The Colorado River:Operation, Current and Projected Future Conditions

Southern California Water DialogueLos Angeles, CAApril 27, 2011

Overview

• Basin Overview• Current System Conditions & Operations• Projected System Conditions

Colorado River Basin • 16.5 million acre-feet (maf)

allocated annually• 13 to 14.5 maf of

consumptive use annually• 15.0 maf average annual

“natural” inflow into Lake Powell over past 100 years

• Inflows are highly variable year-to-year

• 60 maf of storage

Historic Colorado River Water Supply & Use(Annual)

109%

62% 59%

25%52% 49%

104%

71% 70%

102%88%

73%

111%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

5

10

15

20

25

30

35

40

45

50

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Percent Capacity

Volu

me

in M

AF

End of Water Year

Unregulated Inflow into Lake PowellPowell-Mead Storage and Percent Capacity

Powell and Mead Storage (MAF) Unregulated Inflow into Powell (MAF) Powell and Mead Percent Capacity

1 Values for water year 2011 are projected. Unregulated inflow is based on the latest CBRFC forecast. Storage and percent capacity are based on the April 2011 24-Month Study. 2 Percentages at the top of the light blue bars represent percent of average unregulated inflow into Lake Powell for a given water year based on the 30-year average from 1971 to 2000.

2

Water Year Snowpack and Precipitationas of April 25, 2011

Colorado River Basin above Lake Powell

Water Year Precipitation

(year-to-date) 122%

Current Snowpack 130%

Chart developed with Snotel data as of

4/25/2011

Source: CBRFC

Lake Powell & Lake MeadOperational Diagrams and Current Conditions

4/24/111,096 11.14

4/24/11

4/24/113,611 12.79

4/24/11

April 2011 Results from CRSS Probabilities of occurrence, values in percent

Event or System Condition 2012 2013 2014 2015 2016

UpperBasin

Equalization release from Powell 48 46 50 40 41Balancing release from Powell 0 1 3 15 178.23 maf release from Powell 52 53 40 35 277.48 maf release from Powell 0 0 7 10 147.00 maf release from Powell 0 0 0 0 1

LowerBasin

Shortage – any amount (Mead ≤ 1,075) 0 0 2 16 20 Shortage – 1st level (Mead ≤ 1,075 and ≥ 1,050) 0 0 2 13 14

Shortage – 2nd level (Mead < 1,050 and ≥ 1,025) 0 0 0 3 6

Shortage – 3rd level (Mead < 1,025 ) 0 0 0 0 0

Surplus – any amount (Mead ≥ 1,145) 0 9 21 28 32 Surplus – Flood Control 0 0 3 4 7

Normal or ICS Surplus 100 91 77 56 48

Colorado River Basin Water Supply and Demand Study• Two-year, $2 million study cost shared by Reclamation

and the Basin States• Assess future water supply and demand imbalance over the

next 50 years• Assess risks to all Basin resources• Investigate options and strategies to mitigate impacts

• Study will identify and evaluate options, not at feasibility level

• A transparent, collaborative study with input from all stakeholders

• Email: ColoradoRiverBasinStudy@usbr.gov• Website: http://www.usbr.gov/lc/region/programs/ crbstudy.html

Addressing an Uncertain Future• The path of major influences on the Colorado River

system is uncertain and can not be represented by a single view

• An infinite number of plausible futures exist

• A manageable and informative number of scenarios are being developed to explore the broad range of futures

Scenario Funnel

Water Supply Scenarios *

Observed Resampled: future hydrologic trends and variability

will be similar to the past 100 yearsPaleo Resampled: future hydrologic trends and variability

are represented by the distant past (approximately 1250 years)

Paleo Conditioned: future hydrologic trends and variability

are represented by a blend of the wet dry states of the paleo-climate record but magnitudes are more similar to the observed period

Downscaled GCM Projected: future climate will continue to warm with

regional precipitation trends represented through an ensemble of future GCM projections

Water Demand Scenarios *

Current Trends: growth, development patterns, and

institutions continue along recent trendsEconomic Slowdown: low growth with emphasis on economic

efficiencyExpansive Growth: economic resurgence (population and

energy) and current preferences toward human and environmental values *

Enhanced Environment and Healthy Economy:

expanded environmental awareness and stewardship with growing economy*

* Additional “branches” possible depending upon assumed trajectory of specific socio-economic factors.

* Preliminary – Subject to change

The Colorado River:Operations and Current

Conditions

For further information:http://www.usbr.gov/lc/region

Driving Forces of Uncertainty

No. Driving Forces1 Changes in streamflow variability and trends2 Changes in climate variability and trends (e.g. temperature, precipitation, etc.)3 Changes in watershed conditions (e.g. diseases, species transitions, etc.)4 Changes in population and distribution5 Changes in agricultural land use (e.g. irrigated agricultural areas, crop mixes, etc.)6 Changes in urban land use (e.g. conversion, density, urbanization, etc.)7 Changes in public land use (e.g. forest practices, grazing, wilderness areas, etc.)8 Changes in agricultural water use efficiency9 Changes in municipal and industrial water use efficiency

10 Changes in institutional and regulatory conditions (e.g. laws, regulations, etc.)11 Changes to organization or management structures (e.g. state, federal, bi-national institutions)12 Changes in water needs for energy generation (e.g. solar, oil shale, thermal, nuclear, etc.)13 Changes in flow-dependent ecosystem needs for ESA-listed species14 Changes in other flow-dependent ecosystem needs15 Changes in social values affecting water use16 Changes in cost of energy affecting water availability and use17 Changes in water availability due to tribal water use and settlement of tribal water rights claims18 Changes in water quality including physical, biological, and chemical processes

Driving Forces Groupings

1

2

3

4

5

6

789

10

11

1213

14 15

16

1718

12

3

4

5

6

789

10

11

1213

14 15

16

1718

1

2

3

4

5

1 2 3 4 5

Unc

erta

inty

Importance

Uncertainty Impact Assessment - Toward Scenario Development(18 Driving Forces based on Expected Future Importance and Uncertainty)

Natural FlowColorado River at Lees Ferry Gaging Station, Arizona

Water Year 1906 to 2011

0

5

10

15

20

25

30

0

5

10

15

20

25

30

1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Annu

al F

low

(MAF

)

Water Year

Colorado River at Lees Ferry, AZ - Natural Flow

Average 10-yr Average

Provisional data, subject to change Estimated values for 2009-2011

• Seven years of unprecedented drought

• Increased water use• To date, there has never been a

shortage in the Lower Basin and there were no shortage guidelines

• Operations between Lake Powell and Lake Mead were coordinated only at the higher reservoir levels “equalization”

Impetus for the Interim Guidelines

Interim Guidelines1 - A Robust Solution

• Operations specified through the full range of operation for Lake Powell and Lake Mead

• Encourage efficient and flexible use and management of Colorado River water through the ICS mechanism

• Strategy for shortages in the Lower Basin, including a provision for additional shortages if warranted2

• In place for an interim period (through 2026) to gain valuable operational experience

• Basin States agree to consult before resorting to litigation

1. Issued in Record of Decision, dated December 13, 2007; available at http://www.usbr.gov/lc/region/programs/strategies.html

2. Mexico water deliveries are not directly affected by these guidelines

2011 Upper Colorado

Forecasted Apr–Jul Inflow

as of April 15

Flaming Gorge – 126%

Blue Mesa – 111%

Navajo – 70%

Lake Powell – 122%

Lower SNWA Intake1,000 ft

1,096 ft 11.14 maf(43% of Live Capacity)

895 ft Dead Pool Elevation

Lake Mead Capacity1,219.6 ft 25.9 maf

Dead Pool (2.0 maf)

Inactive Pool (7.5 maf)

Not to scale

124 ft

As of Apr 24, 2011

1,145 ft

46 ft1,075 ft

Shortage Conditions1,050 ft

Surplus Conditions

Normal or ICS Surplus Conditions

Min PowerPool

15.9 maf

1,000

1,025

1,050

1,075

1,100

1,125

1,150

1,175

1,200

1,225

Elev

atio

n (ft

)

January 1937 - March 2011

Lake Mead End of Month Elevation

Spillway Crest 1221 ft

March 201143% of Capacity

September 199995% of Capacity

Prior to 1999, Mead was last at elevation 1,096.39 feet during the filling of Lake Powell in May 1965.

In November 2010, Mead was at its lowest elevation of 1,081.94 feet since it was first filled in the late 1930s.

During the 1950s drought, Mead reached a low of 1,083.23 feet in April 1956.

3,400

3,450

3,500

3,550

3,600

3,650

3,700

Elev

atio

n (ft

)

January 1964 - March 2011

Lake Powell End of Month Elevation

March 201153% of Capacity

September 199995% of Capacity

Prior to 1999, Lake Powell was last at level 3,610.73 feet in May 1973.

Historic Colorado River Water Supply & Use(10-year Running Average)

Colorado River Basin Storage (as of April 24, 2011)

Current Storage Percent Full MAF Elevation

(Feet)

Lake Powell 53% 12.79 3,611

Lake Mead 43% 11.14 1,096

Total System Storage* 53% 31.46 NA

*Total system storage was 32.75 maf or 55% this time last year

Lower Basin Shortage through 2026

2010 2012 2014 2016 2018 2020 2022 2024 20260%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Probability of Shortage of Any AmountApril 2011 CRSS