RECLAMATION 


Managing Water in the West 

Colorado River Basin 

Water Supply and Demand Study 

Executive Summary 

u.s. Department of the Interior December 2012 

Bureau of Reclamation 
Mission Statements
 

The U.S. Department of the Interior protects America’s natural resources and heritage, 

honors our cultures and tribal communities, and supplies the energy to power our future. 

The mission of the Bureau of Reclamation is to manage, develop, and protect water and related 

resources in an environmentally and economically sound manner in the interest of the American public. 
Colorado River Basin 

Water Supply and Demand Study 

Executive Summary 

U.S. Department of the Interior December 2012 

Bureau of Reclamation 

Executive Summary 

Foreword 

The Colorado River is the lifeblood of the southwestern United States. 

Stretching from the highest peaks of the Rocky Mountains to the Gulf 

of California, it travels over 1,400 miles across a watershed that 

includes seven states within the United States and two states in northern Mexico. Nearly 40 

million Americans rely on the Colorado River system for drinking water and to support livelihoods ranging from farming to recreation. Emphasizing the economic, cultural, and ecologic 

significance of this river, our commitment to sound management for generations to come is 

steadfast. At the forefront of that pledge is the SECURE Water Act, the WaterSMART program, 

and Basin Studies across the West. These programs elevate water planning and management to 

new levels with expanded science, collaboration, and forward thinking. Just as we benefit from 

the planning and works of prior generations, it is our obligation to use the best information 

available to us to prepare for the water management challenges ahead. 

Conducted under the Basin Study Program, the Colorado River Basin Water Supply and
 

Demand Study is the most comprehensive long-term assessment to date of the Colorado River
 

Basin and its invaluable resources. Findings indicate that in the absence of timely action to
 

ensure sustainability, there exists a strong potential for significant imbalances between water
 

supply and demand in coming decades. Through the Study process, a common technical foundation was established, upon which continued dialogue will be built towards actions that will
 

enhance and preserve the future of communities, economies, and ecosystems supported by the
 

Colorado River.
 

As the Basin copes with yet another year in an unprecedented drought extending back to 1999,
 

the challenges of the task at hand are more real than ever. Though these challenges are unprecedented, I am confident that the partnerships forged and strengthened during this Study and over
 

the years will rise to meet the undertaking with vigor.
 

Michael L. Connor,
 

Commissioner, Bureau of Reclamation
 

Executive Summary 

Contents 

1.0 	 Projected Future Water Supply and Demand Scenarios 6 

2.0	 Projected Future Water Supply and Demand Imbalances 9
 

3.0	 Options and Strategies to Resolve Supply and Demand 11
 

Imbalances
 

4.0	 Evaluation of Options and Strategies to Resolve Supply 17
 

and Demand Imbalances
 

5.0	 Study Limitations 24
 

6.0 Future Considerations and Next Steps 26
 

Disclaimer 28
 
Executive Summary 

FIGURE 1 

The Study Area - the hydrologic boundaries of the Basin within the United States, plus the adjacent areas of 

the Basin States that receive Colorado River water 

2 
Executive Summary 

Executive
 

Summary
 

Spanning parts of the seven states of Arizona, 

California, Colorado, New Mexico, Nevada, 

Utah, and Wyoming (Basin States), the 

Colorado River Basin (Basin) is one of the 

most critical sources of water in the West. The 

Colorado River and its tributaries provide 

water to nearly 40 million people for 

municipal use, supply water to irrigate nearly 

5.5 million acres of land, and is the lifeblood 

for at least 22 federally recognized tribes 

(tribes), 7 National Wildlife Refuges, 4 

National Recreation Areas, and 11 National 

Parks. Hydropower facilities along the 

Colorado River provide more than 4,200 

megawatts of electrical generating capacity, 

helping to meet the power needs of the West 

and offset the use of fossil fuels. The 

Colorado River is also vital to the United and loss in the Basin has averaged 

Mexican States (Mexico) to meet both approximately 15.34 maf over the last 10 

agricultural and municipal water needs. years. Because of the Colorado River 

system’s ability to store approximately 60 

The Colorado River system is operated in maf, or nearly 4 years of average natural flow 

accordance with the Law of the River1. of the river, all requested deliveries were met 

Apportioned water in the Basin exceeds the in the Lower Basin despite recently 

approximate 100-year record (1906 through experiencing the worst 11-year drought in the 

2011) Basin-wide average long-term historical last century. However, there have been 

natural flow2 of about 16.4 million acre-feet periodic shortages throughout the Upper 

(maf). However, the Upper Basin States have Basin and the adjacent areas of the Basin 

not fully developed use of their 7.5-maf States that receive Colorado River water. 

apportionment, and total consumptive use3 

1 The treaties, compacts, decrees, statutes, regulations, contracts and other legal documents and agreements applicable to the 

allocation, appropriation, development, exportation and management of the waters of the Colorado River Basin are often 

collectively referred to as the Law of the River. There is no single, universally agreed upon definition of the Law of the River, but it 

is useful as a shorthand reference to describe this longstanding and complex body of legal agreements governing the Colorado 

River. 

2 Natural flow represents the flow that would have occurred at the location had depletions and reservoir regulation not been 

present upstream of that location. 

3 Consumptive use is defined as water used, diminishing the available supply. 

4 Basin-wide consumptive use and losses estimated over the period 2002-2011, including the 1944 Treaty delivery to Mexico, 

reservoir evaporation, and other losses due to native vegetation and operational inefficiencies. 

Lake Mead during drought conditions 

3 
Executive Summary 

The challenges and complexities of ensuring a sustainable 

water supply and meeting 

future demand in an over-allocated and highly 

variable system such as the Colorado River 

have been recognized and documented in 

The Colorado River and its 

tributaries provide water to nearly 

40 million people for municipal use, 

supply water to irrigate nearly 5.5 

million acres of land, and is the 

lifeblood for at least 22 federally 

recognized tribes, 7 National 

Wildlife Refuges, 4 National 

Recreation Areas, and 11 National 

Parks. 

several studies conducted by the Bureau of 

Reclamation (Reclamation) and the Basin 

States over the past several decades. Looking 

ahead, concerns regarding the reliability of 

the Colorado River system to meet future 

Basin resource5 needs are even more 

apparent, given the likelihood of increasing 

demand for water throughout the Basin 

coupled with projections of reduced supply 

due to climate change. 

It was against this backdrop that the Colorado 

River Basin Water Supply and Demand Study 

(Study) was conducted. Funded by 

Reclamation through the Basin Study 

Program under the Department of the 

Interior’s WaterSMART (Sustain and Manage 

America's Resources for Tomorrow) Program 

and the agencies6 representing the Basin 

States, the Study was conducted by 

Reclamation’s Upper 

Colorado and Lower 

Colorado Regions and the 

representatives of the Basin 

States’ agencies. The purpose of the Study was to 

define current and future 

imbalances in water supply 

and demand in the Basin 

and the adjacent areas of 

the Basin States that 

receive Colorado River 

water over the next 50 

years (through 2060), and 

to develop and analyze 

adaptation and mitigation 

strategies to resolve those 

imbalances. The Study did 

not result in a decision as to 

Green River in Utah 

5 Resources include water allocations and deliveries for municipal, industrial, and agricultural use; hydroelectric power generation; 

recreation; fish, wildlife, and their habitats (including candidate, threatened, and endangered species); water quality including 

salinity; flow- and water-dependent ecological systems; and flood control. 

6 The non-Federal cost-share partners are: Arizona Department of Water Resources, the (California) Six Agency Committee, 

Colorado Water Conservation Board, the New Mexico Interstate Stream Commission, the Southern Nevada Water Authority, the 

Utah Division of Water Resources, and the Wyoming State Engineer’s Office. 

4 
Executive Summary 

how future imbalances should or will be 

addressed. Rather, the Study provides a common technical foundation that frames the 

range of potential imbalances that may be 

faced in the future and the range of solutions 

that could be considered to resolve those 

imbalances. 

The Study Area is shown in figure 1 and is 

defined as the hydrologic boundaries of the 

Basin within the United States, plus the 

adjacent areas of the Basin States that receive 

Colorado River water. In many adjacent areas, 

the Colorado River supply is in addition to 

other water supply sources used to meet water 

demands. 

The Study was conducted in collaboration 

with stakeholders throughout the Basin. 

Interest in the Study was broad, and stakeholders included tribes, agricultural users, 

purveyors of municipal and industrial (M&I) 

water, power users, and conservation and 

recreation groups. Through extensive outreach 

efforts, the interested parties were engaged 

and their input was considered. This broad 

participation and input was 

critical to the Study. 

Because of the inherent complexities of the 

Study and the many diverse interests and 

perspectives, eight interim reports and 

technical updates were published to reflect 

technical developments and the ongoing input 

of stakeholders. The final documentation for 

the Study is organized into three major parts: 

this Executive Summary, a Study Report, and 

seven Technical Reports. A compact disc 

containing the Study documents in their 

entirety can be found inside the back cover of 

the printed report. 

Project participants and stakeholders are 

encouraged to comment on the information 

provided in the Study Report and associated 

Technical Reports. Comments received before 

April 19, 2013, will be summarized and posted to the Study website and may inform 

future planning activities in the Basin. 

Instructions for submitting comments are also 

provided on the Study website at: 

http://www.usbr.gov/lc/region/programs/ 

crbstudy.html. 

Recreation boating on Lake Powell in Utah 

5 
1.0	 Projected Future Water 

Supply and Demand 

Scenarios 

The amount of water available and changes in 

the demand for water throughout the Basin 

over the next 50 years are highly uncertain 

and depend on a number of factors. The 

potential impacts of future climate change 

and variability further contribute to these 

uncertainties. Nevertheless, projections of 

future water supply and demand were needed 

to assess the reliability of the Colorado River 

system to meet Basin resource needs and to 

identify options and strategies to mitigate 

future risks to those resources. To be 

beneficial, these projections had to be 

sufficiently broad to capture the plausible 

ranges of uncertainty in future water supply 

and demand. A scenario planning process was 

used to guide the development of scenarios 

that provided a broad range of projections, 

resulting in four scenarios related to future 

water supply and six scenarios related to 

future water demand. 

1.1	 Water Supply Scenarios 

Since 2004, Reclamation has conducted a 

multi-faceted research and development 

programs to investigate and implement a 

variety of methods for projecting future 

streamflow for Colorado River planning 

studies. Based on this work and the 

information gathered in the scenario planning 

process, four water supply scenarios were 

quantified and analyzed. These scenarios are 

titled Observed Resampled, Paleo Resampled, 

Paleo Conditioned, and Downscaled General 

Circulation Model (GCM) Projected and are 

described as: 

•	 Observed Resampled: Future hydrologic 

trends and variability are similar to the 

past approximately100 years. 

•	 Paleo Resampled: Future hydrologic 

trends and variability are represented by 

reconstructions of streamflow for a much 

longer period in the past (nearly 1,250 

years) that show expanded variability. 

•	 Paleo Conditioned: Future hydrologic 

trends and variability are represented by a 

blend of the wet-dry states of the longer 

paleo reconstructed period (nearly 1,250 

years), but magnitudes are more similar to 

the observed period (about 100 years). 

6
 
Projected Future Water Supply and Demand Scenarios 

•	 Downscaled GCM Projected: Future 

climate will continue to warm with 

regional precipitation and temperature 

trends represented through an ensemble of 

112 future downscaled GCM projections. 

Under the Downscaled GCM Projected 

scenario, the median of the mean natural flow 

at Lees Ferry over the next 50 years is 

projected to decrease by approximately nine 

percent, along with a projected increase in 

both drought frequency and duration as 

compared to the observed historical and 

paleo-based scenarios. The range of this result 

varies amongst the individual GCM 

projections that comprise this scenario with 

some of the GCM projections showing a 

larger decrease in mean natural flow than nine 

percent while others showing an increase over 

the observed historical mean. Droughts7 

lasting 5 or more years are projected to occur 

50 percent of the time over the next 50 years. 

Projected changes in climate and hydrologic 

processes include continued warming across 

the Basin, a trend towards drying (although 

precipitation patterns continue to be spatially 

and temporally complex), increased 

evapotranspiration, and decreased snowpack 

as a higher percentage of precipitation falls as 

rain, rather than snow and warmer temperatures, causes earlier melt. 

The process of using GCM projections and 

hydrologic modeling to generate projections 

of future streamflow presents a number of 

uncertainties and reflects methodological 

choices made in the Study. For example, 

choices of different downscaling techniques 

or the selection of a different hydrologic 

model to determine streamflow would yield 

different results. Notwithstanding minor 

methodological and reporting differences, the 

results presented in this report are consistent 

with Reclamation’s report to Congress 

published in March 20118 in fulfillment of the 

requirements within Section (§) 9503 of the 

SECURE Water Subtitle of the Omnibus 

Public Land Management Act of 2009 (Public 

Law 111-11). 

Lees Ferry, Colorado River, Arizona 

1.2 Water Demand Scenarios 

Historically, Reclamation has considered a 

single projection of future demands in longterm Basin planning studies. The Study 

considered a range of projections of demand, 

7 For the purpose of the Study, a drought period occurs whenever the running 2-year average flow at Lees Ferry falls below 15.0
 

maf, the observed historical long-term mean.
 

8 Bureau of Reclamation, 2011. SECURE Water Act Section 9503(c) – Reclamation Climate Change and Water 2011. 


7 
Executive Summary 

developed through a scenario 

planning process, which is a 

significant and important 

advancement in long-term water planning in 

the Basin. These demands were based on data 

and information provided by the Basin States, 

tribes, federal agencies, and other water 

entitlement holders. Through the scenario 

planning process, the most critical uncertainties affecting future demand were identified 

(for example, changes in population and water 

use efficiency) and were combined into six 

scenarios, as follows: Current Projected (A), 

Slow Growth (B), Rapid Growth (C1 and C2), 

and Enhanced Environment (D1 and D2). 

Agricultural irrigation in Arizona 

Based on these scenarios, and factoring in 

both Mexico’s 1944 Treaty allotment and 

water loss due to evaporation and operations, 

the Colorado River demand for consumptive 

The Study considered a range of 

projections of demand, developed 

through a scenario planning process, 

which is a significant and important 

advancement in long-term water 

planning in the Basin. 

uses is projected to range between about 18.1 

maf under the Slow Growth (B) scenario and 

about 20.4 maf under the Rapid Growth (C1) 

scenario by 2060. The largest increase in 

demand is projected to be in the M&I category, due to population growth. Population 

within the Study Area is projected to increase 

from about 40 million in 2015 to between 

49.3 million under the Slow Growth (B) 

scenario and 76.5 million under the Rapid 

Growth (C1) scenario by 2060. Additionally, 

the water demand assessment confirmed that 

the Lower Division States have demand for 

Colorado River water beyond their 7.5 maf 

basic apportionment across all scenarios. 

Non-consumptive9 demands, such as those 

associated with uses for hydropower and 

recreation and ecological resources, were 

included through the development of system 

reliability metrics and were not quantified in 

the same manner as demand for consumptive 

uses. For example, non-consumptive flow 

targets supporting the environment and 

recreational activities were developed for 

several locations throughout the Basin. The 

impact on these resources was assessed across 

all combinations of supply and demand 

scenarios in the Study’s system reliability 

analysis. 

9 Non-consumptive use is defined as water used without diminishing available supply. 

8
 
2.0	 Projected Future Water 

Supply and Demand 

Imbalances 

The range of the projected future water supply 

and demand in the Basin, as determined 

through the scenario process, is shown 

conceptually in figure 2. Without additional 

Dry dock at Lake Mead in Nevada 

future water management actions, a wide 

range of future imbalances is plausible 

primarily due to the uncertainty in future 

water supply. Comparing the median of water 

supply projections against the median of the 

water demand projections (medians are 

indicated by the darker shading), the longterm projected imbalance in future supply and 

demand is about 3.2 maf by 2060. The 

imbalance, however, can be 

much greater (or less) under any 

one of the multiple plausible 

future supply and demand 

scenarios. The projected 

imbalance in figure 2 does not 

consider the effect of reservoir 

storage, which has and will 

continue to be used to meet 

Basin resource needs when 

demand exceeds supply. The 

potential impacts associated with 

these imbalances to Basin 

resources were assessed through 

modeling and use of system reliability metrics, which consider 

the effects of reservoir storage. 

9
 
Executive Summary 

FIGURE 2



1 Water use and demand include Mexico’s allotment and losses such as those due to reservoir evaporation, native vegetation, and 

operational inefficiencies. 

Historical Supply and Use1 and Projected Future Colorado River Basin Water Supply and Demand 

10


3.0	 Options and Strategies 

to Resolve Supply and 

Demand Imbalances 

The Basin States have made significant 

investments in developing other water 

resources and implementing programs and 

policies to balance current and future supplies 

with existing and future demands. Many of 

these efforts have resulted in solutions to past 

water management challenges and will 

continue to provide benefit to the system in 

meeting the challenges that lie ahead. 

To identify a broad range of additional 

potential options to resolve water supply and 

demand imbalances, input from Study 

participants, interested stakeholders, and the 

general public was solicited for consideration 

in the Study. The solicitation period was from 

November 2011 through February 2012, and 

those interested in submitting ideas were 

asked to complete and submit an option 

submittal form. During this period, over 150 

options were received and were organized 

into 4 groups: 1) those that increase Basin 

water supply (Increase Supply), 2) those that 

reduce Basin water demand (Reduce 

Demand), 3) those that focus on modifying 

operations (Modify Operations), and 4) those 

that focus primarily on Basin governance and 

mechanisms to facilitate option implementation (Governance and Implementation). 

Despite the submission of several options that 

may ultimately be considered too costly or 

technically infeasible, the Study explored 

a wide range of options with the goal of 

ensuring that all viable options were 

considered. 

From these broad groups, categories of 

options were developed, and each submitted 

option was assigned to one category based on 

its primary function. Recognizing that every 

option submitted could not undergo further 

evaluation due to time and resource 

constraints, representative options that 

spanned the range of the option categories 

were developed. About 30 representative 

options were developed to ensure the concepts 

embodied in each submitted option were 

reflected and were further evaluated. Many of 

the representative options were evaluated 

quantitatively, which entailed an assessment 

of cost, yield, and timing in addition to 

assignment of a rating (“A” through “E”) to 

14 other criteria, listed in table 1. 

11
 
Executive Summary 

Technical Environmental 

Technical Feasib ity

Implementation Risks

Lo g Term Viab ity

Operatio al Flexib t y

Permitting

Energy Need s

Energy Source

Other Environmental Factors

Social Other

Recreation

Policy

Lega l

Socioeco omics

Q antity of Yield

Timing

Cost 

Hydropower

Water Quality

TABLE 1 

Criteria Used to Evaluate Representative Options 

While many of the criteria were assigned a 

qualitative rating, the assessment of cost, 

quantity of yield, and timing entailed numeric 

estimates to facilitate the grouping of these 

options into portfolios and the modeling of 

those portfolios. Costs were computed as 

present day annualized capital, operating, and 

replacement cost per acre-foot of option yield. 

Yuma Desalting Plant, Arizona 

It should be noted that the assessment of these 

criteria was at an appraisal level and there are 

many associated uncertainties, especially with 

respect to estimates regarding costs and 

quantity of yield. A qualitative description 

was provided for representative options for 

which the criteria listed in table 1 were not 

suitable, such as those options in the 

Governance and Implementation group. A 

summary of the representative options within 

the Increase Supply, Reduce Demand, and 

Modify Operations groups and the cost, yield, 

and timing, and their inclusion in portfolios, 

where applicable, is provided in table 2. 

The Governance and Implementation group 

consists of ideas and suggestions related to 

three major categories: Water Management 

and Allocation, Tribal Water, and Data and 

Information. Most concepts related to Water 

Management and Allocation and Tribal 

Water have significant legal and policy 

12 
Options and Strategies to Resolve Supply and Demand Imbalances 

m C

R m

M M

R

A

m G

R m

Y w

R

m

C

W

m C m

R

m tat

G C 2 , 30 A

O

C

1 , A

O

M

A

A

A C

A C

w 1,000 Al

G w

C

750 Al

G w A

Y m A

600 Al

linat

Mu W w 1,50 Al

G W 4,200 C

W w 2,000 4 Al

Re

ment C

M

W

R w 5 7 C

Local S ply

Cont 7,500 No

No

No

C 2 2

M m 500 No

m C 400

We

M

Al

W

M m

b total

R

O

O o n

C e g

O o n m

C

Y

A

Y

Y O

1 0

TABLE 2 

Summary of Representative Options Including Cost, Timing, Potential Yield, and Inclusion in Portfolios 

13 
Executive Summary 

TABLE 2
 

M Water

C

0 5 - 40 1 ,

15 1,

0 5 - 15 1,

A

A

A

M Water

C

R

m

A

W

C

A

W

C

A

W

C

w

1 , 1 ,

w

C A

C

A

A

C C

C

, 0 10 1

C

C m C

C

R

C

R

C

, 0 2 0

W

S y e m

O

M f y

O

M

R

O

N/A 15

Wat

N/A 10 A C

C o f

w

2 ,

Wat

m

A

W

C

w

Water 0 5 - 15 1,

A O s 5,

R

O

O o n

C e g

O o n m

C

Y

A

Y Y O

Summary of Representative Options Including Cost, Timing, Potential Yield, and Inclusion in Portfolios 

14 
Options and Strategies to Resolve Supply and Demand Imbalances 

Table 2 Notes 

1 Among the more than 150 options submitted to Reclamation as responsive to the Plan of Study, additional 


importation of water supplies from various sources, including importation of water from the Snake and Columbia
 

River systems, were submitted to the Study. Such options were appropriately reflected in the Study, but did not
 

undergo additional analysis as part of a regional or river basin plan or any plan for a specific Federal water resource
 

project. The Study is not a regional or river basin plan or proposal or plan for any Federal water resource project.
 

2 The two agricultural water conservation representative options derive potential yield from similar measures and are
 

thus not additive.
 

3 Subtotal assumes 150,000 afy for the Modified Reservoir Operations representative option.
 

4 The values related to Upper Basin Banking reflected assumptions developed for modeling purposes. It was
 

assumed that bank water is generated through conservation; therefore, the potential yield of the bank is consistent
 

with the Upper Basin portion of agricultural and M&I conservation and energy water use efficiency.
 

5 Total does not account for several options that may be mutually exclusive due to regional integration limitations or
 

are dependent on the same supply.
 

Glen Canyon Dam, Arizona 

considerations and were included in the Study 

but were not assessed. Where appropriate, 

these concepts will require future discussions 

beyond the scope of the Study. Data and 

Information ideas recommended future data 

and tool development to support future planning activities in the Basin. 

When considering all options and all categories, the potential yield is approximately 5.7 

maf per year (mafy) by 2035 and more than 

11 mafy by 2060. However, not all options 

are equally feasible or reliable in the long 

term. Some options, such as imports into 

southern California via submarine pipelines, 

water bags, icebergs, or those related to 

watershed management (e.g. weather 

modification or dust control), have either 

significant technical feasibility challenges or 

significant questions regarding their reliability. Excluding options that rate low for these 

factors, the potential yield is reduced to 

approximately 3.7 mafy by 2035 and to 

approximately 7 mafy by 2060. 

Recognizing no single option will be 

sufficient to resolve future projected supply 

and demand imbalances, groups of options, 

called portfolios, were developed to reflect 

different adaptive strategies. Each portfolio 

consists of a unique combination of options 

that were considered to address Basin 

resource needs—for example, the water elevation in Lake Mead—that may exist under 

future combinations of supply and demand. 

Four portfolios were evaluated in the Study 

and represent a range of reasonable but different approaches for resolving future supply and 

demand imbalances. The portfolios are not 

intended to represent all possible strategies for 

grouping options. Further, the Study does not 

result in the selection of a particular portfolio 

or any one option from any portfolio. The 

15 
Po o o N m Po o o D o

P B w m

w m

P C w w

m w w m

P D m P B

P C

P A P B P C

Executive Summary 

objective of the portfolio 

analyses is to demonstrate the 

effectiveness of different 

strategies in resolving future supply and 

demand imbalances. 

Using the ratings associated with the criteria 

listed in table 1 to express certain preferences 

towards a future strategy resulted in two 

portfolios, Portfolio B and Portfolio C. Two 

other portfolios were then developed, 

Portfolio A and Portfolio D, to represent a 

highly inclusive strategy that includes all 

options in either Portfolio B or Portfolio C 

and a highly selective strategy that includes 

only options included in both Portfolio B and 

Portfolio C. The four portfolios considered in 

the Study are summarized in table 3. 

Portfolio B is based on a strategy that seeks 

long-term water supply reliability through 

implementation of options with high technical 

feasibility and long-term reliability. The 

strategy can be defined as seeking options 

with proven technology that, once in place, 

will produce reliable long-term yield. The 

strategy represents a low-risk strategy in the 

long term, but allows greater risk with respect 

to permitting and implementation. 

TABLE 3 

Study Portfolios 

Conservation landscaping in Arizona 

Portfolio C focuses on options that are 

technically feasible but also may have lower 

environmental impacts such as low energy 

needs, lower carbon energy sources, low 

permitting risk, and low impacts to other 

environmental factors. The strategy can be 

defined as one that prioritizes options providing long-term solutions that are flexible and 

seek to enhance ecological and recreational 

flows while minimizing the effects on other 

Basin resources. The strategy represents a 

low-risk strategy in the near term but allows 

greater risk with respect to long-term 

performance of conservation measures. 

16
 
4.0	 Evaluation of Options 

and Strategies to 

Resolve Supply and 

Demand Imbalances 

The evaluation of the effectiveness of the four 

portfolios at resolving future potential supply 

and demand imbalances consisted of the 

following: identifying the reliability of the 

system at meeting Basin resource needs under 

all future supply and demand scenarios 

without portfolios in place (termed “Baseline” 

system reliability); defining of vulnerable 

Southwestern willow flycatcher 

conditions—those stressing to Basin 

resources; and evaluating the effectiveness of 

portfolios as measured by their ability to 

improve system reliability and reduce 

vulnerabilities relative to the Baseline. The 

estimation of cost and other tradeoffs 

associated with implementing the four 

portfolios were also explored. 

The performance of Basin resources was 

measured through system reliability metrics 

(metrics). With broad stakeholder involvement, a comprehensive set of metrics that 

span six resource categories (Water Delivery, 

Electrical Power, Water Quality, Flood 

Control, Recreational, and Ecological 

Resources) was identified. From those 

metrics, levels reflecting vulnerability or 

resource risk were identified. The combination of a particular metric and the assumed 

level of risk are termed “vulnerability.” Two 

important vulnerabilities that provide an 

overall indication of system reliability are: 1) 

Lake Mead elevation dropping below 1,000 

feet above mean sea level (msl) in any month 

and 2) Lee Ferry deficit10, when the 10-year 

10 Article III(d) of the Colorado River Compact stipulates that the Upper Division States will not cause the flow of the river at the 

Lee Ferry Compact Point to be depleted below an aggregate of 75 maf for any period of 10 consecutive years. For the purpose of 

the Study, a Lee Ferry deficit is defined as the difference between 75 maf and the 10-year total flow arriving at Lee Ferry. 

17
 
Executive Summary 

running total flow at Lee 

Ferry, Arizona is less than 75 

maf. 

Baseline system reliability was modeled 

considering all combinations of the supply 

and demand scenarios. Additionally, two 

operational assumptions regarding Lake 

Powell and Lake Mead operations beyond the 

effective period of the Colorado River Interim 

Guidelines for Lower Basin Shortages and 

Coordinated Operation for Lake Powell and 

Lake Mead in 2026 were considered. Since 

each supply scenario has over 100 individual 

sequences, the Baseline system reliability is 

comprised of over 20,000 simulations. 

Despite the findings from the water demand 

assessment that the Lower Division States 

have demand for Colorado River water 

beyond their 7.5 maf basic apportionment, the 

Baseline system reliability assumes deliveries 

to the Lower Division States remain 

consistent with and within their basic 

apportionment. 

In summary, the Baseline analysis indicates 

that without action, it will become 

increasingly difficult for the system to meet 

Basin resource needs over the next 50 years. 

Future projected development of water 

supplies and increased consumptive use in the 

Upper Basin combined with potential 

reductions in future supply results in reduced 

volumes of water stored in system reservoirs. 

With lower water elevations in reservoirs, the 

needs for resources such as hydropower and 

shoreline recreation were less frequently 

satisfied, while water delivery shortages 

increased. Decreases in flows in key river 

tributaries have negative implications for 

flow-dependent resources such as boating 

recreation and river ecology. These findings 

fully support the need to develop and evaluate 

options and strategies to help resolve the 

water supply and demand imbalance. 

Green River below Flaming Gorge Dam, Utah 

Vulnerabilities for the latter period of the 

Study period (2041 through 2060) under 

Baseline conditions are summarized in 

table 4. 

The Baseline system reliability also reveals 

that many combinations of future water 

supply and demand result in management 

challenges. In fact, most combinations stress 

some Basin resources through 2060. In the 

near-term (2012 through 2026), water 

demands are similar across scenarios, and the 

largest factor affecting the system reliability 

is water supply. In the mid-term (2027 

through 2040), the demand for water is an 

increasingly important element in the 

reliability of the system, as are assumptions 

regarding the operations of Lakes Powell and 

Mead. In the long-term (2041 through 2060), 

the futures that consider the Downscaled 

GCM Projected water supply scenario, which 

incorporates projections of future climate, 

show a high inability to meet resource needs, 

regardless of the demand scenario and the 

operation of Lakes Powell and Mead. The 

first stage in the portfolio analysis revealed 

that when all options in the most inclusive 

portfolio (Portfolio A) are implemented 

immediately upon availability, and without 

meeting demand of the Lower Division States 

above 7.5 maf, plausible futures still exist in 

18 
R sou

Wate D ve

ctrical ower

Fl C ol 

Wate Q

R c r tion 

Ecological 

Syst m Vulne bility B seli lio A lio B lio C lio D

7% 2% % 3% 3% 

we asin ( ke M pool 

elevation below 1,000 f msl)

%% 3% % 5% 6% 

18% 

19% 

9% 1 0% 10% 11% 

42% 14% % 19% 20% 

1% 4% % 3% 34% 

0% 0% 0 % 0% 0% 

30% 14% % 17% 19% 

24% 11% 1 1% 12% 13% 

57% % % % %

38% 30% % % %

12% 4% % 7% 8% 

p e asin 

Fe eficit)

we asin G rati

(Lake M elevati

below 1,05 eet msl

p e asin G rati w

4,4 gigawatts per h p e

fo consecutive y rs)

Sa nity below arke m

(gr te meric criteria)

C lorado Rive oating days 

le than curr conditions 

with vari le hydrolog

k e owe horeli Faci ties 

(pool elevati less than 3,56

fee msl

ke M horeli Fac ties 

(p elevati less t 1,08

fee msl

C lorado Ri v Flow less than 

targeted flow conditi

ove m to vis Dam Flow 

R ction a n al flow cha

g r ter than 845 thous

acr e e

C itical Rive low 

Hoove a m greate

,0 ic eet pe seco

T m C R S m S m w w

A m P C

D w GCM P

Evaluation of Options and Strategies to Resolve Supply and Demand Imbalances 

which the system is vulnerable. While the 

implementation of these options results in a 

sizeable reduction in vulnerability (the 

percentage of futures resulting in Lake Mead 

elevations being less than 1,000 feet msl is 

reduced from about 19 percent to 3 percent), 

these results indicate that complete elimination of Basin vulnerability is not likely 

attainable. 

Because the Lower Division States have 

demand for Colorado River water above their 

7.5 maf basic apportionment, any Basin-wide 

strategy must take this into consideration. As 

such, the portfolio analysis was designed to 

TABLE 4 

not only implement options to 

reduce system vulnerability, but 

also to satisfy the Lower 

Division States’ demand above the 7.5 maf 

basic apportionment. Augmentation, reuse, 

and conservation (with and without transfers) 

were the only options included in the 

portfolio analysis that could be used to satisfy 

these demands. 

A summary of the system reliability results 

with the four portfolios in place is also 

summarized in table 4. Each portfolio was 

modeled under all future conditions that 

comprised the Baseline reliability, resulting in 

Summary of System Reliability Outcomes (Percent of Years Vulnerable) for Baseline and Portfolios for All 

Scenarios, 2041–2060 Period 

1 The salinity component of the Colorado River Simulation System as presently configured works only with direct observed and 

paleo-reconstructed data. As such, values reported do not include results from the Paleo Conditioned and the Downscaled GCM 

Projected scenario. 

19 
Executive Summary 

over 20,000 simulations for 

each portfolio. The portfolios 

were modeled such that 

options were implemented only when needed 

to address specific vulnerabilities, thus 

minimizing the investment simulated in the 

analysis. As shown in the table, inclusion of 

the portfolios was projected to improve the 

ability to meet Basin resources needs (i.e. 

reduce vulnerabilities). The vulnerabilities 

related to critical Upper Basin and Lower 

Basin water delivery metrics were reduced by 

50 percent or more. The results for metrics 

related to electrical power, water quality, 

recreation, and ecological resources 

indicate similar reductions in vulnerabilities. 

Only the metric related to flood control below 

Hoover Dam shows a slight increase in 

vulnerability due to the potential for higher 

reservoir storage (and higher likelihood of 

high release) when portfolios were included. 

Although these reductions in vulnerabilities 

are encouraging, vulnerabilities continue to be 

present under some conditions, even when 

every option was implemented as soon as it 

was assumed to be available. This result is 

primarily because of the hydrologic 

conditions driving those vulnerabilities. 

Statistical analysis was performed to 

determine the specific hydrologic conditions 

(e.g., droughts of a particular length) that 

tended to result in certain critical vulnerabilities (e.g., Lee Ferry deficit and Lake Mead 

elevation less than 1,000 feet msl). Under 

Baseline conditions, the potential for these 

critical vulnerabilities was found to be 

strongly correlated to long-term mean natural 

flows at Lees Ferry below the historical 

average of 15.0 maf and droughts of 8 years 

or greater in duration. 

Although the implementation of the portfolios 

does not completely eliminate the occurrence 

of such critical vulnerabilities, the portfolios 

are successful in significantly improving the 

resiliency of Basin resources to these vulnerable hydrologic conditions. With portfolios in 

place, the system is able achieve similar levels of reliability under more adverse hydrologic conditions. Specifically, with portfolios 

in place, the long-term average flow to which 

the Basin is vulnerable is about 0.5 mafy less 

and the magnitude of the 8-year period of 

lowest flows is increased about 1 mafy. This 

type of information provides insight into specific hydrologic conditions that the system 

should be able to successfully endure and can 

inform water managers when crafting strategies to effectively hedge against those events. 

Although the portfolio analysis successfully 

demonstrated that system reliability can be 

improved, it is not without significant cost 

and performance tradeoffs. Figure 3 illustrates 

the performance across portfolios by water 

supply scenario in terms of addressing the 

critical Upper Basin and Lower Basin 

vulnerabilities. 

Portfolio B favors options believed to have 

higher certainty of available water supply 

once implemented. As shown on the right side 

figure 3, this portfolio performs as well or 

better than all the other portfolios for 

addressing the Lower Basin vulnerability. The 

portfolio is less effective than Portfolios A 

and C for the Upper Basin vulnerability 

(figure 3, left side), particularly in the 

Downscaled GCM Projected supply scenario 

(bottom row). 

Portfolio C, while focused on options 

that favor lower energy needs and less 

environmental impacts, is more dependent on 

shifting social values towards additional water 

conservation and reuse. Choosing to implement options characterized as having low 

20 
10% 20% 30% 40% 50% 10% 20% 30% 40% 50%

0 %

0 %

0 %

0 %

0 %

0 %

0 %

0 %

0 %

7 %

0 %

0 %

0 %

0 %

0 %

1 %

0 %

0 %

0 %

9 %

2 %

0 %

2 %

0 %

5 %

4 %

3 %

2 %

2 %

16%

11%

4 %

8 %

3 %

18%

18%

17%

11%

11%

44%

Portfolio B

Portfolio C

Portfolio D

Portfolio A

Portfolio

Baseline

Portfolio B

Portfolio C

Portfolio D

Portfolio A

Baseline

Portfolio B

Portfolio C

Portfolio D

Portfolio A

Baseline

Portfolio B

Portfolio C

Portfolio D

Portfolio A

Baseline

Percent Years Vulnerable Percent Years Vulnerable

Observed

Resampled

Water Supply

Scenario

Upper Basin Vulnerability

(Lee Ferry De!cit)

Lower Basin Vulnerability

(Lake Mead Pool Elevation

<1,000 feet msl)

Paleo Resampled

Paleo Conditioned

Downscaled GCM

Projected

Evaluation of Options and Strategies to Resolve Supply and Demand Imbalances 

FIGURE 3 

Percent of Years Vulnerable for Upper Basin (left) and Lower Basin (right) Vulnerabilities in 2041–2060 with 

Portfolios, by Water Supply Scenario 

energy needs (as a surrogate for potential 

environmental impacts) might come at the 

expense of having a less certain long-term 

water supply. However, this portfolio performs well for addressing the Upper Basin 

vulnerability (figure 3, left side) and is particularly effective under the Downscaled GCM 

Projected supply scenario (figure 3, bottom 

row). The effectiveness of this portfolio for 

addressing Upper Basin reliability vulnerabilities is largely attributable to the inclusion of 

an Upper Basin water bank that specifically 

targets this vulnerability. Portfolio C is less 

effective, however, at addressing the Lower 

Basin reliability vulnerabilities (figure 3, right 

side). 

Tradeoffs also exist with respect to portfolio 

costs, and these differ depending on the 

specific future conditions. As shown in figure 

4, the annual cost, in 2012 dollars, for 

implementing the portfolios ranges from 

approximately $2.5 billion to $3.5 billion in 

the year 2060 when considering the median of 

the Observed Resampled supply sequences, 

and from $3.6 billion to $5.8 billion when 

considering the median of the Downscaled 

GCM Projected supply sequences. The 

variability of the cost (reflected by the 

21 
2.0 3.0 4.0 5.0 6.0 7.0 2.0 3.0 4.0 5.0 6.0 7.0

%

0 %

0 %

30%

0 %

10%

20%

30%

0 %

10%

20%

30%

0 %

10%

20%

30%

0 %

10%

20%

30%

O

m

P t f Y

V l bl

P t f Y

V l bl

P t f Y

V l bl

P t f Y

V l bl

P t f Y

V l bl

w w

m w

w

M

m

w

M m

%

%

%

%

% %

%

%

%

%

Executive Summary 

FIGURE 4 

Portfolio Cost and Percent of Years Vulnerable for Upper Basin (left) and Lower Basin (right) Vulnerability for 

2041–2060 across Water Supply Scenarios and Lowest Streamflow Conditions 

1 Lowest Streamflow Conditions are defined as those in which the average of the 2012–2060 natural flow at Lees Ferry is less 

than 14 mafy and the lowest 8-year natural flow at Lees Ferry from 2012–2060 averages less than 11 mafy. 

22 
Evaluation of Options and Strategies to Resolve Supply and Demand Imbalances 

inter-quartile range or the length of the bars) 

reflects the varying size of the portfolios in 

different future conditions. Because of the 

appraisal-level option cost estimating used in 

the Study, the cost values contain additional 

uncertainty not directly reflected in these 

estimates. Across three supply scenarios 

(Observed Resampled, Paleo Resampled, and 

Paleo Conditioned), Portfolios B and D are 

generally shown to be less costly than 

Portfolios A and C. For the Downscaled GCM 

Projected water supply scenario tradeoffs 

between portfolios begin to become apparent. 

Specifically, Portfolio C leads to fewer 

vulnerable years with respect to Upper Basin 

vulnerability than Portfolios A and B, with an 

upper range of costs that is also lower than 

those for Portfolios A and B. Conversely, 

Portfolio A generally leads to the fewest 

vulnerable years with respect to Lower Basin 

reliability than other portfolios. 

The differences among the portfolios become 

more apparent in terms of costs and ability to 

reduce vulnerability as one focuses on the 

future conditions that are particularly 

stressing to the Basin. For water supply 

conditions that are less favorable, such as in 

the “Lowest Streamflow” subset of sequences 

(figure 4, bottom row), two distinct tradeoffs 

between reduction in vulnerability and cost 

across the portfolios are apparent. For the 

Upper Basin vulnerability, Portfolio C both 

performs better than Portfolios B and D in 

terms of reducing this vulnerability and has a 

lower range of costs than Portfolios A and B. 

For the Lower Basin vulnerability, however, 

Portfolio B reduces vulnerability more than 

Portfolios C and D and also results in lower 

costs than Portfolio A. 

Although the portfolios explored in the Study 

address water supply and demand imbalances 

differently, there are commonalities across the 

options implemented for each 

portfolio. All of the portfolios 

incorporate significant agricultural water conservation, M&I water conservation (1 maf each of both additional M&I 

and agricultural conservation was implemented in all portfolios), energy water use efficiency, and some levels of weather modification. However, some options were implemented more frequently in response to challenging 

water supply conditions. For example, ocean 

and brackish water desalination, wastewater 

reuse, and importation options were implemented for the most challenging water supply 

conditions in portfolios in which they were 

included. Future planning will require careful 

consideration of the timing, location, and 

magnitude of anticipated future Basin 

resource needs. The purpose of exploring 

these portfolios is not to identify a “best” 

portfolio or strategy, but to acknowledge that 

there are various ways to address the water 

supply and demand imbalance and to recognize that each approach has implications to be 

considered in future planning processes and 

decision-making. 

23 
5.0 Study Limitations 

Although the technical approach of the Study 

was based on the best science and information 

available, as with all studies, there were 

limitations. The detail at which results are 

reported or the depth to which analyses were 

performed in the Study was limited by the 

availability of data, assessment methods, and 

the capability of existing models. These 

limitations provide opportunities for additional research and development and the improvement of available data, which will be pursued 

in efforts independent of the Study. Notable 

Study limitations include the following: 

• Ability to Assess Impacts to Basin 

Resources – The ability to assess impacts to 

Basin resources, particularly in the Upper 

Basin, was limited by the spatial and temporal 

detail of the Colorado River Simulation 

System (CRSS), the primary model used in 

the Study. In particular, the Study’s assessment of water deliveries at local level, and 

ecological and recreational impacts were 

affected by these limitations. Future efforts 

will evaluate ways to improve the assessment 

of these resources in future studies which 

will include enhancements to CRSS, as 

appropriate. 

• Treatment of Lower Basin Tributaries – 

CRSS uses historical inflows (not natural 

flows) based on USGS streamflow records for 

four tributaries below Lees Ferry (the Paria, 

Little Colorado, Virgin, and Bill Williams 

rivers). In addition, the Gila River is not 

included in CRSS. The current treatment of 

these tributaries limited the ability of the 

Study to fully assess the natural supply of the 

Basin, and the data and methodological inconsistencies present in the Reclamation’s 

Consumptive Uses & Losses Reports limited 

the ability of the Study to gain a more 

complete understanding of historical 

consumptive use in the Basin. The Basin 

States will also work with Reclamation in 

Lake Powell, formed by Glen Canyon Dam 

24
 
Study Limitations 

fulfilling the commitments regarding the 

Lower Basin tributaries specifically described 

in Technical Report C – Water Demand 

Assessment, Appendix C11. 

• Treatment of Agricultural Land Use in 

Water Demand Scenarios – The development of the water demand storylines included 

participation from a broad range of stakeholders. The storylines were developed to represent a range of plausible futures regarding 

future demand. However, the assumptions in 

some storylines with regard to key driving 

forces resulted in the same directional 

changes in demand across the storylines. For 

example, the assumptions of continued conversion of agricultural land use to urban land 

use and lower-economic value crops being 

phased out in some areas led to overall agricultural land use (i.e., the number of irrigated 

acres) decreasing over time over all scenarios. 

Although some scenarios do show increasing 

agricultural land use at a state and local level, 

given recent projections of increased agricultural productivity necessary to meet future 

food needs, plausible futures should include 

increases in land use. 

• Option Characterization Process – The 

option characterization process strived for 

objectivity and consistency. The limitations 

identified during the characterization process 

included geographic limitations due to the 

extensive size of the basin and regional 

variety, the appraisal-level of the analysis, 

potential subjectivity during the characterization process, and significant uncertainty due 

to limited data. Specifically for those options 

associated with agricultural and M&I 

conservation and reuse, a detailed assessment 

by individual location for those options was 

not performed. Instead, these options were 

Bill Williams River, Arizona 

characterized at a Basin-wide level. The 

resulting assumptions were adopted for 

purposes of the Study and do not necessarily 

reflect achievable, or even desirable, local 

conservation goals for individual municipalities or agricultural locations. Further, not all 

stakeholders in the Study were in agreement 

with all characterization results, but recognized that future efforts beyond the Study 

should result in more in-depth assessments of 

the options and reduced uncertainty. 

• Consideration of Options – Due to the 

legal, regulatory, and sometime technical 

complexity of the options submitted, not all 

categories of options submitted underwent a 

quantitative assessment. As such, portfolios 

were largely limited to groups of options that 

lend themselves to modeling implementation 

within the Study’s timeframe, i.e. those that 

increase supply or reduce demand, with the 

exception of the Upper Basin water bank 

concept. The options modeled in CRSS do not 

necessarily reflect the entire range of innovative options and strategies that should continue to be explored in future efforts. 

25
 
6.0 Future Considerations Basin-wide levels is needed. The Study’s 

and Next Steps 

Colorado River water managers and 

stakeholders have long understood that 

growing demands on the Colorado River 

system, coupled with the potential for reduced 

supplies due to climate change may put water 

users and resources relying on the river at risk 

of prolonged water shortages in the future. 

The magnitude and timing of these risks 

differ spatially across the Basin. In particular, 

areas where demand is at or exceeds available 

supply are at greater risk than others. The 

Study builds on earlier work and is the next 

significant step in developing a comprehensive knowledge base and suite of tools and 

options that will be used to address the risks 

posed by imbalances between Colorado River 

water supply and resource needs in the Basin. 

The Study confirms that the Colorado River 

Basin faces a range of potential future 

imbalances between supply and demand. 

Addressing such imbalances will require 

diligent planning and cannot be resolved 

through any single approach or option. 

Instead, an approach that applies a wide 

variety of ideas at local, state, regional, and 

portfolio exploration demonstrated that 

implementation of a broad range of options 

can reduce Basin resource vulnerability and 

improve the system’s resiliency to dry 

hydrologic conditions while meeting 

increasing demands in the Basin and adjacent 

areas receiving Colorado River water. 

The Study confirms that the Colorado 

River Basin faces a range of 

potential future imbalances between 

supply and demand. Addressing 

such imbalances will require diligent 

planning and cannot be resolved 

through any single approach or 

option. 

The Study indicates that targeted investments 

in water conservation, reuse, and augmentation projects can improve the reliability and 

sustainability of the Colorado River system to 

meet current and future water needs. 

Ultimately, the Study is a call to action. To 

implement the water conservation, reuse, and 

augmentation projects identified in the Study, 

significant additional efforts are required 

immediately. These additional efforts, or next 

26
 
Future Considerations and Next Steps 

Deadhorse Point overlook, Colorado River in Utah 

steps, include a commitment to further 

analysis and planning in many areas related to 

the Study. 

In summary, there are several future actions 

that must take place to move closer towards 

implementing solutions to resolve imbalances 

in the Basin. First, significant uncertainties 

related to water conservation, reuse, water 

banking, and weather modification concepts 

must be resolved in order to adequately 

implement these approaches. Second, costs, 

permitting issues, and energy needs relating to 

large-capacity augmentation projects need to 

be identified and investigated through feasibility-level studies. Third, opportunities to 

advance and improve the resolution of future 

climate projections should be pursued and 

enhancements to the operational and planning 

tools used in the Colorado River system to 

better understand the vulnerabilities of the 

water-dependent uses, including environmental flows, should be explored. Fourth, as 

projects, policies, and programs are developed, consideration should be given to those 

that provide a wide-range of benefits to water 

users and healthy rivers for all users. 

In recognition of their ongoing joint commitment to future action, Reclamation will 

convene the Basin States along with tribes, 

other Colorado River water entitlement holders, conservation organizations, and other 

interested stakeholders in early 2013 to conduct a workshop to review the recommended 

next steps and initiate actions to implement 

next steps to resolve the current and potentially significant future imbalances in the 

Colorado River system. In early 2013 

Reclamation will also consult and work with 

tribes regarding tribal water issues reflected in 

this report. 

27
 
Executive Summary 

Disclaimer 

The Colorado River Basin Water Supply and Demand Study (Study) is funded jointly by the Bureau of 

Reclamation (Reclamation) and the seven Colorado River Basin States (Basin States). The purpose of 

the Study is to analyze water supply and demand imbalances throughout the Colorado River Basin and 

those adjacent areas of the Basin States that receive Colorado River water through 2060; and develop, 

assess, and evaluate options and strategies to address the current and projected imbalances. 

Reclamation and the Basin States intend that the Study will promote and facilitate cooperation and 

communication throughout the Basin regarding the reliability of the system to continue to meet Basin 

needs and the strategies that may be considered to ensure that reliability. Reclamation and the Basin 

States recognize the Study will have to be constrained by funding, timing, and technological and other 

limitations, which may present specific policy questions and issues, particularly related to modeling and 

interpretation of the provisions of the Law of the River during the course of the Study. In such cases, 

Reclamation and the Basin States will develop and incorporate assumptions to further complete the 

Study. Where possible, a range of assumptions will typically be used to identify the sensitivity of the 

results to those assumptions. 

Nothing in the Study, however, is intended for use against any Basin State, any federally recognized 

tribe, the Federal government or the Upper Colorado River Commission in administrative, judicial or 

other proceedings to evidence legal interpretations of the law of the river. As such, assumptions 

contained in the Study or any reports generated during the Study do not, and shall not, represent a legal 

position or interpretation by the Basin States, any federally recognized tribe, Federal government or 

Upper Colorado River Commission as it relates to the law of the river. Furthermore, nothing in the Study 

is intended to, nor shall the Study be construed so as to, interpret, diminish or modify the rights of any 

Basin State, any federally recognized tribe, the Federal government, or the Upper Colorado River 

Commission under federal or state law or administrative rule, regulation or guideline, including without 

limitation the Colorado River Compact, (45 Stat. 1057), the Upper Colorado River Basin Compact (63 

Stat. 31), the Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande, Treaty 

Between the United States of America and Mexico (Treaty Series 994, 59 Stat. 1219), the United 

States/Mexico agreement in Minute No. 242 of August 30, 1973, (Treaty Series 7708; 24 UST 1968) or 

Minute No. 314 of November 26, 2008, or Minute No. 318 of December 17, 2010, or Minute No. 319 of 

November 20, 2012, the Consolidated Decree entered by the Supreme Court of the United States in 

Arizona v. California (547 U.S 150 (2006)), the Boulder Canyon Project Act (45 Stat. 1057), the 

Boulder Canyon Project Adjustment Act (54 Stat. 774; 43 U.S.C. 618a), the Colorado River Storage 

Project Act of 1956 (70 Stat. 105; 43 U.S.C. 620), the Colorado River Basin Project Act of 1968 (82 

Stat. 885; 43 U.S.C. 1501), the Colorado River Basin Salinity Control Act (88 Stat. 266; 43 U.S.C. 

1951) as amended, the Hoover Power Plant Act of 1984 (98 Stat. 1333), the Colorado River Floodway 

Protection Act (100 Stat. 1129; 43 U.S.C. 1600), the Grand Canyon Protection Act of 1992 (Title XVIII 

of Public Law 102-575, 106 Stat. 4669), or the Hoover Power Allocation Act of 2011 (Public Law 112­

72). In addition, nothing in the Study is intended to, nor shall the Study be construed so as to, interpret, 

diminish or modify the rights of any federally recognized tribe, pursuant to Federal Court Decrees, State 

Court Decrees, treaties, agreements, executive orders and federal trust responsibility. Reclamation and 

the Basin States continue to recognize the entitlement and right of each State and any federally recognized tribe under existing law, to use and develop the water of the Colorado River system. 

28