

Cost to Echo Bay Resort from a 20-foot drop from 1213 feet msl to
5
1193 feet msl

$ 5,080,000
2

4

$ 91,400
$ 60,000
$ 425,000
$ 12,500
$ 38,400

Unpublished data from Lake Mead NRA.
Letter dated April 11, 2000, from Lake Mead Resort to Reclamation. The letter quantifies cost for a drop from
current pool elevations. It also notes that a drop below 1150 would, in the NPS’s judgement, require
abandonment of the basin within which the resort is located.
Letter dated March 29, 2000, from Overton Beach Marina to Reclamation.
Letter dated March 27, 2000, from Temple Bar Resort. Midpoint of range ($10,000 to $15,000) is used. Letter
further notes that a drop below 1125 feet msl would require a complete relocation of the marina, including
buildings located on land.
Letter dated March 16, 2000, from Echo Bay Resort to Reclamation.

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3.9.6.3 ENVIRONMENTAL CONSEQUENCES
3.9.6.3.1 Lake Powell
As discussed in the methodology section, an estimate can be made of the cost impacts
of the alternatives on Lake Powell recreational facilities under some basic conditions.
Estimates in this section are for aggregate relocation costs associated with all identified
Lake Powell shoreline facilities.
Table 3.9-15 shows estimated incremental costs that would be incurred from Lake
Powell surface elevation decreases associated with the median elevation projections for
baseline conditions and each alternative from 2002 through 2016 (Figure 3.9-1 presents
these elevations graphically). These impacts are based on a cost of $57,528 per foot
change in elevation, developed based on the information shown in Table 3.9-12.
Table 3.9-15
Costs Associated with Potential Relocation of Lake Powell Recreational Facilities
1
Under Alternatives Compared to Baseline Conditions
(Year 2000 Price Level)

or
iIncremental Cost
Inter during 15-Year
017 3
f the
pt. o er 29, 2 Period
. De
b
Baseline Conditions
3665 n
0
--------io v Novem
at
ajo N3664 ed on
Basin States Alternative
1
$ 747,864
iv
Nav
d in 64, arch
$
0
Flood Control Alternative
3665
0
cite 168
4Six States Alternative 1
3664
1
$ 747,864
No.
Median Elevation
in Year 2016
2
(feet msl)

Elevation Below
Baseline
Conditions
(feet)

California Alternative

3660

5

$1,208,088

Shortage Protection Alternative

3659

6

$1,438,200

Alternative

1
2
3

Assumes pool elevation decreases constantly over time, following 50% probability of exceedence elevation.
Based on 50 percent probability of exceedence elevation projected from modeling on July 31 of each year.
Table 3.9-13. $57,528 per foot for each facility. No incremental cost is included for extending the ramp at the
Antelope Point Marina..

By 2050, the median elevation of all alternatives is within a two-foot range (3662.5 to
3664.6) and the difference in costs is small.
3.9.6.3.2 Lake Mead
As discussed in the methodology section, an estimate can be made of the cost impact of
the alternatives on Lake Mead recreational facilities using certain assumptions.
Table 3.9-16 shows estimated incremental costs that would be incurred from Lake
Mead surface elevation decreases associated with the median elevation projections for

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each alternative as compared to baseline conditions from 2002 through 2016 (Figure
3.9-4 presents the median elevations graphically).
Table 3.9-16
Costs Associated with Potential Relocation of Lake Mead Recreational Facilities
1
Under Alternatives Compared to Baseline Conditions
Elevation in
Year 2016
2
(feet msl)

Elevation Below
Baseline
Conditions

Incremental Cost
during 15-Year
Period

Baseline Conditions

1162

N/A

NA

Basin States Alternative

1143

19

$ 5,243,900

Flood Control Alternative

1162

0

0

Six States Alternative

1146

16

$ 5,243,900

California Alternative

1131

31

$ 10,348,900

4

Shortage Protection Alternative

1130

32

$ 10,773,900

5

Alternative

3

3

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited elevation4, all alternatives is the same (1110.6 feet msl), and
By 2050, the median -1686 under
4
no differencesNo. 1 would occur.
in cost
1
2

3
4
5

Assumes pool elevation decreases constantly over time, following 50% probability of exceedence elevation.
Based on 50 percent probability of exceedence elevation on December 31 of each year projected from river
system modeling.
Lines 2, 3, 4 and 6 from Table 3.9-14.
Two times Line 2, one times Line 3 and 4, and three times Line 6 from Table 3.9-14.
Two times Line 2, one times Lines 3, 4 and 5, and three times Line 6 from Table 3.9-14.

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3.10 ENERGY RESOURCES
3.10.1 INTRODUCTION
The analyses in this section consider two specific issues associated with energy
resources. The first issue considered is potential changes in hydropower production
from Hoover Dam and Glen Canyon Dam; the second is potential increases in energy
requirements of the Southern Nevada Water System (SNWS) Lake Mead intake, Navajo
Generating Station cooling water intake in Lake Powell and the City of Page potable
water intake in Lake Powell.
3.10.2 HYDROPOWER
This section discusses potential changes in power production that could occur as a result
of the interim surplus criteria under consideration. The analysis focuses on changes in
production from Glen Canyon Dam and Hoover Dam for each alternative compared to
baseline conditions.
3.10.2.1 METHODOLOGY

ior

ter
In order to determine the effects of the interim surplus criteria alternatives,7
he In detail1 the
of t
information produced from the river system modeling .described 29, 20 in Section 3.3
in
ept Canyon and Hoover
. D Glenember
has been used. This model simulates operation of
nv
Natio d interimv
powerplants under baseline conditions and theon No surplus criteria alternatives. The
vajo
output quantities of then Na that arehive
i model 4, arc important in determining the effects of the
d
alternatives on cite generation are:
power 1686
No.

14-

•

Annual average Lake Powell Elevation;

•

Annual average Glen Canyon Powerplant Energy Production;

•

Annual average Lake Mead Elevation;

•

Annual average Hoover Powerplant Energy Production;

•

Annual average Lake Mohave Elevation (constant at an elevation of 647 feet
msl throughout the period of analysis).

These quantities, derived from the model runs, are shown in Tables 1, 2, 5 and 7 in
Attachment P. In addition, powerplant capability curves for Glen Canyon and Hoover
powerplants showing powerplant capacity as a function of lake elevation (or net
effective head) are required to determine how the capacity varies for each alternative
throughout the study period. Powerplant capability curves used for the analysis are
presented in Tables 3 and 4 in Attachment P.

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Table 3 of Attachment P uses discharge multipliers to determine the maximum operable
capacity of the Glen Canyon Powerplant. The maximum water release of 25,000 cfs
(restricted except during power system emergencies) is divided by the discharge
multiplier to calculate the capacity. Table 4, for Hoover Powerplant, uses the
theoretical turbine curve data for heads from 560 feet to 590 feet. Below 560 feet of
head, a ratio of 2062/2074 has been applied to the turbine curve data to reflect recent
downratings of units A3, A4, and A8 as reported in a letter dated July 2000, from the
Area Manager of Reclamation to Western.
As used herein, powerplant capacity refers to the load that a generator or facility can
achieve at a given moment. Energy is a measure of electric capacity generated over
time. Comparing the projected amount of powerplant generating capacity and energy
production available under the various alternatives with baseline projections produces a
probabilistic measure of the effects of the alternatives on power production if the
assumptions contained in the forecasts covering water supply materialize.
The methodology for determination of the effects of the alternatives is to compare the
change in capacity and energy production, on an annual basis, between baseline
conditions and each alternative. Annual average generating capacity and energy
available from Glen Canyon and Hoover powerplants was determinedior the
using
Inter discussed in
reservoir elevation and energy output quantities from system modeling 017
f the
pt. o of 29, 2
Section 3.3, and the powerplant capability curves.eModelinger energy production is
b
v. D
based on aggregate turbine production curves. Annual em
ation on Nov average capacity and energy
jo N v alternatives are shown in Tables 5 and 7 in
production for baseline conditions and theed
Navaenergy production is also shown in Figures 3.10-1 and
chi
i
Attachment P. Annualn
4 r
ited average , a
6
c
3.10-2. Comparisons4-168annual average energy production associated with each
1 of the
. annual average energy production of baseline conditions are shown
alternative and the
No
in Tables 6 and 8 in Attachment P.
3.10.2.2 AFFECTED ENVIRONMENT
The energy resources that could be affected by changes in Colorado River operation are
Glen Canyon Powerplant and Hoover Powerplant electrical power output. The
reservoirs behind these facilities are operated to store Colorado River water for delivery
in the Lower Colorado River Basin below Glen Canyon Dam, and water to meet
delivery obligations to Arizona, California, Nevada and Mexico downstream of Hoover
Dam.
3.10.2.2.1 Factors of Power Production
In general, the two factors of a hydroelectric system, excluding machinery capability,
that are directly related to power production are the net effective head on the generating
units, and the quantity of water flowing through the turbines.

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The net effective head is the difference between the water surface elevations of the
forebay behind a dam and in the tailwater below the dam. The head determines the
maximum capacity, measured in MW, that is available from the powerplant. The
nameplate capacity of Glen Canyon Powerplant is 1296 MW. However, the maximum
operating capacity of Glen Canyon Powerplant generators is approximately 1200 MW
due to turbine restrictions (Western, 1998). Because the maximum allowable water
release has been limited to 25,000 cfs, the maximum operable capacity for Glen Canyon
is limited to 1048 MW, except during a power system emergency. The maximum
operating capacity of Hoover Powerplant is 2074 MW. The net effective head on the
powerplant is influenced by the reservoir surface elevations and operating strategies for
both the upstream and downstream reservoirs.
The quantity of water flowing through the turbines (water releases) determines the
amount of energy produced, measured in gigawatt-hours (GWh). The net energy
generated during fiscal year 1998 from Glen Canyon Powerplant and Hoover
Powerplant was 6626 GWh and 5768 GWh, respectively (Western, 1998 and
Reclamation, 2000).
The turbines at a powerplant are designed to produce maximum efficiency at a design
head. At design head, the plant can produce the maximum capacity and r most
te io the
Innetreffective head on
energy per acre-foot of water passing through the turbine.f Ase
th the
017
pt. o er 29, 2
the powerplant is reduced from design head because of reduced forebay (upstream
. De is reduced, the electrical capacity of
b
reservoir) elevation, the power outputation v
of the turbine ovem
N
jo N ved o and
the generator attached to the turbine is reduced,n the efficiency of the turbine is
i
Nava aas net effective head decreases until, below the
in
reduced. This reduction continues rch
ited 6864,
c
minimum elevation for-power generation, the turbines cannot be operated safely and
1
1 downstream water deliveries. Minimum power elevation
o.for 4
must be bypassed
N
generally occurs at a point where cavitation within the turbine causes extremely rough
operation, air may become entrained in the water, and/or vortices may appear in the
forebay.
3.10.2.2.2 Power Marketing and Customers
The effects of any surplus or deficit in power generation are incurred by the customers
to whom the power from Glen Canyon and Hoover powerplants is allocated. The
contracts for power from Glen Canyon Dam terminate in 2025. The contracts for power
from Hoover Dam terminate in 2017. The identity of the recipients of power from these
resources is not known for about two-thirds of the period of analysis for Hoover Dam
and about one-half of the period of analysis for Glen Canyon Dam. Therefore, an
analysis of the effects of the alternatives compared with those of baseline conditions
will consider the general effects in the overall areas served by the resources, although a
future group of power customers would be impacted similarly to current customers.
The states that would be affected by changes in energy and capacity at Glen Canyon
and Hoover powerplants are Arizona, California, Nevada, Utah, Wyoming, New

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Mexico and Colorado. These states make up the Rocky Mountain, Arizona-New
Mexico-Southern Nevada, and California-Mexico areas of the Western Systems
Coordinating Council (WSCC). Electrical energy produced in each of these areas is
derived from a variety of sources. The power from Glen Canyon Powerplant and
Hoover Powerplant contributes a small, but significant portion of the energy produced
in these areas. The total generation capability of the areas as of January 1, 1999, is
86,348 MW. The generation capability of each WSCC area is:
•

Rocky Mountain

10,584 MW

•

Arizona-New Mexico-Southern Nevada

22,272 MW

•

California-Mexico

53,492 MW

Glen Canyon and Hoover powerplants contribute approximately 3.6 percent of the total
generating capability of these three areas of WSCC (WSCC, 1999). The maximum
capacity available from Glen Canyon Powerplant at elevation 3700 feet msl has been
restricted to approximately 1200 MW. However, as stated above, the maximum
operable capacity at Glen Canyon Powerplant is limited to 1048 MW due to water
release restrictions, except during power system emergencies. Therefore, for the
or
nte i 7
IGlenrCanyon
purposes of this analysis, the operable capacities of Hooverthe
01
f and
powerplants are 2074 MW and 1048 MW, respectively,o a total9, 2
pt. for r 2 of 3122 MW.
e
D

v.
mbe
ation on Nove
3.10.2.3 ENVIRONMENTAL CONSEQUENCES
jo N
Nava archived
in
cited 16864,
The environmental consequences of a change in river operations that impacts power
14production can be .measured by the increase or decrease in capacity and energy available
No
from the powerplants. The power production under the alternatives is compared with
power production under baseline conditions to determine the incremental effects of each
alternative, using annual average modeled reservoir levels and downstream releases.
Reductions in capacity, energy, and generation ancillary services from Glen Canyon
and Hoover powerplants under baseline conditions would ultimately need to be replaced
by either types of generation. Additional incremental reductions under each alternative
would also ultimately need to be replaced.
The replacement of Glen Canyon and Hoover powerplant generation could be
accomplished through a number of different strategies. If capacity loss can be expected
for long periods of time, construction of new generation would likely occur. If capacity
loss is intermittent throughout the period of analysis, purchases from the short-term
market would be expected. If energy loss can be expected for a long period of time,
either construction of new generation or operation of higher-cost generation for longer
periods of time during the day would be expected. If energy loss is intermittent
throughout the period of analysis, replacement from the short-term market would be
anticipated.

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3.10.2.3.1 Baseline Conditions
3.10.2.3.1.1 Glen Canyon Dam
The annual average capacity and energy production at Glen Canyon Dam under
baseline projections are shown in Table 5 in Attachment P; the annual average energy
production is shown in Figure 3.10-1. The powerplant capacity begins at 1020 MW in
2002 and is reduced to 960 MW in 2016 because of reductions in lake elevation.
Subsequently, the capacity increases to 990 MW in 2041, then decreases to 975 MW in
2050. From 2002 through 2016, the greatest annual decrease in capacity is 13 MW
between 2012 and 2013. The annual reduction throughout the early years is from two to
six MW, representing less than a one percent decline in capacity from the powerplant
per year. The output varies cyclically between 2017 and 2050, with annual increases or
decreases in capacity of two to six MW.
Under baseline conditions, the energy available from Glen Canyon Dam averages 4532
GWh from 2002 through 2016, and 4086 GWh through the rest of the period of
analysis. Energy production increases the first year of the study. Thereafter, annual
reductions in energy production are generally less than 50 GWh per year through 2016.
Annual reductions in energy from 2017 through 2050 are generally less r
riothan 40 GWh.

Inte
f the 9, 2017
3.10.2.3.1.2 Hoover Dam
pt. o
. De ember 2
nv
Natio d Hooverv
The annual capacity and energy jproduction at on No Powerplant under baseline
va o
e
conditions are shown in Table 7 of Attachment P; the annual average energy production
in Na 4, archiv
d
cite 16 The
is shown in Figure 3.10-2. 86 powerplant capacity begins at 2062 MW in 2002 and is
reduced to 2033 o. 14 2016 because of reductions in lake elevation. Capacity
N MW in
decreases to 1865 MW in the year 2050. From 2002 through 2016, the greatest annual
decrease in capacity is nine MW. This reduction represents less than a one percent per
year decline in capacity from the powerplant through 2016. From 2017 through the
remainder of the period of analysis, the annual capacity reductions are generally less
than 10 MW.

The energy available from Hoover Powerplant averages 4685 GWh from 2002 through
2016, and 3903 GWh through the rest of the period of analysis. Energy production
increases during the first three years of the period of analysis, with annual reductions
from 2004 through 2016 of generally less than 50 GWh. Annual reductions in energy
from 2017 through 2050 are predominantly less than 60 GWh.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.10-5

3500
2000

3750

4000

4250

4500

4750

5000

5250

5500

Figure 3.10-1
Glen Canyon Powerplant
Annual Average Energy Production

2005

2010

2015

2020

3.10-6

Year

2025

2030

2035

2040

2045

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

Energy Production (GWh)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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3000
2000

3250

3500

3750

4000

4250

4500

4750

5000

5250

5500

Figure 3.10-2
Hoover Powerplant
Annual Average Energy Production

2005

2010

2015

2020

3.10-7

Year

2025

2030

2035

2040

2045

Shortage Protection Alternative

California Alternative

Six States Alternative

Flood Control Alternative

Basin States Alternative

Baseline Conditions

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

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Energy Production (GWh)

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

2050

CHAPTER 3

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3.10.2.3.1.3 Combined Capacity and Energy Reduction Under Baseline Conditions
The combined capacity reduction from Glen Canyon and Hoover powerplants through
2016 is 89 MW under baseline conditions. The combined energy production in 2016 is
403 GWh less than year 2002 energy production. In 2050, the capacity reduction is 242
MW less than 2002 levels, and the energy available is reduced 1807 GWh from year
2002 production. Under baseline conditions, power customers can expect a reduction in
production from present levels in the future. Because of the gradual withdrawal over
time, the deficit is expected to be replaced by short-term purchases made by either the
power customers or Western, at the power customer’s option, in accordance with
contract terms.
3.10.2.3.2 Basin States Alternative
3.10.2.3.2.1 Glen Canyon Dam
The average capacity available from Glen Canyon Powerplant under the Basin States
Alternative is shown in Table 5 of Attachment P. The powerplant capacity begins at
1014 MW in 2002 and is reduced to 960 MW in 2016. The capacity varies two to four
MW each year until 2050, at which time powerplant capacity is at 975 or
ri MW. The
average annual capacity available through the period of analysisInt987 MW.
is e
7
he

of t
, 201
ept. earlyer 29through 2016, and
The annual energy available averages 4527 GWh in theemb years
v. D
ation on Novenergy production in 2050 is
4209 GWh throughout the period of analysis. Annual
jo N
Nava archived
3875 GWh.
in
cited 16864,
1
3.10.2.3.2.2 Hoover 4No. Dam

The average capacity available from Hoover Powerplant is shown in Table 7 of
Attachment P. The powerplant capacity begins at 2061 MW in 2002 and is reduced to
1971 MW in 2016. The capacity either increases or decreases in consecutive years by
up to 44 MW, with the capacity in 2050 being 1865 MW. The average capacity
available throughout the period of analysis is 1935 MW.
The average annual energy available is 4701 GWh through 2016, and 4087 GWh
throughout the period of analysis. Annual energy production in 2050 is 3496 GWh.
3.10.2.3.3 Flood Control Alternative
3.10.2.3.3.1 Glen Canyon Dam
The average capacity and energy available from Glen Canyon Powerplant under the
Flood Control Alternative are shown in Table 5 of Attachment P. The powerplant
capacity begins at 1020 MW in 2002 and is reduced to 962 MW in 2016. The decline
continues to 975 MW in the year 2050. From 2002 through 2016, the greatest annual
decrease in capacity is 12 MW. This reduction represents less than a one percent

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average decline in powerplant capacity per year through 2016. The capacity either
increases or decreases in consecutive years through the remainder of the period of
analysis. Capacity changes from the period 2016 through 2050 are predominantly in the
two to six MW range each year, either increasing or decreasing.
Annual energy production from Glen Canyon averages 4532 GWh in the early years
through 2016 and averages 4223 GWh throughout the period of analysis. Annual
energy production in 2050 is 3875 GWh.
3.10.2.3.3.2 Hoover Dam
The annual capacity and energy available from Hoover Powerplant under the Flood
Control Alternative are shown in Table 7 of Attachment P. The powerplant capacity
begins at 2062 MW in 2002 and is reduced to 2033 MW in 2016. Powerplant capacity
continues on a declining trend, until the capacity reaches 1865 MW in 2050. The
greatest declines in the period from 2002 through 2016 are five and 13 MW, with the
annual decline in capacity being predominantly one to two MW.
Under the Flood Control Alternative, the annual energy available from Hoover
Powerplant averages 4686 GWh during the period 2002 through 2016.oThe average for
ri r
the period from 2017 through 2050 is 3908 GWh. The average Inte entire study
for the
f the 9, 2017
period is 4146 GWh.
pt. o
2
e

.D
ber
ion v Novem
3.10.2.3.4 Six States Alternative Nat
on
jo
Nava archived
in
3.10.2.3.4.1 Glened
Dam
cit Canyon864,
4-16
1
No.
The capacity available from Glen Canyon Powerplant under the Six States Alternative

begins at 1014 MW in 2002 and decreases to 960 MW in 2016. The capacity then
follows a generally increasing trend through 2043, after which annual reductions lead to
a capacity of 975 MW in 2050. The capacity available averages 980 MW throughout
the period of analysis. Annual changes of between two and five MW are predominant
in the Six States Alternative.
The annual energy production averages 4527 GWh through 2016, and 4211 GWh
throughout the period of analysis. Annual energy reductions throughout the period of
analysis are predominantly less than 50 GWh.
3.10.2.3.4.2 Hoover Dam
The capacity available from Hoover Powerplant under the Six States Alternative begins
at 2061 MW in 2002 and decreases to 2005 MW in 2016. The capacity then follows a
decreasing trend until the output reaches 1865 MW in 2050. The predominant annual
capacity reductions throughout the study period are less than 10 MW.

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The average annual energy production is 4698 GWh through 2016. The average annual
energy production throughout the period of analysis is 4091 GWh. Annual energy
production reductions in successive years are predominantly less than 50 GWh.
3.10.2.3.5 California Alternative
3.10.2.3.5.1 Glen Canyon Dam
The capacity available from Glen Canyon Powerplant under the California Alternative
begins at 1007 MW in year 2002, and is reduced to 958 MW in 2016. The capacity
follows a generally increasing trend from 2016 through the end of the period of
analysis. In 2050, the capacity is 975 MW. Annual changes in plant capacity are
generally between two and five megawatts.
Energy production at Glen Canyon averages 4516 GWh through 2016, and 4193 GWh
throughout the entire period of analysis. Annual changes in energy production are
generally less than 30 GWh.
3.10.2.3.5.2 Hoover Dam

r

The capacity available from Hoover Powerplant under the CaliforniarAlternative begins
te io
he In 2017 follows a
at 2061 MW in year 2002, and is reduced to 1907 MW inf2016. The capacity
o t
29,
ept.of the period of analysis. In
generally downward trend from 2016 through . D end mber
the
nv
e
2050, the capacity of Hoover is 1867 atio Annual ov
N MW. d on Nchanges in plant capacity are
ajo
v
generally less than 10 imegawatts. rchive
n Na

a
cited 16864,
Annual energy production at Hoover averages 4709 GWh through 2016, and 4016 GWh
14No. of analysis. Annual changes in energy production are
throughout the period
predominantly less than 20 GWh.
3.10.2.3.6 Shortage Protection Alternative
3.10.2.3.6.1 Glen Canyon Dam
The capacity available from Glen Canyon Powerplant under the Shortage Protection
Alternative begins at 1009 MW in 2002 and is reduced to 958 MW in the year 2016.
The capacity generally increases to 988 MW in the early 2040s, then is reduced to 975
MW in the year 2050. Annual capacity variations are generally from two to six
megawatts.
Energy production averages 4518 GWh through 2016, and 4193 GWh throughout the
entire study period. Annual energy production variations are generally less than 30
GWh.

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CHAPTER 3

3.10.2.3.6.2 Hoover Dam
The capacity available from Hoover Powerplant under the Shortage Protection
Alternative begins at 2061 MW in 2002 and is reduced to 1904 MW in 2016. The
capacity follows a generally decreasing trend from 2016 through 2050, when the
capacity reaches 1865 MW. Annual capacity reductions are predominantly in the two
to five megawatt range.
Annual energy production averages 4733 GWh from the beginning of the period of
analysis to 2016, and 4047 GWh throughout the entire period of analysis. Annual
variation throughout the period of analysis is generally less than 100 GWh.
3.10.2.4 COMPARISON OF ALTERNATIVES
As discussed above, the amounts of capacity and energy available as a result of each
alternative operating strategy vary on an annual basis. The important measurement of
the effects of each alternative is their comparison with the baseline conditions. As
indicated, the resources available from Glen Canyon and Hoover powerplants can be
expected to be reduced over time, due primarily to increased depletions in the Upper
Basin states. This effect is included in model runs for baseline conditions.
ior

Inter
hecapacity017 energy
of t
Table 3.10-1 summarizes the differences between hydropower 29, 2 and
ept. ber Values under the
.D
generation under each alternative and under baseline conditions.
m
ion v greater than
atslightly n Nove under baseline conditions.
N
Flood Control Alternative are typically
ajo
do
Values under the Californiaav Shortage e
in N and , archiv Protection Alternatives are the furthest from
cited 1 values
baseline conditions, while6864 under the Six States and Basin States alternatives are
14closer to baseline conditions.
No.
The capacity and energy differences (reductions) between each alternative and baseline
conditions would be replaced by power available from the market. The greatest singleyear difference in energy generation at Glen Canyon Powerplant under any of the
alternatives as compared to baseline conditions is 102 GWh, under the California and
Shortage Protection Alternatives (see Table 6 of Attachment P) or about 2.5 percent of
the modeled average annual generation of Glen Canyon. The effects of interim surplus
alternatives are greater at Hoover Powerplant. The greatest single-year difference in
annual energy generation under any of the alternatives as compared to baseline
conditions is 328 GWh under the California Alternative (see Table 8 of Attachment P),
or about eight percent of the modeled average annual energy generation. The average
annual generation during the period of analysis under the Preferred (Basin States)
Alternative is 0.8 percent (0.3 percent at Glen Canyon and 1.3 percent at Hoover) less
than under baseline conditions. The quantities of capacity needed to replace reductions,
while not significant when compared to the total capacity installed in the three WSCC
regions, may be significant to the entity losing the capacity.

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Table 3.10-1
1
Hydropower Capacity and Energy – Comparison of Alternatives to Baseline Conditions
2
(Difference between baseline conditions and each alternative )

Alternative

2002 – 2016
2017 – 2050
Average Annual
Average Annual
Capacity Energy Capacity Energy
(MW)
(GWh)
(MW)
(GWh)

2002 – 2050
Average Annual
Capacity Energy
(MW)
(GWh)

Glen Canyon Powerplant
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection
Alternative

-10
0
-10
-21
-21

-5
0
-5
-16
-14

-1
0
-1
-1
-1

-16
1
-15
-35
-36

-4
0
-4
-8
-7

-13
1
-12
-30
-29

Hoover Powerplant
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection
Alternative

-14
1
-11
-47
-45

15
0
13
24
20

-14
1
-12
-23
-20

-87
5
-80
-193
-147

-14
1
-12
-30
-28

-56
3
-51
-127
-96

ior
Inter 17
e
of th -103 , 20 -18
-24
10 ept. -15
r 29
D
1 n v. 0
1 b
1
m e 6
e
Natio d on Nov-13
-21
8
-95
-16
vajo -68 e 8
-24
-228
-38
in Na 4, archiv
ited 686
-66
6
-21
-183
-35
c
4-1
1
No.

Total
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection
Alternative
1

Appendix P, Tables 8 and 10 compare each alternative to baseline conditions.

2

-69
4
-63
-157
-125

Positive (negative) value indicates that cost is higher (lower) under the alternative.

At Glen Canyon, the greatest single-year difference in capacity compared to baseline
conditions is 36 MW under the Shortage Protection Alternative (see Table 6 of
Attachment P). This amount represents a decrease of 3.5 percent from baseline
conditions and approximately 0.3 percent of the installed capacity in the Rocky
Mountain Area. At Hoover, the greatest single-year difference in capacity compared to
baseline conditions is 137 MW under the California Alternative (see Table 8 of
Attachment P). This amount represents a decrease of 6.7 percent from baseline
conditions and about 0.2 percent of the installed capacity in the three-state marketing
area for Hoover.
Additional water releases resulting from four of the five alternatives (all but the Flood
Control Alternative) under consideration will increase the energy available from the
powerplants during the first two to seven years of the interim period. This can be
expected to reduce energy purchases by the customers from alternate, higher priced

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CHAPTER 3

resources. Future reductions in power production can be expected to necessitate
increased purchases of capacity to meet peak loads and reserves. Purchases of
replacement power by power customers would result in changes in costs and increased
exposure to market volatility.
3.10.3 SOUTHERN NEVADA WATER SYSTEM LAKE MEAD INTAKE
ENERGY REQUIREMENTS
This section discusses potential increases in operating costs of the SNWS Lake Mead
intakes that could occur as a result of implementation of the interim surplus criteria
alternatives. Increased pumping costs could occur if the alternatives cause lower Lake
Mead water surface elevations than baseline conditions.
3.10.3.1 METHODOLOGY
River system modeling, described in detail in Section 3.3, provided the average monthly
elevation of Lake Mead for each year during the study period for baseline conditions
and each of the alternatives. These elevations are shown in Table 2 of Attachment P.
Increases or decreases in net effective pumping head correspond to decreases or
increases in Lake Mead Surface elevations. The net effective pumping head differences
ior
Inter 1 2
between the baseline and the alternative strategies are also shown in Table7 of
f the
Attachment P. Using an estimate prepared by SNWA.(Johnson, 29, 20 incremental
pt o er 2000) for
e
b
pumping costs of $28,000 per year associated . D each foot of increased pumping
ion v with ovem
at is shown in Table 2 of Attachment P.
N
head, the increased cost of each jalternative d on
aoN

v
e
n Na , ar iv
d iNVIRONMENT ch
cite
3.10.3.2 AFFECTED E 16864
14No. through the SNWA, diverts most of its allocation of Colorado
The State of Nevada,

River water from Lake Mead through the SNWS into the Las Vegas Valley and
adjacent areas. The power-consuming features of this system are the pumping plants
from Lake Mead to the water treatment facility. The energy required to provide this lift
is a function of the net difference in elevation between the Lake Mead water surface and
the water treatment facility. Any increase in the net effective pumping head would
increase the amount of energy required to pump each acre-foot of water from Lake
Mead. The net effective pumping head will increase as the Lake Mead elevation falls.
Water users in Clark County, Nevada and possibly others would absorb increased costs
associated with water supply.
3.10.3.3 ENVIRONMENTAL CONSEQUENCES
The difference in net effective pumping head between each alternative and baseline
projections is used to determine the effects of each alternative on pumping cost. The
following analysis uses the estimate of $28,000 per year per foot increase in net
effective pumping head furnished in the aforementioned letter. Baseline pumping costs
were not calculated.

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CHAPTER 3

3.10.3.3.1 Baseline Conditions and Alternatives
Under baseline conditions, the average elevation of Lake Mead declines from 2002
through 2050. These results indicate that under baseline conditions and each of the
alternatives, SNWA can expect pumping costs to increase due to the increase in net
effective pumping head. Table 3.10-2 summarizes potential differences between
pumping costs under the alternatives and baseline conditions.
Table 3.10-2
Southern Nevada Water System Lake Mead Intake Energy Requirements
1
Average Annual Power Cost – Comparison of Alternatives to Baseline Conditions
(Differences between baseline conditions and each alternative)
Alternative
Basin States Alternative
Flood Control Alternative
Six States Alternative
California Alternative
Shortage Protection Alternative
1
2

2002-2016
$
229,395
$
-32,685
$
214,779
$
544,843
$
532,635

2017 - 2050
$
94,352
$
-21,025
$
88,027
$
205,652
$
170,314

2002 - 2050
$
135,691
$
-24,594
$
126,829
$
309,486
$
281,229

$28,000/per year per foot increase in net effective pumping head at year 2000 price level
Positive (negative) value indicates that cost is higher (lower) under the alternative.

ior
Inter results in
The Flood Control Alternative, when compared to baselinetconditions, 017
f he 9, 2
pt. ointo er system. The Basin
reduced costs for SNWA to pump Colorado Rivere
D water m its 2
n v. pumpingb increases of about
States and Six States alternatives resulttin averageNove cost
a io
ajo N ived on The California Alternative and the
$130,000 per year over the av period of analysis.
N entire
h
Shortage Protectiond in
Alternative , arc in average pumping cost increases of about
cite the 864 result of analysis.
$300,000 per year over-16 entire period
14
No.
3.10.4 INTAKE ENERGY REQUIREMENTS AT LAKE POWELL
This section discusses potential changes in pumping costs for two entities that pump
water from Lake Powell: the Navajo Generating Station which obtains cooling water
from Lake Powell, and the City of Page which obtains municipal water from Lake
Powell. Incremental differences in pumping costs are associated with differences in
modeled average Lake Powell surface elevations between baseline conditions and
alternatives.
3.10.4.1 METHODOLOGY
River system modeling, described in detail in Section 3.3, provided the average
elevation of Lake Powell for each year during the study period for baseline conditions
and for each of the alternatives. Increases or decreases in net effective pumping head
correspond with decreases or increases in Lake Powell surface elevations. Lake Powell
elevations and the net effective pumping head differences between baseline conditions
and the alternatives are shown in Table 1 of Attachment P. Estimates of the differences

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.10-14

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CHAPTER 3

in pumping costs were calculated using these changes in pumping head, as well as
estimates of annual water use, unit energy costs and pump efficiency.
The formula for calculating energy requirements (E) as a function of pump lift (H) is:
E = V * 1.024 * (H/e)
Where V is the volume of water pumped and e is pump efficiency.
3.10.4.2 AFFECTED ENVIRONMENT
The Navajo Generating Station is a 2250 MW, coal-powered plant jointly owned by
Reclamation, Salt River Project, Los Angeles Department of Water and Power, Arizona
Public Service Company, Nevada Power and Tucson Electric Power. The Salt River
Project (SRP) operates the plant. The SRP projects that water use will be
approximately 29,000 afy in the future. Power for the intake pumps is obtained from
auxiliary power units at the Generating Station at a cost of $0.0104 per kWh. Pump
efficiency is estimated by SRP at 75 percent. (Weeks, 2000)
The City of Page provides municipal water to approximately 7800 residents from Lake
erior produced at
Powell. The intake pump station is operated by Reclamation e Int power 7
using
01
f th dominated
the Glen Canyon Power Plant. Municipal water usept. Page is r 29, 2 by residential
in o
e
e
v. D A negligible amount of treated
use with substantial residential landscape irrigation. ovemb
ation for use at the dam. Presuming 275 gallons
N
water is delivered by the cityvajo N
to Reclamation on
v
Na wouldhbe ed
per day per resident, annual use , arc i approximately 2400 afy. An overall
in
ited for864pump station was used as a reasonable estimate. A cost
c
efficiency of 75 percent 16 the
4of $0.03 per kWh . 1 estimated as the cost of the electricity.
No was
3.10.4.3 ENVIRONMENTAL CONSEQUENCES
The difference in net effective pumping head between each alternative and baseline
projections was used to determine the effects of each alternative on pumping cost.
Baseline pumping costs were not calculated.
Under baseline projections, the average elevation of Lake Powell declines from
elevation 3685 feet msl in year 2002 to elevation 3661 feet msl in year 2050 (Appendix
P, Table 1). Table 3.10-3 compares the annual power costs of each alternative to
baseline conditions.
As Lake Powell water elevations are within hundredths of a foot for baseline conditions
and for the Flood Control Alternative, no change in pumping costs would occur. For all
other alternatives, Lake Powell water elevations average less than under baseline
conditions. Average pumping costs would be higher for both the Navajo Generating
Station (average increase of $808 per year over the period of analysis for the Basin
States Alternative) and for the Reclamation-operated raw water intake serving the City

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of Page. (Average increase of $193 per year over the period of analysis for the Basin
States Alternative).
Table 3.10-3
Intake Energy Requirements at Lake Powell
Average Annual Power Cost – Comparison of Alternatives to Baseline Conditions (Difference
between baseline conditions and each alternative)
Alternative

2002–2016

Navajo Generating Station Intake Energy Requirements
Basin States
$ 2,216
Flood Control
0
Six States
2,129
California
4,651
Shortage Protection
4,660
2
City of Page Municipal Water Supply
Basin States
$ 529
Flood Control
0
Six States
508
California
1,110
Shortage Protection
1,112
1
2

2017–2050
$ 186
0
172
303
312

$ 808
0
771
1,634
1,643

$

$ 193
0
184
390
392

44
0
41
72
74

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

E(kWh) = 1.024 * 29,000 * (H/0.75). Cost = E(kWh) * $ 0.0104
E(kWh) = 1.024 * 2,400 * (H/0.75). Cost = E(kWh) * $ 0.03
Estimates are annual averages for the indicated time periods.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.10-16

2002–2050

1

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3.11 AIR QUALITY
3.11.1 INTRODUCTION
Adoption of interim surplus criteria would not involve new construction or physical
activities that would result in air emissions within the area of potential effect considered
in this FEIS. Air quality effects discussed in this FEIS are limited to changes in fugitive
dust emissions that could result from changes in exposed reservoir shoreline as a result
of potential changes in Lake Mead and Lake Powell water surface elevations.
3.11.2 FUGITIVE DUST FROM EXPOSED SHORELINE
This air quality analysis provides an overview of ambient air quality in the project area,
as well as a qualitative review of the potential changes in fugitive dust emissions
associated with the project alternatives when compared to fugitive dust emissions that
may occur under baseline projections.
3.11.2.1

METHODOLOGY

Variations in fugitive dust emissions can result from changes in the arearof exposed
io
shoreline due to changes in water operating levels. The amountsnter
he I of fugitive dust and
17
generated per acre of exposed shoreline vary dependingof t soil 9, 20
pt. uponer 2 characteristics
e
other factors such as moisture content, wind v. D direction, and local topography. In
mb
ion speed, ovemission potential from exposed
at fugitive dust e
N
developing a methodology for ajo N
reviewing
d on
v Lake Mead, the following assumptions were made:
shoreline around Lakein Na andarchive
Powell

cited 16864,
14• The incremental changes in exposed shoreline area are related to incremental
No.

changes in water surface elevation as indicated by existing reservoir area elevation data. However, the true area of exposed shoreline terrain is also
affected by the slope of the terrain along the shoreline. To account for sloping
terrain, an average shoreline slope of 30 degrees and 45 degrees from horizontal
was assumed for Lake Mead and Lake Powell, respectively.

•

Incremental changes in fugitive dust emissions are directly proportional to the
changes in exposed shoreline area. Although some portions of exposed area
would have varying potential to generate fugitive dust, it is assumed that these
areas are distributed proportionally throughout the potential range of reservoir
surface elevations. Therefore, exposed areas were assumed to have a similar
emission rate for a given amount of exposed shoreline. It should be noted,
however, that estimated fugitive dust emissions were not calculated for this
analysis, and it is likely that certain areas of the exposed shoreline would be
expected to have higher emission rate factors than others. For example, delta
areas with high amounts of fine sediment deposit would be a more likely source
of fugitive dust generation than more compact or rocky soils at other exposed
locations.

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Based on these assumptions and using modeling results associated with projected
median surface elevations for Lake Powell and Lake Mead, potential changes in
shoreline exposure under baseline conditions and the interim surplus criteria alternatives
were identified.
3.11.2.2

AFFECTED ENVIRONMENT

Ambient conditions in the Las Vegas (Lake Mead) area are characterized by low annual
precipitation and generally light winds. Windrose data for the Las Vegas area for the
period 1992 through 1996 indicate the predominant wind directions to be from the west,
southwest, and south (i.e., away, rather than toward the Las Vegas metropolitan area)
throughout the year. Wind speeds are less than five miles per hour (mph) for
approximately 25 percent of the year and greater than 25 mph for less than one percent
of the year. The average wind speed is approximately nine mph. Ambient conditions
are similar for the Lake Powell area. Windrose data for Page, Arizona for the period
1992 through 1996 indicates there is no predominant wind direction. Rather, wind
direction is somewhat evenly distributed, with the exception of winds from the
southeast occurring less frequently. Wind speeds are less than five mph for more than
65 percent of the year and greater than 20 mph for less than one percent of the year.
The average wind speed is less than five mph.
erior

Int
f the 9, 2017 border.
Lake Mead is located on the Nevada (Clark County)/Arizona (Mohave County)
pt. o er 2
. De the federal Clean Air Act, in the
Air quality regulations, including implementation ofovemb
nv
at Clark n N
Ntheio d oCounty Air Pollution Control Division
Lake Mead area are administered by
vajo
ve
(Nevada) and the Arizona Departmenthi Environmental Quality (ADEQ). Air quality
in Na 4, arc of
d
cite 1686
regulations in the Lake-Powell area, which is located on the Arizona/Utah border, are
4
administered by o. 1
N the ADEQ and the Utah Department of Environmental Quality,
Division of Air Quality.

Pursuant to the federal Clean Air Act, as amended in 1990, the EPA has established
National Ambient Air Quality Standards (NAAQS) for a number of air pollutants,
which are considered harmful to public health or the environment. There are two types
of NAAQS, primary and secondary. Primary standards are designed to set limits for the
protection of public health, including the health of sensitive populations (receptors)
such as asthmatics, children and the elderly. Secondary standards are designed for the
protection of the public welfare, including visibility as well as damage to animals,
crops, vegetation and buildings. The EPA has established annual average and 24-hour
average NAAQS for particulate matter of less than 10 microns in diameter (PM10) and
particulate matter of less than 2.5 microns in diameter (PM2.5). Although the PM10
standards have been in effect for some time, the PM2.5 standards are more recent (1997).
Because development of baseline data for the latter is an ongoing effort and final
implementation of the PM2.5 standards may not occur for years, the discussion of
fugitive dust emissions focuses on PM10, which are more commonly understood and
encompass PM2.5 emissions in any event.

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Fugitive dust emissions such as those from exposed reservoir shorelines can contribute
to PM10 concentrations. To the extent that exposed shoreline is characterized by
relatively fine or light soils, fugitive dust emissions can result. However, given the
apparent nature of the reservoir shorelines (more gravel surface than soil) and the
relatively low average winds in the reservoir areas, soil materials from exposed
shoreline areas do not appear to result in significant fugitive dust emissions.
Another possible source of particulate emissions is from the deposition of dried plant
material left along the shoreline as the water level recedes. Given the nature of the
lakes’ bottom compositions and the relatively slow rate of reservoir water level
decreases, it is unlikely that this type of emissions source would be significant. The
lakes do not appear to contain high levels of algae, and the water levels are projected to
decline by a few feet per year (relative to baseline conditions). At this rate, algae or
other forms of plant matter would be likely to recede with the water rather than be
deposited along the shoreline.
Particulate emissions in the Lake Mead and Lake Powell areas do not appear to be a
significant problem. While some urban areas (including Las Vegas, North Las Vegas
and Henderson) within Clark County are not in attainment of the NAAQS for PM10, the
rest of the county, including Lake Mead, is in attainment of the standard. The portion
ior
Inter PM10 standard.
e
of Mohave County adjacent to Lake Mead is also in attainment of the 017
of th 29, 2
The northern central Arizona and southern UtahDept.
area, including Lake Powell, is also in
.
ber
attainment of the PM10 standard. This attainment status corresponds with windrose
ion v Novem
Nat
information for both areas (i.e., relatively ed on
vajo hiv low average wind speeds implying low wind
a
blown dust emissions in N 4, arc the relatively low levels of dust generated from
ited on average) and
c
86
human activities.
4-16

No.

1

Since both lake areas are used primarily for recreational purposes, there are limited
sensitive receptor population concentrations such as asthmatics, children or elderly
living in these areas.
3.11.2.3

ENVIRONMENTAL CONSEQUENCES

Based on modeled median surface elevations, baseline conditions will likely result in
decreased reservoir water levels and increases in exposed shoreline for both Lake Mead
and Lake Powell over the period of analysis. Median elevations under each of the
alternatives indicate a similar potential for increased shoreline exposure over time.
Tables 3.11-1 and 3.11-2 indicate Lake Mead and Lake Powell median surface
elevations identified through modeling (described in Section 3.3), as well as reservoir
surface area and exposed shoreline (based on shoreline slope estimates discussed in
Section 3.11.2.1) associated with these elevations. The greatest difference in exposed
shoreline between baseline conditions and each of the alternatives would generally
occur in the first half of the modeled period, as indicated under years 2016 and 2026 in
Tables 3.11 and 3.11-2. By year 2036, there are relatively minor variations in exposed

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shoreline associated with the median elevations under the alternatives as compared with
baseline projections.
Specifically, modeling results indicate an increased potential for fugitive dust emissions
under the Basin States, Six States, California and Shortage Protection alternatives when
compared with baseline projections throughout the initial, approximately 35 to 40 years
of the projections, with the greatest differences in shoreline exposure potential
occurring at or near the end of the interim period, in the year 2016. The Flood Control
Alternative would have a slightly decreased potential for fugitive dust emission over the
entire period of analysis when compared with baseline conditions.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.11-4

CHAPTER 3

1143

Basin States
Alternative

1125

1126

2026

1120

1121

2036

1

1111

1111

2050

108.1

120.2

2016

99.3

99.8

2026

97.4

97.6

2036

Reservoir Surface Area
(acres x1000)

93.6

93.6

2050

56.3

42.3

2016

66.4

65.9

2026

68.6

68.4

2036

Exposed Shoreline Area
(acres x1000)

2

1162

1128

1119

1111

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

2

1

Flood Control
Alternative

120.2

3.11-5

100.7

96.8

93.6

42.3

64.8

69.3

ior
Inter54.8 17 66.4 68.5
Six States
1145.5 1124.7
1120.4
1110.6
109.4
99.3
97.5
93.6
e
Alternative
of th 29, 20
t.
California
1131.2 1116.4
1117.6
1110.6
102.1
D p m 93.6 63.2 70.4 69.9
.95.9 e 96.3 ber
v
Alternative
ation on Nove
N 101.7
Shortage
1117.6
1110.6
96.3
93.6
63.7
69.7
69.9
1130.2 1117.9
vajo hived 96.5
Protection
Na
c
Alternative
ar
ed in 8
citsurface elevations. 64,
Based on modeled median reservoir
6
Area of exposed shoreline represents the area -1 would be exposed below the full pool elevation of Lake Mead for the various water surface elevations indicated,
14 that Lake Mead’s water surface area is 156,845 acres at water surface elevation of 1219.6 feet msl.
assuming an average shoreline slope of 30 degrees.
No.

1162

2016

Baseline
Conditions

Scenario

Surface Elevation
(feet msl)

73.0

73.0

73.0

73.0

73.0

73.0

2050

Table 3.11-1
Median Lake Mead Surface Elevation, Surface Area and Exposed Shoreline Area Under Baseline Conditions and Alternative Projections

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CHAPTER 3

3665

2016
3666

2026
3670

2036

1

3663

2050
134.6

2016
135.2

2026
138.0

2036

Reservoir Surface Area
(acres x1000)

132.6

2050
37.0

2016

36.2

2026

32.2

2036

Exposed Shoreline Area
(acres x1000)

2

3664

3666

3670

3663

134.1

135.2

138.0

132.6

37.7

36.2

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.11-6

assuming an average shoreline slope of 45 degrees. Lake Powell’s water surface area is 160,782 acres at water surface elevation of 3700 feet msl.

2

1

Basin States
Alternative

32.2

39.9

39.3

39.9

37.6

39.9

39.9

2050

ior
I er 17 36.2 32.2
Flood Control
3665
3666
3670
3665
134.6
135.2
138.0
134.2nt 37.0
e
Alternative
of th 29, 20
t.
Six States
3664
3666
3670
3663
134.1
135.2 ep 138.0
132.6
37.7
36.2
32.2
er
.D
Alternative
nv
emb
tio 131.6 ov
California
3660
3661
3670
3663 Na
jo 130.8ed on N 138.0 133.0 42.4 41.3 32.2
Alternative
Nava archiv
in
Shortage
3659
3661
4,
Protection
cited 36706863663 130.2 131.6 138.0 132.6 43.2 41.3 32.2
Alternative
-1
o. 14
Based on modeled median surface elevations.
N
Area of exposed shoreline represents the area that would be exposed below the full pool elevation of Lake Powell for the various water surface elevations indicated,

Baseline
Conditions

Scenario

Surface Elevation
(feet msl)

Table 3.11-2
Median Lake Powell Surface Elevation, Surface Area and Exposed Shoreline Area Under Baseline Conditions and Alternative Projections

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3.12 VISUAL RESOURCES
3.12.1 INTRODUCTION
This visual resource analysis addresses the scenic resources at Lake Mead and Lake
Powell. The analysis centers on the potential effects of increased shoreline exposure
that could result from implementation of the interim surplus criteria alternatives
considered in this document.
3.12.2 METHODOLOGY
The evaluation of the effects of the alternatives on the visual resources is based on an
assessment of the changes in reservoir shorelines caused by potential decreases in
reservoir water surface elevations. More precisely, the modeling indicates the increased
range of water level swings between the highs when reservoirs are full and the lows that
could occur when the Colorado River Basin natural runoff is low. The potential water
level lows have been described in Section 3.3 in terms of probability of occurrence,
based on operation model output. Consequently the visual effects are also presented in
terms of the probabilities of shoreline changes. Owing to the subjective nature of visual
qualities, this analysis is presented as a qualitative assessment of potential visual effects.
rior

Inte 17
f the of exposed shoreline
20
Changes in water elevation have differing effects on theo
ept. amount 29,
r
D
mb lake
depending on topography; the analysis tion v. changes in e levels to shoreline
relates the
a interpretedofrom existing topographic maps.
N ve
topography. The shoreline changesN
on
jo were
Nava archivedis derived from NPS documents and
The description of the iaffected environment
n
cited 16864,
commercial maps and literature describing scenery in the LMNRA and the GCNRA.
14No.
3.12.3 AFFECTED ENVIRONMENT

Both Lake Mead and Lake Powell are situated in desert areas of the Colorado River
Basin. While the desert vistas at the reservoir sites have a certain scenic attractiveness
of their own, the reservoirs have added a contrasting visual element that increases the
visual attractiveness of the areas, which are now dedicated as national recreation areas.
The uniqueness of the reservoirs with their contrasting surroundings has been widely
illustrated in travel and vacation literature, and has formed well known visual images
which help to draw multi-day visitors seeking water related recreation, and touring
motorists making day visits.
The reservoir water levels fluctuate both yearly and, to a lesser degree, seasonally.
During high runoff years reservoir inflows exceed the required releases and water is
stored, causing the water level to rise. During lower runoff years, when releases are
greater than inflows, water levels decline. The effects of water level changes on visual
qualities in the GCNRA and LMNRA depend greatly on the distance from which the
shoreline is viewed, and the type of topography forming the shoreline.

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3.12.3.1

CHAPTER 3

LAKE POWELL

Glen Canyon National Recreation Area is located in the Canyonlands area of the
Colorado Plateau. The plateau includes parts of Utah, Colorado, New Mexico, and
Arizona and is drained by the Colorado River and its many tributaries. The primary
attraction of the GCNRA is Lake Powell, a 186-mile-long reservoir on the Colorado
River that is formed by Glen Canyon Dam. Lake Powell extends along what was once
the Colorado River, through Glen Canyon and numerous side canyons to form more
than 1960 miles of reservoir shoreline. Recreationists enjoy exploring the endless side
channels and canyons of the reservoir by boat, often spending several days on the water
in houseboats or camping in remote areas. The combined qualities of visual
attractiveness and branching waterways create an attraction for many recreationists.
3.12.3.1.1

Landscape Character

In “carving” out the canyon landforms, the Colorado River and its tributaries formed a
labyrinthine pattern of deep twisted canyons whose towering walls exhibit the
geological history of the region. The sedimentary rock formations show multihued
sandstone and limestone layers and change color under differing sun angles occurring
during the day. Much of the land surface is bare rock with no soil cover. With little
erior
soil cover or moisture, there is minimal vegetation and littlehe Int
relief from the sun and the
017
ft
winds that blow across the vast plateau. Consequently, o terraced,plateau landscape
pt. the er 29 2
De
b
above the canyon walls displays the vaston v. of ovesandstone and limestone.
i expanse N red m
at
on
These red, orange and beige rocko N
j formations result in a dramatic landscape of towering
Nava ofaslickived and steep-sided canyons. Since the filling
rock spires, undulatingn
i plateaus , rch rock
4
cited decades ago, a dramatic contrast to this arid red rock
of Lake Powell several-1686
4
1
environment evolved in the form of the deep blue waters of Lake Powell, with their
No.
erratic patterns on the landscape likened to a blue lightening bolt in the red-orange
desert. Secluded side canyons support cottonwoods and poplars because of the shelter
from the wind provided by the canyon walls, and presence of water from tributaries.
Tamarisk, a non-native, invasive species, thrives along the lakeshore and in stream
bottoms, wherever it can find abundant water, forming a ring of green vegetation along
the less steep slopes of the reservoir. The reservoir and its protected surroundings in the
GCNRA form a valued recreation resource.
3.12.3.1.2

Sensitive Viewing Locations

The shoreline of Lake Powell and its adjacent landscape can be viewed from the
surrounding land at Glen Canyon Dam and its vicinity and from limited areas of the
canyon rim, notably the recreation-oriented area extending upstream of the lake from
the west end of the dam.
Access by boat permits the greatest amount and variety of scenic vistas; boaters
generally look forward to viewing canyon scenery during their visit to the area. The
vistas are relatively short in relation to the surface area of the lake, because of the

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sinuous shape of the lake, and the fact that much of the area lies in side canyons and
isolated basins along the meandering course of the former Colorado River corridor.
When Lake Powell water level declines, a white band of calcium carbonate appears on
rock surfaces where cliffs or rocky slopes form the reservoir rim. In areas where the
lakeshore consists of sand and gravel, an exposed beach belt emerges.
3.12.3.2
3.12.3.2.1

LAKE MEAD
Landscape Character

Lake Mead is situated in the northern part of the Mojave Desert and is surrounded by an
austere desert landscape. The lake extends about 66 miles upstream from Hoover Dam
and has about 695 miles of irregular shorelines with large bays and small coves.
Lake Mead is framed by low mountains with jagged rocky faces and profiles.
Intervening canyons and washes provide variation to the terrain, with the combination
presenting an interesting rugged type of scenery for many visitors. While the landscape
at midday is relatively subdued in terms of color, the contrast with the blue water of the
lake provides an appealing scenic area for visitors. Moreover, the contrasting “moods”
ior
of the surrounding desert visible between sunrise and sunset createter
In memorable scenic
f the 9, 2017
experiences.
pt. o
2

. De
ber
ion v Novem
3.12.3.2.2
Sensitive Viewing Locations on
Nat
vajo hived
in Na 4, corridor where Lake Mead is located consists of
rc
The portion of cited
the Colorado Rivera
86
-16
alternating narrow. rocky canyons and wide alluvial basins. Most of the lake and its
o 14
N
shoreline is visible only to people at widely scattered access points and from boats on

the lake. The major exceptions are the broad Hemenway Wash area on the west side of
the Boulder Basin of the lake, the Las Vegas Bay area on the west side of Boulder Basin
and Hoover Dam.
The Hemenway Wash area is a broad colluvial fan extending upslope from the lake to
the River Mountains on the west, with one contiguous area named Hemenway Valley
extending upslope southward and forming the northern part of Boulder City. At the
lake shore, the broad expanse of gradually sloping desert terrain has been developed
into a series of water-based recreation areas, consisting of, in a northward direction,
Hemenway boat launching area and water craft area (boating area with launching
ramps, docks, and shoreline areas designated for personal water craft use), the Boulder
Beach area, a largely unimproved gravel beach area for recreation including swimming,
windsurfing and sunbathing, with an adjacent overnight campground and a mobile
home community, and then the Lake Mead Marina, providing a boat berthing area,
restaurant and boat launching and docking facilities.
Westerly of the shoreline area, up the sloping desert terrain, is the boundary between the
LMNRA and the beginning of the Hemenway Valley section of Boulder City. This area

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has been extensively developed with condominiums and homes ranging in price up to
millions of dollars, with much of the area having been developed to take advantage of
lake vistas and views of the surrounding hills and desert landforms.
Las Vegas Bay to the north is a relatively narrow area of Lake Mead that is the initial
vista presented to people driving to the lake from the Las Vegas Valley. Vistas of the
lake are distant because the roads serving the area tend to be on benches above the lake
from which direct views of the shoreline are distant and intermittent. Hoover Dam is at
the south end of a narrow, steep-walled canyon, which is visible only from the dam and
the Arizona abutment and visitor parking areas.
When Lake Mead water level declines, two elements of the area’s vista are readily
visible. One element is the exposed beach belt around the perimeter of the reservoir
where the bottom consists of sand and gravel. The other element is a white band of
calcium carbonate on rock surfaces where cliffs or rocky slopes form the reservoir rim.
3.12.4 ENVIRONMENTAL CONSEQUENCES
3.12.4.1

BASELINE CONDITIONS

ior
Inter 17
f the 9, 0
pt. o conditions2would fluctuate
r2
D
The water surface elevation of Lake Powell undere
m e
n v. baseline b
e
between full level and lower level, with ithe amount ov duration of fluctuation
Nat o d on Nand
ajo Colorado River system. Moreover, the potential
v
depending on natural runoff in the rchive
in Na 4, a
dwould increase with the passage of time as the Upper Divisions
range of fluctuations
cite 1686
states increase their 14- of river water. An annual fluctuation of approximately 20 feet
use
No.
is projected, in step with the seasonal runoff cycle. Considering the annual fluctuation,
3.12.4.1.1

Lake Powell

the "average full" Lake Powell elevation for this analysis is considered to be an average
of approximately 3690 feet msl.
While the timing of major water level variations can not be predicted, nor the length of
time the water level would remain at the full level or at any other specific level, the
probable range of future baseline water levels has been estimated by the model. As
shown on Figure 3.3-6, the median water level decline would be 25 feet below the
average full level by the end of 15 years, after which the median level would remain at
or above that decline to 2050. There is also a 10 percent probability that the water level
would decline as much as 75 feet below the average full level by the end of 15 years,
and as much as 135 feet by 2050. However, as noted above, these lows would be
temporary, with a likelihood that the reservoir level would fluctuate up to full level
when high natural runoff conditions occur. The declines cited above represent the
average water levels under an annual 20-foot variation.
The visual consequences of such water level declines would affect boaters viewing two
types of shoreline. First, colorful sandstone canyon walls could show a white band of

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calcium carbonate deposit between the full water level and the lower water level, which
would detract from the visual contrast of rock and water. Second, the shoreline areas
consisting of sandy or gravelly desertscapes with their unique desert vegetation would
be altered by the interposition of a beach belt of sand and gravel between the full water
level and the lower water level. This could also alter the contrasting contact between
the blue water and the natural desert, and in some cases, distance boaters from the
natural terrain.
3.12.4.1.2

Lake Mead

As described in Section 3.3, the water surface elevation of Lake Mead under baseline
conditions would fluctuate between a full pool and increasingly lower lake levels, with
the amount and duration of fluctuations depending on natural runoff in the Colorado
River system. The potential range of fluctuations would increase with the passage of
time as the Upper Division states increase their use of river water. While the timing of
major water level variations can not be predicted, nor the length of time the water level
would remain at the full level or at any other specific level, the probable range of water
levels has been estimated by the model. An annual fluctuation of 10 to 20 feet is
projected, in step with the seasonal runoff cycle. Considering the annual fluctuation,
the "average full" Lake Mead elevation for this analysis is considered itorbe an average
ter o
of approximately 1215 feet msl.
he In
017
ft

,2
t. o
Dep mber 29
.level would decline 50 feet below the
As shown on Figure 3.3-13, the median iwater
nv
ve
Nat o d on Nothe median decline would continue
average full level by the end va15 years, after which
of jo
e
to 105 feet by 2050.dThere is alsoar10 percent probability that the median water level
in Na 4, a chiv
c te 1 120
would decline asi much-as686 feet below the average full level by the end of 15 years,
4
180 feet by the end 1 30 years, and then continue a gradual decline to 200 feet by 2050.
No. of
However, as noted above, these lows would be temporary, with the probability that the
level of Lake Mead level would fluctuate up to full level when high natural runoff
conditions occur.
The visual effect of such a decline perceived by the public would vary depending on the
proximity to the reservoir. Persons close to, or on, Lake Mead would perceive that the
water level had dropped greatly. However, along most of the alluvial shoreline the
exposed bottom would exhibit expanses of gravel. Boaters viewing cliff shorelines
would see a band of white calcium carbonate deposits that would probably detract from
their appreciation of the rock walls. Persons outside the LMNRA could notice a
reduction in reservoir level, depending on their distance from the lake and the degree of
visibility of the lake shore. However, beyond the alteration of the water shoreline and
the increased prominence of islands and outcrops in the lake, no degradation of the
viewshed would be anticipated.

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3.12.4.2
3.12.4.2.1

CHAPTER 3

BASIN STATES ALTERNATIVE
Lake Powell

Under this alternative the median water level would decline 25 feet below the average
full level by the end of 15 years, after which the median decline would be virtually the
same as under baseline conditions to 2050. There is also a 10 percent probability that
water level would temporarily decline as much as 85 feet below the average full level
by the end of 15 years, and continue a gradual decline to 140 feet by 2050. However, as
noted above, these lows would be temporary, with a likelihood that the reservoir level
would fluctuate up to full level when high natural runoff conditions occur. The declines
cited above represent the average water levels under an annual 20-foot variation.
The visual consequences would involve the same scenic changes described above for
baseline conditions.
3.12.4.2.2

Lake Mead

Under this alternative the median water level would decline 70 feet below the average
full level by the end of 15 years, after which the median decline would reach 105 feet
ior
by 2050. There is also a 10 percent probability that water level would temporarily
Inter 17
he
decline as much as 135 feet below the average full levelof tthe end of20 years, and 205
pt. by er 29, 15
e
feet by the end of 30 years and during the n v. D periodb 2050. However, as noted
ioremainingovem tothe reservoir level would
Na d likelihood that
above, these lows would be temporary,twith aon N
vajo natural runoff conditions occur.
fluctuate up to full level when high rchive
in Na

a
cited 16864,
14The visual consequences would involve the same scenic changes described above for
No.
baseline conditions.
3.12.4.3
3.12.4.3.1

FLOOD CONTROL ALTERNATIVE
Lake Powell

Under this alternative the Lake Powell water levels would be virtually the same as
under baseline conditions. The visual consequences would involve the same scenic
changes described above for baseline conditions.
3.12.4.3.2

Lake Mead

Under this alternative Lake Mead water levels would be virtually the same as under
baseline conditions. The visual consequences would involve the same scenic changes
described above for baseline conditions.

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3.12.4.4.1

CHAPTER 3

SIX STATES ALTERNATIVE
Lake Powell

Under this alternative the median water level would decline 25 feet below the average
full level by the end of 15 years, after which the median decline would be virtually the
same as under baseline conditions to 2050. There is also a 10 percent probability that
water level would temporarily decline as much as 85 feet below the average full level
by the end of 15 years, and continue a gradual decline to 140 feet by 2050. However, as
noted above, these lows would be temporary, with a likelihood that the reservoir level
would fluctuate up to full level when high natural runoff conditions occur. The declines
cited above represent the average water levels under an annual 20-foot variation.
The visual consequences would involve the same scenic changes described above for
baseline conditions.
3.12.4.4.2

Lake Mead

Under this alternative the median water level would decline 70 feet below the average
full level by the end of 15 years, after which the median decline would reach 105 feet
ior
by 2050. There is also a 10 percent probability that water level would temporarily
Inter 17
he
decline as much as 130 feet below the average full levelof tthe end of20 years, and 205
pt. by er 29, 15
e
feet by the end of 30 years and during the n v. D periodb 2050. However, as noted
ioremainingovem tothe reservoir level would
Na d likelihood that
above, these lows would be temporary,twith aon N
vajo natural runoff conditions occur. The visual
fluctuate up to full level when high rchive
in Na
a
itedinvolve 64,same scenic changes described above for baseline
c
consequences would
168 the
conditions. No. 14
3.12.4.5
3.12.4.5.1

CALIFORNIA ALTERNATIVE
Lake Powell

Under this alternative the median water level would decline 30 feet below the average
full level by the end of 15 years, after which the median decline would be virtually the
same as under baseline conditions. There is also a 10 percent probability that the water
level would decline as much as 95 feet below the average full level by the end of 15
years, and continue a gradual decline to 140 feet by 2050. However, as noted above,
these lows would be temporary, with a likelihood that the reservoir level would
fluctuate up to full level when high natural runoff conditions occur. The declines cited
above represent the average water levels under an annual 20-foot variation.
The visual consequences would involve the same scenic changes described above for
baseline conditions.

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CHAPTER 3

Lake Mead

Under this alternative the median water level would decline 85 feet below the average
full level by the end of 15 years, after which the median decline would reach 105 feet
by 2050. There is also a 10 percent probability that water level would temporarily
decline as much as 145 feet below the average full level by the end of 15 years, and 210
feet by the end of 30 years and during the remaining period to 2050. However, as noted
above, these lows would be temporary, with a likelihood that the reservoir level would
fluctuate up to full level when high natural runoff conditions occur.
The visual consequences would involve the same scenic changes described above for
baseline conditions.
3.12.4.6
3.12.4.6.1

SHORTAGE PROTECTION ALTERNATIVE
Lake Powell

Under this alternative the median water level would decline 30 feet below the average
full level by the end of 15 years, after which the median decline would be virtually the
same as under baseline conditions to 2050. There is also a 10 percent probability that
ior
the water level would decline as much as 95 feet below the averageer level by the end
Int full 17
the
of 15 years, and continue a gradual decline to 140 feet.byf2050. 29, 20 as noted
pt o er However,
e
b
above, these lows would be temporary lows, v. D a likelihood that the reservoir level
ion with Novem
at natural runoff conditions occur. The declines
would fluctuate up to full level when high
ajo N
d on
cited above represent the Nav waterilevels under an annual 20-foot variation.
average rch ve
in

a
cited 16864,
14The visual consequences would involve the same scenic changes described above for
No.
baseline conditions.
3.12.4.6.2

Lake Mead

Under this alternative the median water level would decline 85 feet below the average
full level by the end of 15 years, after which the median decline would reach 105 feet
by 2050. There is also a 10 percent probability that the water level would temporarily
decline as much as 140 feet below the average full level by the end of 15 years, and 210
feet by the end of 30 years and during the remaining period to 2050. However, as noted
above, these lows would be temporary, with a likelihood that the reservoir level would
fluctuate up to full level when high natural runoff conditions occur.
The visual consequences would involve the same scenic changes described above for
baseline conditions.

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3.13 CULTURAL RESOURCES
3.13.1 INTRODUCTION
Cultural resources include prehistoric and historic districts, sites, buildings, structures,
objects and landscapes. Historic properties are cultural resources that meet one or more
of the Secretary’s criteria of significance found at 36 CFR 60.4 and are listed on, or
have been found eligible for inclusion, in the National Register of Historic Places
(NRHP). The term also includes sites of traditional religious and cultural significance
to an Indian Tribe that meet one or more of the NRHP criteria – traditional cultural
properties. Section 106 of the National Historic Preservation Act (NHPA) of 1966, as
amended, requires all federal agencies to take into account the effects of their actions on
historic properties.
3.13.2 APPROACH TO ANALYSIS
The first step in the Section 106 process, as set forth at 36 CFR 800.3(a), is for the
Agency Official to determine if a proposed action meets the definition of an
undertaking. An “undertaking” is defined at 36 CFR 800.16(y) as “a project, activity,
or program funded in whole or in part under the direct or indirect jurisdiction of a
ior
Inter agency; those
federal agency, including those carried out by or on behalf the federal 17
0
f of a
carried out with federal financial assistance; thoseept. o a federal 2
requiring r 29, permit, license or
v. D
mbe
approval; and those subject to State or local regulation administered pursuant to a
ation The Nove has the authority to declare
jo agency.” on Secretary
delegation or approval by a federal N
ved
Nava artheiLROC developed pursuant to the Colorado
surplus conditionsed inreference to ch
with
,
4
cit
River Basin Project Act,1686 make surplus determinations during the AOP
4- and to
1
development process. Using the existing LROC and AOP process, the Secretary has
No.
declared the existence of surplus conditions every year since 1996 and could continue to
do so in the absence of interim criteria. Reclamation has determined development and
implementation of interim surplus criteria for use in conjunction with the LROC and
AOP process has the potential to temporarily change the way in which surplus is
determined for the period 2000-2015. Development and implementation of interim
surplus criteria can thus be construed as a temporary change in an ongoing activity that
is part of an existing program, the latter being the delivery of Colorado River water.
Thus, it meets the definition of an undertaking for the purposes of complying with
Section 106 of the NHPA.
The second step in the Section 106 process is to determine if the undertaking has the
potential to cause effects to historic properties. If an undertaking “does not have the
potential to cause effects on historic properties,” pursuant to 36 CFR 800.3(a)(1), the
Agency Official has no further obligations under Section 106. Effect is defined at
36 CFR 800.16(i) as “alteration to the characteristics of a historic property qualifying it
for inclusion in or eligibility for the National Register.” Reclamation has determined
development of interim surplus criteria is an undertaking, but one without potential to

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affect historic properties. Reclamation’s rationale for this determination is outlined
below.
3.13.3 AFFECTED ENVIRONMENT
The term area of potential effects (APE) is defined at 36 CFR 800.16(d) as “the
geographic area or areas within which an undertaking may directly or indirectly cause
changes in the character or use of historic properties, if any such properties exist.” This
section goes on to state “the area of potential effects is influenced by the scale and
nature of an undertaking and may be different for different kinds of effects cause (sic)
by the undertaking.” For the purposes of evaluating the potential for development and
implementation of interim surplus criteria to affect historic properties, the APE has been
differentially defined for Lake Powell, Lake Mead, the Grand Canyon, and the
reservoirs and river corridor from below Hoover Dam to the SIB. This is to address the
effects of changes in lake elevations and mean monthly flow rates predicted by the
hydrological modeling runs presented earlier in this EIS, and other factors. The APE
definitions used in this analysis are as follows:
Lake Powell: That area around the margin of the lake extending from the historic
maximum pool elevation of 3708 feet msl, to the 3595-foot contour. rThe 3595-foot
e ior
contour has been selected as the low elevation cutoff point,the Int
as hydrological modeling
017
f
runs indicate there is a 10 percent probability the surface elevation9, 2 lake could
pt. o er 2 of the
De Alternative.
b
drop to this level by 2016 for the Shortagen v.
io Protection vem
t
o

a
N
aj N
vtheolakehived on
Lake Mead: That area iaround
n Na
arc margin extending from its historic high water
ited feet864, The 1083-foot contour has been selected as the low
level of 1225.5c 1083-16 msl.
to
1
elevation cutoff point4 this represents the minimum pool level necessary for continued
No. as
power generation. The maximum flood pool elevation is 1229 feet msl.

Colorado River through the Grand Canyon: As discussed in Section 1.4.2, the Glen
Canyon EIS analyzes the effects of operation of Glen Canyon Dam on downstream
resources of the Grand Canyon, including cultural resources. The Record of Decision
(ROD) for this EIS provides for monitoring and management of affected cultural
resources. Section 106 compliance for existing operations and implementation of
surplus criteria are and will be subject to the Cultural Resources Programmatic
Agreement prepared with respect to the operation of Glen Canyon Dam. Thus it will
not be considered further in this analysis.
Colorado River from Hoover Dam to SIB: Downstream from Hoover Dam, the
Colorado River flows through a relatively narrow valley along which are located Lake
Mohave and Davis Dam, Lake Havasu and Parker Dam, and a series of smaller dams
that serve to impound and divert water for specific purposes. As indicated in Section
3.3.4, although Lake Mohave and Lake Havasu are located within the overall APE of
the current action, implementation of interim surplus criteria will have no effect on the
surface elevations or operation of these reservoirs. As a consequence, they are not

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considered further in this analysis. Below Davis and Parker dams, the river is fringed
by riparian vegetation and marshy backwaters, and a series of levees serve to contain its
flow. Because under all but the most exceptional circumstances (e.g., a catastrophic
flood event, levee failure, etc.), the flow of the Colorado River is expected to be
contained within its channel and the levees, and the APE for free-flowing stretches is
considered to be the river channel and that area of the floodplain lying within the levees.
3.13.4 ENVIRONMENTAL CONSEQUENCES
The No Action and each of the action alternatives could result in changes in the surface
elevations of Lake Powell and Lake Mead and changes in release patterns and flow of
the Colorado River below Hoover Dam. These changes could result in changes in
erosional and/or depositional processes that could affect historic properties, were such
properties present. However, Reclamation considers the probability for the existence of
cultural resources retaining qualities that would qualify them for listing on the NRHP
within the interim surplus criteria APEs, as defined above, to be extremely low.
Although Hoover and Glen Canyon dams were constructed prior to passage of the
NHPA in 1966, attempts were made to locate and salvage information from significant
prehistoric and historic archaeological sites prior to inundation by Lake Mead and Lake
erior
Powell. As a result of these efforts, numerous kinds of siteshe Int masonry
including 17
20
of t
structures, wattle and daub roomblocks, rockshelters,tlithic and ceramic scatters, trails,
ep . ber 29,
D
m
shrines, quarry locations, salt mines, andon v. towns, mills, roads, etc., are known to
historic
atilakes.on Nove
N
be submerged beneath the waterso the ed
vaj of

iv
Na
arch
d in
itecondition 64,the No Action Alternative, impacts that are likely to
c
Under the baseline
-168 for
. 14inundated by the reservoirs can be expected to vary in kind and
have occurred No
to sites

degree, depending on a number of factors including the type of site, slope, the substrate
on which the site is located, the site’s elevation with respect to historic operation of the
reservoir, the number of times a site has been inundated, exposed and re-inundated, etc.
In areas where the lake margins make contact with unconsolidated sediments (i.e.,
alluvial fans, fluvial deposits, etc.), wave action and rising and falling water levels can
cause cutting and bench formation, exposure and removal of finer-grained sediments,
and sorting and redistribution of coarser materials in the sediment matrix along the
slope of the bench or beach. If offshore currents are present, materials may be
redistributed along the direction of flow. Where lake margins intersect with lenses or
large exposures of poorly consolidated bedrock (e.g., carbonate cemented sandstones,
formations containing large quantities of gypsum, etc.), rising and falling water coupled
with wave action can, over time, result in undercutting and collapse. Lithic artifacts
may suffer edge damage or become water-worn, bone items may be splintered or
deteriorate completely, and entire classes of cultural materials (i.e., basketry, vegetal
food remains, etc.) can be lost as a result of repeated episodes of exposure and
inundation.

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In general, sites within the range of a reservoir’s historic high and low elevations that
have been repeatedly inundated and exposed can be expected to have suffered the
greatest amount of damage. Since its equalization with Lake Mead in 1974, surface
elevations for Lake Powell have fluctuated between 3708 and 3627 feet msl. Sites
located between these elevations can thus be expected to have suffered moderate to
severe levels of inundation damage and are unlikely to have qualities that would qualify
them for consideration as historic properties eligible for potential listing on the NRHP.
Modeling runs indicate there is a 10 percent probability the surface level of Lake Powell
will drop to 2595 feet msl by 2016. Sites situated between 3627 feet msl and the
maximum low of 2595 feet msl predicted by the modeling runs can be expected to have
been damaged as the waters of the lake rose, but in the absence of other factors (i.e.,
strong subsurface currents, landslides, etc.), damage should be less than that anticipated
for sites located at higher elevations. Given this, there is a slight possibility sites
located between 3627 and 2595 feet might retain some quality that would qualify them
for listing on the NRHP.
Lake Mead rose to its historic high elevation of 1225.5 feet msl in 1983 and has
dropped to its historic low elevation of 1083 feet on two occasions. The first drop
occurred during the period extending from 1954 to 1957, while the second occurred
or
during 1965 and 1966. Sites located between 1225 and 1083 feet msl ican be expected
Interto be 7
e
to have suffered inundation damage. Damage to all sites f texpected 201 severe given
o is h 29,
pt.large annual fluctuation range in
the 60-plus years the reservoir has been operating,e
v. D the mber
o 75
reservoir elevation (from 10 to as muchtiasn feet,Noveto the filling of Lake Powell),
prior
a
on
ajo N the historic low on two occasions. Reclamation
and the reduction in pool elevation to ived
Nav
considers it is highly unlikely sites exist between elevations of 1225 and 1083 feet msl
d in 64, arch
cite 168
that will retain any qualities that would qualify them for consideration as historic
14No.
properties eligible for potential listing on the NRHP.
Development and implementation of interim surplus criteria will result in changes in
release patterns and mean monthly flow rates along the Colorado River below Hoover
Dam. The results of the hydrological modeling runs for all interim surplus criteria
alternatives indicate there will be an increase in mean monthly flow rates from Hoover
Dam downstream to Parker Dam, while mean monthly flow rates below Parker Dam
will decrease.
The Colorado River drains a vast watershed covering portions of seven states. Prior to
construction of Hoover Dam, discharge rates along the river varied seasonally,
averaging 20,000 cfs with peak flows in excess of 200,000 cfs, making the river
extremely dynamic and unpredictable in its behavior. Examination of historic maps
during archival work conducted in association with a series of recent cultural resource
inventories in the vicinity of Yuma, Arizona (i.e., Bischoff et al., 1998; Huber et al.,
1998a, Huber et al., 1998b; Sterner and Bischoff 1998), indicated the Colorado River
altered its course several times between the 1840s and the 1950s, in one case
meandering two miles across its floodplain. Geomorphological trenching on the
floodplain in areas behind the modern levees revealed the presence of sedimentary

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deposits characteristic of a high energy fluvial environment. Such deposits are unlikely
to contain in situ cultural remains. Inventory of several parcels located on the
floodplain was also revealing. Only recent trash was found on parcels located inside the
levee system, while the earliest cultural materials identified on parcels outside the
levees did not pre-date construction of the levee. Prehistoric cultural remains were
confined to locations on the first terrace above the 100-year floodplain. The site
patterning observed during these studies is doubtless applicable in a general way to
other valleys along the reach of the Colorado River below Hoover Dam.
Flow releases associated with development and implementation of interim surplus
criteria will be within existing operational limits. Increases in flow rates for the reach
of the Colorado River between Hoover and Parker dams and decreases in flow rates
below Parker Dam do not have the potential to cause effects to historic properties, as the
river in these areas is entrenched and confined in its channel by a system of levees.
Furthermore, studies conducted in the vicinity of Yuma, Arizona, suggest that were
bank erosion to occur, sediments adjacent to the current river channel would most likely
reflect deposition under high-energy fluvial conditions. Sediments deposited under
such conditions are unlikely to contain in situ cultural remains that would possess
qualities that would qualify them for consideration as historic properties potentially
r
eligible for listing on the NRHP.
terio

7
he In
. of t releases201
p of
No surface-disturbing activities will occur as a result t flow er 29, associated with
. De
b
development and implementation of interim surplus ovem as such releases will not
ion v N criteria,
at
require construction of newavajo N Noed on
facilities. v modification of existing facilities would be
ch
in Npotentialrfor iimpacts to the structure or functioning of
necessary; thus there is no
ited 6864, a
cNational Historic Landmark), Parker Dam or Imperial Dam (both of
Hoover Dam (a
1
. 14odetermined eligible for listing on the NRHP).
which have been
N

In conclusion, cultural resources that might exist within the APE for Lake Powell and
Lake Mead have been repeatedly inundated, exposed, and re-inundated, making it
highly unlikely that any retain qualities that would qualify them for consideration as
historic properties eligible for listing on the NRHP. Increases and decreases in mean
monthly flow rates below Hoover Dam do not have the potential to affect historic
properties as flows will be confined to the river channel, which, when not confined by
rocky canyon walls, is contained within levees. Were bank erosion to occur, sediments
adjacent to the channel are of a type unlikely to contain cultural materials. There is
virtually no chance cultural resources retaining qualities that would qualify them for
consideration as historic properties potentially eligible for inclusion on the NRHP exist
within the APE of the present undertaking. Reclamation thus considers development
and implementation of interim surplus criteria to be an undertaking without the potential
to affect historic properties. Pursuant to 36 CFR 800.3(a)(1), having determined
development and implementation of interim surplus criteria to be an undertaking with
no potential to affect historic properties, Reclamation has no further obligations under
Section 106 or Part B of 36 CFR 800.

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Reclamation has prepared a memorandum discussing this issue and has forwarded it to
the Advisory Council on Historic Preservation.

ior
Inter 17
0
f the
pt. o er 29, 2
e
v. D
mb
ation on Nove
jo N
Nava archived
in
cited 16864,
14No.

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3.14 INDIAN TRUST ASSETS
3.14.1 INTRODUCTION
Indian Trust Assets (ITAs) are legal assets associated with rights or property held in
trust by the United States for the benefit of federally recognized Indian Tribes or
individuals. The United States, as trustee, is responsible for protecting and maintaining
rights reserved by, or granted to, Indian Tribes or individuals by treaties, statutes and
executive orders. All Federal bureaus and agencies share a duty to act responsibly to
protect and maintain ITAs. Reclamation policy, which satisfies the requirement of
Interior’s Departmental Manual at 512 DM 2, is to protect ITAs from adverse impacts
resulting from its programs and activities whenever possible. Reclamation, in
cooperation with Tribe(s) potentially impacted by a given project, must inventory and
evaluate assets, and then mitigate, or compensate, for adverse impacts to the asset.
While most ITAs are located on a reservation, they can also be located off-reservation.
Examples of ITAs include lands, minerals, water rights and hunting and fishing rights.
ITAs include property in which a Tribe has legal interest. For example, tribal
entitlements to Colorado River water rights established in each of the Basin States
pursuant to water rights settlements are considered trust assets, and erior
t the reservations of
these Tribes may or may not be located along the river. The present perfected federal
he In 2017
of t
reserved rights are rights held directly by the tribal entities for r 29,
ept. bethe reservations in whose
v. D
m
name the rights are listed in the Decree.iontribe may also have other off-reservation
at A on Nove
N into account.
o
interests and concerns that must jbe taken ed
ava
v

in N
rchi
ited into64, a
c
Reclamation has entered 68 government-to-government consultations with potentially
4-1
o identify and address concerns for ITAs. The Tribes include those in
affected Tribes to . 1
N
the Ten Tribes Partnership whose landholdings are situated along the Colorado River
and various tributaries in the Upper and Lower Basins. Additionally, meetings have
been held with the central Arizona Tribes served by CAP facilities, the Coachella
Valley Consortium of Mission Indians and other interested Tribes within the Lower
Colorado Region. Through meetings and discussions among the Tribes, BIA and
Reclamation staff (see Chapter 5), the following sections describe ITAs that have been
identified to have the potential to be impacted by interim surplus criteria.
3.14.2 TEN TRIBES PARTNERSHIP
The Tribes comprising the Ten Tribes Partnership are listed below together with the
states in which their reservations are located:

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Northern Ute Tribe
Jicarilla Apache Tribe
Navajo Nation
Southern Ute Indian Tribe
Ute Mountain Ute Tribe
Fort Mojave Indian Tribe
Chemehuevi Tribe
Colorado River Indian Tribes
Quechan Indian Tribe
Cocopah Indian Tribe

CHAPTER 3

Utah
New Mexico
Arizona, New Mexico and Utah
Colorado
Colorado and New Mexico
Arizona, Nevada and California
California
Arizona and California
Arizona and California
Arizona

The CRSS demand database used for the model analysis in this FEIS includes discrete
representation of the Ten Tribes’ demand schedules through “demand nodes” in the
model. The Tribal demands and their respective points of diversion were obtained from
the Tribes in the summer of 2000. The schedules and the full quantified entitlements on
which they are based are shown in Attachment Q. The following discussion describes
the Ten Tribes’ water rights by Tribe.
3.14.2.1

NORTHERN UTE INDIAN TRIBE – UINTAH AND OURAY RESERVATION

erior

The Northern Ute Tribe is located in northeastern Utah in the e Int River 7
h Green 20 watershed.
. of t two federal1
Quantification of the Tribe’s water rights began inept with r 29,
court Decrees
D 1923
e
that quantified the water rights for the Uintah Indianovemb Project (UIIP). A 1960
Irrigation
n v.
atio on N
report, commonly referred tovajtheN
as o “Decker Report,” divided lands on the reservation
a groups haved
ive
into seven groups. ThoseN
d in land4, arch served as the basis for discussions of
c te 1686
settlement of thei Tribe’s water right claims over the subsequent 40 years. Congress
4ratified a 1990No. 1
tabulation of the Tribe’s water rights in 1992 subject to re-ratification by
the Tribe and State of Utah. That tabulation utilizes the Decker Report’s land groups as
follows:
1. UIIP lands with water rights decreed by the federal court in 1923, and certified by
the State of Utah on the Lakefork, Yellowstone, Uinta and Whiterock rivers.
Priority date - October 3, 1861.
2. UIIP lands with water rights certificated by the State of Utah served from the
Duchesne River including the towns of Duchesne, Randlett and Myton. Priority
date October 3, 1861.
3. Lands that are or can be served from the Duchesne River through UIIP which are
not certificated by the state. Priority date would be October 3, 1861.
4. Lands found to be productive and economically feasible to be irrigated from
privately constructed ditch systems on the Duchesne River or its tributaries above
Pahcease Canal. Priority date would be October 3, 1861.

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5. Lands susceptible to irrigation and proposed to be developed within the Central
Utah Project. Priority date would be October 3, 1861.
6. Lands east of the Green River served from the White River for which Applications
to Appropriate Water were once filed with the State of Utah.
7. Lands east of the Green River found to be productive and economically feasible to
be irrigated from privately constructed ditch systems now in operation or to be
constructed along the Green River, White River, Willow Creek, Bitter Creek, Sweet
Water Creek and Hill Creek.
Tables quantifying the Tribe's diversion and depletion rights as tabulated in the 1990
Tabulation (but not yet ratified by the Tribe or state) are included in the Ten Tribes
Depletion Schedule (Attachment Q). The diversion rights total approximately
480,000 af with depletions of 248,943 af. The water rights appurtenant to the Group 5
Duchesne Basin lands are proposed to be transferred to the Green River with a seven
percent reduction explaining the difference in the table totals. Current water diversions
by the Northern Ute Tribe are approximately 250,000 afy for irrigation applications and
a small amount of M&I use for oil and gas and a small culinary water system.

rior

The Northern Ute Tribe has five demand points modeled in he CRSS: two demand
the Inte
f t River2017 point on
points on the Green River, two demand points on the tDuchesne 29, and one
p.o
. De ember
the White River.
v
ion v

t
No
j Na v
vaIo hiRed on
A Na
3.14.2.2 JICARILLAin PACHE NDIAN ESERVATION
rc
ited 6864, a
c
1Indian
The Jicarilla Apache 4-1 Reservation is located in the upper reaches of the San Juan
No.
River Basin and the Rio Chama Basin in northwestern New Mexico. The reservation
straddles the Continental Divide.
Pursuant to the Jicarilla Apache Tribe Water Rights Settlement Act (“Settlement Act”),
the Tribe is authorized to divert 40,000 afy from the San Juan River Basin, 32,000 afy
of which may be depleted. The Settlement Act provides the Tribe the right to divert
33,500 afy or deplete 25,500 afy from either the Navajo Reservoir supply or directly
from the Navajo River as it crosses the Jicarilla Apache Indian Reservation. The
Settlement Act also authorizes the Tribe to divert and deplete 6,500 afy from the San
Juan River Basin through the transmountain San Juan-Chama Project. The Jicarilla
Apache Tribe agreed to subordinate its 1880 priority date for the 40,000 afy (diversion)
of “future use” federal reserved water rights in exchange for the 1955 priority date
associated with the two federal projects. The Tribe’s agreement to subordinate its 1880
priority date for the 1955 date is discussed in a settlement contract between the Jicarilla
Apache Tribe and the Secretary. The settlement contract is ratified by the Settlement
Act. These are fully adjudicated rights, which, by virtue of the Settlement Act, the Tribe
may market to the full extent that the law allows. The Tribe’s long-term plans for this
water include both off-reservation leasing and on-reservation development.

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In addition to these “future use” water rights adjudicated in accordance with the
Settlement Act, the Jicarilla Apache Tribe also has adjudicated rights to divert 5,683.92
afy or to deplete 2,195 afy, whichever is less, for historic and existing water uses. Thus,
the Jicarilla Apache Tribe’s total water diversion rights from the San Juan River Basin
amount to 45,683 afy and the Tribe’s overall depletion rights from the San Juan Basin
total 34,195 afy.
In the CRSS model, the Jicarilla Apache Tribe is represented by four demand points:
There is a single node on the upper San Juan River for the current on-reservation uses of
the Tribe and those Reclamation assumed were planned for the future. The Tribe’s
portion of the San Juan – Chama export diversion is in an existing demand point and
does not need to be separated. During 2000, the Jicarilla Apache Tribe anticipates
entering into a lease of 16,200 afy through 2025 to Public Service Company of New
Mexico for depletion at the San Juan Generating Station. In addition, the Tribe
anticipates entering into other short-term off-reservation water leases, ultimately
preserving some off-reservation leases in 2060 while allowing the Tribe to use the
majority of its San Juan River Basin depletions on-reservation. In order to show the
change in water leases, a new demand point has been added to show the Jicarilla water
going to the power station and future changes in deliveries. The Tribe is investigating
o
the feasibility of leasing 7,500 afy of water to the City of Gallup via the r
nteri Gallup-Navajo
Municipal Water Supply Project. The Jicarilla lease portionhe the project 7 a new
of I
01 is
ft
pt. o er 29, 2
demand point in the CRSS model.
. De
b

nv
em
Natio d on Nov
R ajo
3.14.2.3 NAVAJO INDIANavESERVATION
e
in N 4, archiv
d
cite 168 in
The Navajo Nation is located6 northeastern Arizona, southeastern Utah and
14northwestern New. Mexico. Navajo reserved water rights to the mainstream Colorado
No

River, the Little Colorado River and the San Juan River basins are not adjudicated. The
Navajo Indian Irrigation Project was authorized by P.L. 87-483. When authorized, the
project was envisioned as a gravity irrigated system with an average annual diversion of
508,000 afy, and a resulting depletion of 254,000 afy. Since authorization in 1962, the
project has been re-designed as a pressurized sprinkler system with an anticipated
average annual diversion of 337,500 afy, and a resulting depletion of 270,500 afy. The
priority date for this diversion and depletion is not later than October 16, 1957.
The CRSS model includes six demand points for the Navajo Nation. There is a demand
point for NIIP on the San Juan River upper reach. Current use and development data
listed for the NIIP demand point are from the development schedule in the NIIP
Biological Assessment dated June 11, 1999. The Navajo Nation also has a small share
in the Animas-La Plata Project (ALP) of 4,680 af of withdrawal and 2,340 af of
depletion annually. This future withdrawal and use has been accounted for in the CRSS
model by splitting the existing ALP M&I node for New Mexico uses and adding a
separate point on the Upper San Juan Reach for the Tribe’s ALP water.

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Present uses in the San Juan River Basin for project areas other than the NIIP have been
quantified in the hydrology models of the basin in the formulation of the Animas-La
Plata Project Draft EIS. CRSS demand points exist for the future Gallup-Navajo
Project showing 5,000 acre-feet of depletion in Arizona and 17,500 acre-feet of
depletion in New Mexico. The existing point was updated to include the Cudei
Irrigation Project with the Hogback node, as these projects will soon be combined into a
single diversion. A demand point was added to the CRSS to include the existing
Fruitland, New Mexico project in the model. Other minor uses on the Navajo
Reservation have been included in natural flow calculations and are not included as
consumptive demands in the CRSS model.
The Navajo Nation currently operates a marina at Antelope Point on Lake Powell. The
boat ramp is not operational when the lake level is below elevation 3,677 feet msl. See
Section 3.9.2.3.1, Lake Powell, regarding impacts to Lake Powell elevations.
3.14.2.4

SOUTHERN UTE RESERVATION

The Southern Ute Indian Tribe is located in southwestern Colorado just west of Navajo
Reservoir. The Tribe has settled its water rights pursuant to agreement with the State of
Colorado and pursuant to 1988 federal legislation effective Decemberior 1991. The
er 19,
settlement requires the construction of the Animas-La Plata he Int The 17 has the
Project.
Tribe
of
, 2 La
. the tAnimas and0 Plata Rivers
right to reopen the adjudication of their water rightspt
De on implementation. The
er 29
if certain agreed upon dates are not mettiregarding projectmb
n v.
a o of n Nove
agreement provides the Tribevajo a varietyd odirect flow rights with priorities ranging
with N
ve
Na
from 1868 to 1976 in streams and archi passing through the Southern Ute Reservation.
d in
, rivers

cite 16864
The CRSS model . 14 demand points for the Southern Ute Tribe. In the model, the
Nohas two

Present Level - Colorado Agriculture demand point on the San Juan River has been split
to separate Southern Ute Tribal uses from non-reservation uses.
The Tribe also has a right to 39,525 acre-feet of water with 19,762 acre-feet of
depletion from the future ALP with a project priority of not later than 1966 for M&I
use. To account for the Southern Ute portion of the water use, the demand point in
Colorado was split into three to separate Southern Ute, other tribes and non-tribal uses.
3.14.2.5

UTE MOUNTAIN UTE INDIAN RESERVATION

The Ute Mountain Ute Tribe is located in the southwestern corner of Colorado with a
small part in northwestern New Mexico. The Tribe has settled its water rights pursuant
to agreement with the State of Colorado and pursuant to 1988 federal legislation
effective December 19, 1991. The settlement requires the construction of the AnimasLa Plata Project. If it should prove impossible to construct this project, the Tribe has the
right to reopen the adjudication of their water rights on the Animas and La Plata Rivers.
The agreement provides the Tribe with a variety of direct flow rights with priorities

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ranging from 1868 to 1985 in three streams, the Mancos River, San Juan River and
Navajo Wash, which pass through the Ute Mountain Ute Reservation.
The CRSS model has four demand points for the Ute Mountain Ute Tribe. In the model
the Present Level - Colorado Agriculture demand point on the Lower San Juan River
was split in two to separate Ute Tribal uses.
The Tribe also possesses 25,180 acre-feet of storage with 19,260 acre-feet of depletion
per year from the Dolores Project for agricultural and other uses with a project priority
of not later than 1963. The Dolores Project is accounted for in the CRSS model at two
points, one of which is for the Ute Mountain Tribal water use.
The Ute Mountain Ute Reservation will have a share of the water in the future ALP.
The Tribe will receive 39,525 af of withdrawal and 19,762 af of depletion rights from
the ALP as it is now formulated. This water is intended for M&I use on the reservation.
To account for the Ute Mountain Ute portion of the water use, the demand point in
Colorado was split into three separate parts: Ute Mountain Ute Tribe, other Tribes and
non-Tribal uses.

ior
Inter 17
0
f the
The Fort Mojave Indian Reservation is located in the tLower Colorado River Basin
p . o er 29, 2
e
.D
where Nevada, Arizona and California meet.vThe Tribe possesses present perfected
mb
ation stem of the e
Nov Colorado River in all three of
federal reserved water rights from the main on
ajo N
d
the states that contain in Nav land, pursuant to the Decree in Arizona v. California
reservation rchive
a
d
, and 1984). Since the original Decree was entered,
ci Decrees (1979
and supplementalte
6864
4-1been added to the reservation along with rights to 6.464 acre1,102 acres of No. have
land 1
3.14.2.6

FORT MOJAVE INDIAN RESERVATION

feet per acre of water as specified in the 1979 Decree. The amounts, including added
lands, priority dates, and state where the water rights are perfected, are as follows:
Amount (afy)

Acreage

Priority Date

State

27,969

4,327

September 18, 1890

Arizona

75,566

11,691

February 2, 1911

Arizona

103,535

16,018

13,698

2,119

September 18, 1890

California

12,534

1,939

September 18, 1890

Nevada

129,767

20,076

Arizona subtotal

Total

The Fort Mojave Indian Tribe has exercised its water rights in California in excess of
the amounts currently decreed. In it's June 19, 2000 Opinion, the United States

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Supreme Court accepted the Special Master’s uncontested recommendation and
approved the proposed settlement of the dispute respecting the Fort Mojave Indian
Reservation. Under the settlement, the Tribe is awarded the lesser of an additional
3,022 af of water or enough water to supply the needs of 468 acres.
The attached tables are estimates of use based upon calculations derived from records of
electrical consumption at the various pump stations and are not from measured flows.
The CRSS model contains four demand sub points for the Tribe’s water diversions,
which are divided among three states. The points are on the Lake Mohave reach of the
model, and are further divided into sub points by state. A separate sub point is included
for Reservation Land development, but has a diversion of zero af at this time. Current
depletion amounts for the CRSS model nodes have been updated to reflect the most
recent consumptive use numbers provided by the Lower Colorado River Accounting
System (LCRAS) report for calendar year 1998. Future depletions at full development
are calculated as the greater of 70 percent of diversion rights and the per acre rate of
consumptive use from the LCRAS report multiplied by the full right acreage of the
Tribe.
3.14.2.7

CHEMEHUEVI INDIAN RESERVATION

erior

Int
The Chemehuevi Indian Reservation is located in southern tCalifornia near7
Lake
f he water rights from the
o
. reserved 29, 201
t
Havasu. The Tribe possesses present perfected federal
Dep mber
main stem of the Colorado River pursuant n v. Decree in Arizona v. California and
to the
ove
atio
supplemental Decrees (1979 vajo N The amounts, priority dates, and state where
and 1984). ed on N
Na
hv
the rights are perfected, are as follows: i
d in
, arc
cite 16864
14Amount o.
Acreage
N (afy)
11,340

1900

Priority Date

State

February 2, 1907

California

The lands of the Chemehuevi Tribe are mostly on the plateau above the shoreline of
Lake Havasu. Present agricultural water use is limited. Currently, the CRSS model
includes a demand point for the Chemehuevi Reservation on the Lake Havasu reach of
the model. Current depletion amounts for the CRSS model nodes have been updated to
reflect the most recent consumptive use numbers provided by the LCRAS report for
calendar year 1998. Future depletions at full development are calculated as the greater
of 70 percent of diversion rights and the per acre rate of consumptive use from the
LCRAS report multiplied by the full right acreage of the Tribe.
3.14.2.8

COLORADO RIVER INDIAN RESERVATION

The Colorado River Indian Reservation is located in southwestern Arizona and southern
California south of Parker, Arizona. The Tribes possess present perfected federal
reserved water rights from the main stem of the Colorado River pursuant to the Decree

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in Arizona v. California and supplemental Decrees (1979 and 1984). The amounts,
priority dates, and state where the rights are perfected, are as follows:
Amount (afy)

Acreage

Priority Date

State

358,400

53,768

March 3, 1865

Arizona

252,016

37,808

November 22, 1873

Arizona

51,986

7,799

November 16, 1874

Arizona

662,402

99,375

10,745

1,612

November 22, 1873

California

40,241

6,037

November 16, 1874

California

3,760

564

May 15, 1876

California

54,746

8,213

717,148

107,588

Arizona subtotal

California subtotal

Total

erior
Intthe Colorado River
The CRSS Model presently has three demand sub-nodes listed for 2017
f the 9,
pt. o diversions are split between
Tribe on the reach above Imperial Dam number. The waterber 2
v. De ve
ion demands andm separate sub-node for future
sub-points for California demands, Nat
Arizona
n No a
v jo h depletion
pumped diversions in Arizona.aCurrentived o amounts for the CRSS model nodes
in Na
rc
have been updated to reflect the ,most recent consumptive use numbers provided by the
ited 6864 a
c
-1
LCRAS report for.calendar year 1998. Future depletions at full development are
o 14 of 70 percent of diversion rights and the per acre rate of
N
calculated as the greater
consumptive use from the LCRAS report multiplied by the full right acreage of the
Tribe.
3.14.2.9

QUECHAN INDIAN RESERVATION (FORT YUMA)

The Fort Yuma Indian Reservation (Quechan Tribe) is located in southwestern Arizona
and southern California near Yuma, Arizona. The Tribe possesses present perfected
federal reserved water rights from the main stem of the Colorado River pursuant to the
Decree in Arizona v. California and supplemental Decrees (1979 and 1984). The
amounts, priority dates and state where the rights are perfected, are as follows:
Amount (afy)

Acreage

Priority Date

State

51,616

7,743

January 9, 1884

California

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A recent Supreme Court decision issued on June 19, 2000 allows the Tribe to proceed
with litigation to claim rights to an additional 9,000 acres of irrigable lands. Proving
this claim would increase the water rights for the reservation.
Water for the Quechan Tribe is diverted from the Colorado River at Imperial Dam and
delivered through the Yuma Project Reservation Division-Indian Unit. The Tribe has
other small uses at homestead sites south of Yuma, Arizona. The current water uses
shown in the following tables include only Quechan Indian Tribe uses within the Fort
Yuma Reservation. These uses are accounted for in the CRSS model with one
diversion point on the Imperial Dam Diversions reach. The current withdrawal and
depletion values have been updated to reflect the most recent consumptive use numbers
provided by the LCRAS report for calendar year 1998. Future depletions at full
development are calculated as the greater of 70 percent of diversion rights and the per
acre rate of consumptive use from the LCRAS report multiplied by the full right acreage
of the Tribe.
3.14.2.10 COCOPAH INDIAN TRIBE
The Cocopah Indian Reservation is located in southwestern Arizona near Yuma,
Arizona. The Tribe possesses present perfected federal reserved wateror
eri rights from the
main stem of the Colorado River pursuant to the Decree in the Int v. California and
Arizona
017
f
supplemental Decrees (1979 and 1984). The amounts, priorityrdates, 2 state where
pt. o e 29, and
De
b
the rights are perfected, are as follows: tion v.
ovem

N
Na
vajo hived on
Amount (afy) N
Acreage
Priority Date
in a
rc
ited 6864, a
c 7,681 1
1,206 September 27, 1917
14No.

State
Arizona

2,026

318

June 24, 1974

Arizona

1,140

190

1915

Arizona

10,847

1,714

Total

The rights listed above and in the attached tables include only that water diverted
directly from the Colorado River at Imperial Dam. In addition to these rights, the Tribe
has numerous well permits that divert groundwater that may be connected to the
Colorado River within the boundaries of the United States (studies are ongoing).
The 1974 present perfected federal reserved right for the Cocopah Indian Reservation is
unique because of its more recent priority date. The 1979 supplemental Decree in
Arizona v. California specifies that in the event of a determination of insufficient
mainstream water to satisfy present perfected rights pursuant to Article II (B) (3) of the
1964 Decree, the present perfected rights set forth in paragraphs (1) through (5) of
Article II (D) of the Decree must be satisfied first. The 1984 supplemental Decree in
Arizona v. California recognized the present perfected federal reserved right for the

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Cocopah Indian Reservation dated June 24, 1974, and amended paragraph (5) of Article
II (D) of the Decree to reflect this 1974 right.
The Tribe is involved in litigation to claim rights to a total of 2,400 acres of irrigable
lands. Proving this claim would further increase the water rights for the reservation.
Water diversions for the Cocopah Indian Tribe are listed at two demand nodes in the
CRSS model on two of the model reaches. A demand point on the Imperial Dam
diversion reach accounts for all of the Tribe’s rights and current uses in Arizona.
Another node is provided for future pumped diversions below Imperial Dam, but it has
a diversion of zero af at the current time. Current depletion amounts for the CRSS
model nodes have been updated to reflect the most recent consumptive use numbers
provided by the LCRAS report for calendar year 1998. Future depletions at full
development are assumed to be 100 percent of the diversions as the location of the
reservation prevents a return flow within Arizona.
3.14.2.11 ENVIRONMENTAL CONSEQUENCES
The Ten Tribes have a significant amount of undeveloped water rights. The current
availability of surplus water on the Colorado River is primarily a direct result of unused
rior
existing entitlements, including those of the Tribes. The Ten e Intehave raised
Tribes
17
th
significant concerns that interim surplus criteria could: 1)ffoster a 9, 20 on surplus
pt. o er 2reliance
De
b
water on the part of other entitlement holders; .2) providemdisincentive for those
ion v Nove a
at development; and 3) have the practical
entitlement holders to support ajo NTribal d on
future
Nav abilityitoe
effect of diminishing the Tribes’ arch v utilize their entitlements.
d in

cite 16864,
The interim surplus 14
No. criteria will not alter the quantity or priority of tribal entitlements.

In fact, as noted by the description of the Ten Tribes’ water rights above, the Tribes
have the highest priority water rights on the Colorado River. Surplus determinations
have been made since 1996. The interim surplus criteria would not make any additional
surplus water available as compared with current conditions, but rather would provide
more objective criteria for surplus determinations. Moreover, the preferred alternative
would quantify the amounts of surplus water to be made available. Reclamation does
not believe that identifying the limited amounts of surplus water will provide any
additional disincentives for Tribal water development. Interim surplus criteria are
intended to assist in the effort to reduce the overreliance by California on surplus water.
The selection of any of the alternatives of this proposed action does not preclude any
entitlement holder from using its water.
3.14.2.11.1

Upper Basin Mainstem Tribes

As expected, the model analyses showed that interim surplus criteria would have no
effect on Upper Basin deliveries, including the Tribal demands above Lake Powell. As
noted in Section 3.4.4.4, the normal delivery schedules of all Upper Basin diversions
would be met under most water supply conditions. Only under periods of low

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

hydrologic conditions would an Upper Basin diversion be shorted. Although the model
is not presently configured to track the relative priorities under those conditions, such
effects are identical under baseline and all alternatives.
3.14.2.11.2

Lower Basin Mainstem Tribes

Under normal conditions, deliveries to Lower Basin users are always equal to the
normal depletion schedules, including those for the Tribes. Under shortage conditions,
only CAP and SNWA share in the shortage until CAP goes to zero (which was not
observed in any of the modeling runs done for this EIS). Therefore, the Tribes of the
Ten Tribe Partnership in the Lower Basin would receive their scheduled depletion, with
the exception of the Cocopah Tribe that has some Arizona Priority 4 water. However,
adoption of the interim surplus criteria would not significantly increase the risk of
shortages to holders of Arizona Priority 4 water. For example, the modeling analysis
indicates that under the preferred alternative, the occurrence of Priority 4 shortages
would be approximately four percent greater than under baseline conditions.
3.14.3 TRIBES SERVED BY CENTRAL ARIZONA PROJECT
Various Indian tribes and communities in central Arizona have been provided water
rior
pursuant to CAP contracts by either direct Secretarial actions e Ithrough negotiated
or nte
017
f th
water rights settlements (CAP Tribes). CAP water has played a primary role in
pt. o er 29, 2
. De
b
facilitating water rights settlements in Arizona; it is expected to play such a role in the
ion v Novem
at
future. In fulfillment of the trust o N
o the
aj responsibility,n impact of shortages upon the water
i primary
NavTribeschaved concern.
supplies provided to the CAP
ar is
d in

cite 16864,
14The Tribes that receive CAP water are listed below together with the counties in which
No.
their reservations are located:

Gila River Indian Community
San Carlos Indian Tribe
Tohono O’Odham Nation
Tonto Apache Tribe
Yavapai-Apache Indian Community
Fort McDowell Indian Community
Salt River Pima Maricopa Indian Community
Ak Chin Indian Community
Pascua-Yaqui Tribe
Yavapai-Prescott Indian Tribe
3.14.3.1
3.14.3.1.1

Maricopa and Pinal
Gila, Pinal and Graham
Pina, Maricopa and Pinal
Gila
Yavapai
Maricopa
Maricopa
Pinal
Pima
Yavapai

WATER RIGHTS SETTING
CAP Priority Scheme

An understanding of the CAP priority scheme is vital in order to understand how
shortages could potentially impact the different priorities of CAP water and CAP water

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CHAPTER 3

users, including Indians. Traditionally, Reclamation’s view is that the CAP
has five priorities of water rights. The first priority is known as Colorado River water.
Colorado River water was secured by the United States for settlement of certain Indian
water claims. The second priority includes M&I water and Indian Homeland water.
The third priority is Indian agricultural water that was allocated to tribes by the
Secretary but was not classed as Homeland water. The fourth priority is M&I water
above the first 510,000 af of the M&I allocation (equal to 128,823 af).
The fifth priority is non-Indian agricultural water. The fifth priority is available to
several users besides non-Indian agriculture. For example, 312,898 af of fifth priority
CAP water, called Excess water, is available to the Central Arizona Groundwater
Recharge District (CAGRD) for groundwater recharge, non-Indian agriculture, and the
Arizona Water Banking Authority (AWBA) for in-lieu recharge and direct groundwater
recharge. The remaining portion of fifth priority CAP water, 51,800 af, is non-Indian
agricultural water that is assumed to be allocated to Indian users.
The priorities discussed in this section are internal to the CAP and must not be confused
with priorities of water entitlements along the mainstream of the Colorado River.
The future allocation of CAP water to some CAP priorities is not definitive because of
ior
In er 17
the dual possibility of finalizing or not finalizing two settlements. tOne settlement is
0
f the entities
among the Gila River Indian Community (GRIC),ept. o Arizona9, 2 and the
certain
r2
e
v D
United States (GRIC Settlement). The tsecond.settlementmb CAP Settlement
a ion on Nove is the
between the United States and ajo Centraled
the N
Arizona Water Conservation District
Nav archiv
(CAWCD). Under d in
shortage, potential impacts to Indian CAP water users differ
te
6
c whether CAP 4, is allocated under settlement or without settlement.
depending upon i
-168 water

No.

14

Table 3.14-1 provides, in units of afy, allocations of CAP water to CAP priorities for
certain Indian Tribes or communities under two scenarios. The first scenario, Likely
Future Without, reflects assignment of water rights absent final GRIC and CAP
settlements. The second scenario, With Settlement, assumes final GRIC and CAP
settlements. The primary difference between the two scenarios is that with final
settlements, GRIC is assigned an additional 102,000 af of non-Indian agricultural water
and the United States reserves 69,800 af of other non-Indian water for future water
rights settlements.
Table 3.14-2 reflects the CAP priority scheme under the two scenarios and identifies the
points at which shortages on the Colorado River begin to impact different priorities of
CAP water. Normal year diversions of CAP water are assumed to be 1.5 maf.
Reductions for system losses result in deliverable water of 1,415,000 af. The effects of
shortages on CAP water associated with various priorities is as follows:
Fifth Priority. In the event of a shortage on the river restricting deliveries of
CAP water to 925,000 af, the fifth priority water rights would go unfulfilled.

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AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

CHAPTER 3

Table 3.14-1
Central Arizona Project Indian Water Allocations
Unit: Acre-Feet Annually
Likely Future
without GRIC (afy)

Indian Tribe and Allocation
Gila River Indian Community
Indian Allocation
Indian Priority – HVID
Settlement Water
M & I – ASARCO
Non-Indian Agric.-RWCD
Other
Total
San Carlos Indian Tribe
Indian Allocation
M & I Priority
Indian Reallocation (Ak Chin)(minus losses)

With GRIC
Settlement (afy)

17,000
18,600
226,500

17,000
18,600
102,000
328,500

12,700
18,145
30,800

12,700
18,145
30,800

61,645

61,645

45,800
28,200
74,000

45,800
28,200
74,000

128
128

128
128
1,200

25,000
50,000
75,000

25,000
50,000
75,000

500
500

500
500

500
500

500
500

309,828
54,428
255,400
70,900
31,733
35,145
51,800
1,518
498,424

309,828
54,428
255,400
70,900
31,733
35,145
153,800
1,518
69,800
670,224

603,678
312,898
1,415,000

Indian Allocation
Total
Fort McDowell Indian Community

173,100
17,800

1,200
1,200

Total
Tohono O'Odham Nation (San Xavier, Schuk Toak, Chui-Chu)
Indian Allocation
Non-Indian Agric.
Total
Tonto Apache Tribe
Indian Allocation
Total
Yavapai-Apache Indian Community

173,100
17,800

603,678
141,098
1,415,000

ior 1,200
Inter 17
the
0 4,300
f 4,300
Indian Allocation
pt. o 13,933r 29, 2 13,933
Indian Priority-HVID
e
v. D
mbe
Total
18,233
18,233
ation on Nove
Salt River Pima Maricopa Indian Community N
o
Indian Allocation
13,300
13,300
ed
avaj
Colorado River (net of N
20,900
20,900
in losses)4, archiv
d
Non-Indian te
5,000
5,000
ci Agric. 1686
Total 439,200
39,200
.1
Ak Chin Indian Community
No

Indian Allocation
Colorado River
Total
Pascua Yaqui Tribe
Indian Allocation
Total
Yavapai-Prescott Indian Tribe (assigned to Scottsdale)
Indian Allocation
Total
Total Indian Allocations
Indian Allocation
Homeland
Agricultural
Colorado River
Indian Priority-HVID
M & I Priority
Non-Indian Agric.
Unassigned HVID
Future Settlements (agric. priority)
Total
Municipal and Industrial Water Supply
Non-Indian Agricultural Water Supply
Total Normal Water Supply
Source:

Central Arizona Project 1996 Water Supply Study for Stage II Cost Allocation
Draft EIS for allocation of CAP water supply -- June, 2000

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CHAPTER 3

Fourth Priority. Subsequent reductions would impact M&I water amounts in
excess of 510,000 af. Consequently, any M&I priority water which has been
reallocated for Indian use would also be affected.
Third Priority. The next block of water to be impacted by shortages is a portion
of the Indian agricultural water. The deliveries to GRIC would be reduced by
25 percent of its agricultural allocation; all other tribes having Indian
agricultural water would be reduced by 10 percent of their respective
agricultural allocations.
Second Priority. The remaining M&I and Indian priority water would be
reduced on a pro rata basis as water deliveries decrease.
First Priority. Colorado River water would be unavailable only if a shortage
were severe enough that no diversion could be made into central Arizona.
3.14.3.1.2

Examples of Reductions of CAP Water Deliveries

Table 3.14-3 demonstrates the incidence of reductions to the CAP Indian supplies
during shortage on the Colorado River under the Likely Future Without r
scenario.
terioto show the
Various quantities of CAP water deliveries have been assumed in order 7
he In that represents a
varying impacts between Indian tribes. The amountpt. CAP water9, 201
of of t
2
e
division between one priority and the nextn v. Dpriority isber
higher
m referred to here as a “break
ve
io
point.” For example, the estimated Nat point n No the fifth and fourth priorities is
ajo break ed o between
Nav ar
1,050,302 af. A total available CAPchiv supply of 1,050,302 af means that no
d in CAP4waterwater be made. If the shortage decreases the
ci e 1
deliveries of fifthtpriority 686 ,
would
available total No. 14 supply below 1,050,302 af, deliveries of fourth priority CAP
CAP water
water would be impacted. Similarly, between the fourth and third priorities, the break
point is 921,479 af. The division between the third and second priority is 869,974 af.
Finally, the last break point is 68,400 af. See Section 3.4.4.1.2 for a summary of the
Arizona modeled annual depletions under normal, surplus and shortage conditions.
Reductions in Indian water supplies in the fifth priority are estimated to be 51,800 af.
The affected amount of Indian water supply in the fourth priority is 7,087 af. The third
priority Indian agricultural water affected totals 51,505 af. Indian priority water in the
second priority totals 317,132 af. Finally, the Colorado River priority water held by
Indians totals 68,400 af.
Table 3.14-4 shows the same information as Table 3.14-3, but assumes a final GRIC
and CAP settlement. The same priority scheme is applied as used in the without
settlement scenario. In this instance, GRIC is allocated an additional 102,000 af of nonIndian agricultural water. The amount of 69,800 af of non-Indian agricultural water is
held by the United States for future Indian water rights settlements. As a result, the
potential Indian/federal loss in the fifth priority increases to 223,600 af, as compared
with 51,800 af without settlement. Impacts to the other priorities remain the same.

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.14-14

Pro rata reduction of Indian and M & I water

Second:

Likely

801,574

68,400

GRIC

Future
without

Total

68,4001

801,574

869,9742

Indian agricultural water (reduce 25 % of GRIC ag. water, and 10 % of other Indian ag.)

51,505

6

5

4

921,4793

3.14-15

The traditional USBR interpretation of shortage sharing criteria is used in the analysis of the likely future with and without the GRIC settlement. It is understood
that new shortage sharing criteria are included in the GRIC settlement but the settlement is under negotiation at the current time. Reclamation believes that the
use of the traditional shortage sharing criteria for likely future with GRIC settlement will not have a major effect on the relative difference among the alternatives.

GRIC Settlement" amount is the sum of 153,800 af of reallocated agricultural water and 69,800 af of reallocated agricultural water held by U. S. for future Indian
water settlements
The amount is an estimate of the excess water pool, with and without settlement between the U.S. and CAWCD

Likely Future" amount is 51,800 af of reallocated agricultural water

Amount is the difference between 638,823 af and 510,000 af of M&I priority water

Amount is made up of 43,275 af of GRIC water and 8,230 af of other Indian agricultural water

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS

7

6

5

4

3

1,415,000

1,273,902

1,050,302

921,479

869,974

68,400

Water

With GRIC
Settlement

68,4001

Total Water

Notes:
1
The total represents the Yuma Mesa water (50,000 af) plus Wellton-Mohawk water (22,000 af) minus estimated transmission losses.
2
Total is composed of 510,000 af of M&I water plus 33,251 af of HVID water plus 258,323 af of Indian water after reductions in third priority and losses

Fifth:

Fifth:

Fourth:

Acre-Feet Per Year

ior
Inter 17 51,505
e
(Indian agric. water is that portion of original allocation which is not "Homeland")
of th 29, 20
pt.
r
. De embe1,050,302
M & I water above 510,000 acre feet, including M&I reallocations to Indiansv
128,823
128,823
n
atio on Nov
N
vajo hived
Non-Indian agricultural water reallocated to Indians
51,800 1,102,102
223,600
in Na 4, arc
cited 1686
Excess water (priority = 1, CAGRD, 2, Agric., 3 AWBA )
312,898 1,415,000
141,098
14No.

Colorado River Water – Yuma Mesa and Wellton Mohawk

First:

Third:

CHAPTER 3

Table 3.14-2
7
Traditional Reclamation Priorities for Central Arizona Project Water

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1

226,500

61,645

74,000

128

1,200

18,233

39,200

75,0001

500

500

ior
Inter 17
e
of th 29, 20
pt.
. De ember
v
ation on Nov
N
vajo hived
Na
d in 64, arc
cite 168
o. 14
N

1,518

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.14-16

Ak-Chin values are not additive because system losses on the 50,000 af of Colorado River Priority water are borne by San Carlos Tribe, except in the instance of CAP deliveries restricted to
Colorado River rights only [first priority]. In this case system losses are borne by Ak-Chin.

Total Reductions

First
Priority
Colo. River

M&I
and
Indian

Second
Priority

Third
Priority
Indian Ag.

M&I

Fourth
Priority

Agricultural

Fifth
Priority

CHAPTER 3

Accumulated
CAP
Total
Tohono
Tonto
Yavapai
Pascua Yavapai
Water Reduction GRIC
San Carlos
FMIC
SRPMIC Ak Chin
Unassigned Reductions Reductions
O'Odham Apache Apache
Yaqui
Prescott
per Priority
Supply
HVID
1,415,000
none
none
none
none
none
none
none
none
none
none
115,000
1,300,000
5,865
8,892
1,577
16,334
215,000
1,200,000
10,965
16,625
2,948
30,538
315,000
1,100,000
16,065
24,357
4,319
44,741
364,698
1,050,302
18,600
28,200
5,000
51,800
51,800
50,302
1,000,000
1,339
1,429
2,767
125,302
925,000
3,334
3,559
6,894
128,823
921,479
3,428
3,659
7,087
58,887
21,479
900,000
18,047
1,501
334
555
1,043
21,479
51,505
869,974
43,275
3,600
800
1,330
2,500
51,505
110,392
69,974
800,000
14,072
4,748
3,928
11
105
1,592
1,045
1,964
44
44
133
27,684
169,974
700,000
34,182
11,533
9,542
27
254
3,866
2,538
4,771
106
106
322
67,248
269,974
600,000
54,292
18,317
15,156
43
404
6,141
4,032
7,578
168
168
511
106,812
369,974
500,000
74,402
25,102
20,770
59
554
8,416
5,525
10,385
231
231
701
146,375
469,974
400,000
94,512
31,887
26,384
75
704
10,690
7,018
13,192
293
293
890
185,939
569,974
300,000
114,622
38,672
31,998
91
853
12,965
8,511
15,999
356
356
1,079
225,502
669,974
200,000
134,732
45,457
37,612
107
1,003
15,240
10,005
18,806
418
418
1,269
265,066
769,974
100,000
154,842
52,242
43,226
123
1,153
17,514
11,498
21,613
480
480
1,458
304,630
799,074
68,400
161,197
54,386
45,000
128
1,200
18,233
11,970
22,500
500
500
1,518
317,132
427,524
70,900
0
20,900
47,500
68,400

Table 3.14-3
Reductions in Indian CAP Water Supplies During Times of Shortage on Colorado River
Likely Future Without GRIC Settlement

AFFECTED ENVIRONMENT & ENVIRONMENTAL CONSEQUENCES

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2

1

70,900

799,074

769,974

669,974

569,974

469,974

369,974

269,974

169,974

69,974

51,505

21,479

128,823

125,302

50,302

364,698

315,000

215,000

115,000

Reduction

328,500

161,197

154,842

134,732

114,622

94,512

61,645

54,386

52,242

45,457

38,672

31,887

3,559

1,429

28,200

24,357

16,625

8,892

San Carlos Tohono
Tonto Yavapai
O'Odham Apache Apache
none
none
none
none
none

FMIC

5,000

4,319

2,948

1,577

none

none

SRPMIC Ak Chin

Pascua
Yaqui
none

74,000

45,000

43,226

37,612

31,998

26,384

128

128

123

107

91

75

1,200

1,200

1,153

1,003

853

704

18,233

18,233

17,514

15,240

12,965

10,690

39,200

20,900

11,970

11,498

10,005

8,511

7,018

75,0002

47,500

22,500

21,613

18,806

15,999

13,192

500

500

480

418

356

293

500

500

480

418

356

293

1,518

1,518

1,458

1,269

1,079

890

69,800

69,800

60,288

41,149

22,010

68,400

317,132

304,630

265,066

225,502

185,939

146,375

106,812

67,248

27,684

51,505

21,479

7,087

6,894

2,767

223,600

193,130

131,819

70,508

COLORADO RIVER INTERIM SURPLUS CRITERIA FEIS
3.14-17

Ak-Chin values are not additive because system losses on the 50,000 af of Colorado River Priority water are borne by San Carlos Tribe, except in the instance of CAP deliveries restricted to
Colorado River rights only [first priority]. In this case system losses are borne by Ak-Chin.

599,324

282,192

230,687

223,600

Accumulated
Total
Yavapai Unassigned Reserved Reductions Reductions
Federal per Priority
Prescott
HVID
none
none
none

ior
3,428
3,659
Inter 17
the
20
18,047
1,501
334
555 t. of
1,043
ep 2,500 ber 29,
D
43,275
3,600
800
n v. 1,330 ovem
tio
N
14,072
4,748
3,928
11
105
44
44
133
jo Na ve1,592on1,045 1,964
a
d
v 27 hi 3,866 2,538 4,771 106 106
a
34,182
11,533in N
322
d 9,54264, arc 254
ite
54,292c 18,317
15,156
511
68 43 404 6,141 4,032 7,578 168 168
14-1
74,402 o.
701
N 25,102 20,770 59 554 8,416 5,525 10,385 231 231
3,334

1,339

120,600

104,166

71,097

38,0