The Colorado River and its Future

San Diego County Water Authority

Water Talks

May 1, 2012

The Colorado River and its Future Outline

• Background

• Coordinated operation of

Lake Powell and Lake

Mead

• Current state of the system

• Looking ahead

Colorado River Basin Background

7.5 maf

7.5 maf 2.8 maf

4.4 maf

0.3 maf

14 %

51.75 % 23 %

11.25 %

0.050 maf

1.5 maf

Summary Points:

• System is over-allocated

• Hydrology is highly variable and storage capacity is critical

• System is operated on a tight margin

Historical Colorado River Water Supply & Use

(Annual)

Major Upper

Basin

Reservoirs

Glen Canyon

Aspinall

Flaming Gorge

Navajo

Upper

Basin

Hoover Dam

Major Lower Basin Reservoirs

Davis Dam

Parker Dam

0%

10%

20%

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50%

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100%

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of

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January 1937 - March 2012

Lake Powell and Lake Mead Percent of Live Capacity

Mead Percent of Capacity Powell Percent of Capacity

During the 2000's drought, Lake Powell declined to elevation 3,555.1 ft, or 33% capacity, in April 2005

During the 2000's drought, Lake Mead declined to elevation 1,081.9 ft, or 38% capacity, in November 2010

Both reservoirs began WY 2000 at 95% capacity

Lake Mead began to fill in April 1936 and first filled to 100% capacity in July 1941

Lake Powell began to fill in June 1963 and first filled to 100% capacity in June 1980

During the 1950's drought, Lake Mead declined to a low elevation of 1,083.2 ft, or 40% capacity, in April 1956

Water Budget at Lake Mead

Inflow = 9.0 maf (release from Powell + side inflows)

Outflow = - 9.6 maf

(AZ, CA, NV, and Mexico delivery

+ downstream regulation and gains/losses)

Mead evaporation losses = - 0.6 maf

Balance = - 1.2 maf

Given basic apportionments in the Lower Basin, the allotment to Mexico, and an 8.23 maf release from Lake Powell, Lake Mead storage declines about 12 feet each year

Interim Guidelines for Operation of Lake

Powell and Lake Mead

• Key provisions:

– Operation for Lake Powell and Lake Mead is specified throughout the full range of operation

– Strategy for shortages in the Lower Basin is specified, including a provision for additional shortages if warranted

– Mechanism (Intentionally Created Surplus or ICS) is established to encourage efficient and flexible water use in the Lower Basin

• In place for an interim period (through 2026)

• Do not include provisions for Mexico

• ICS may be created through a variety of measures

• There is a 5% “system assessment” when ICS is created (except for system efficiency projects)

• ICS balance subject to 3% annual evaporation loss each year after creation

• Delivery of ICS may occur in years after creation

Intentionally Created Surplus (ICS)

Warren H. Brock Storage Reservoir

Colorado River Basin Storage (as of April 29, 2012)

Current Storage Percent

Full MAF

Elevation

(Feet)

Lake Powell 64% 15.51 3,636

Lake Mead 54% 14.00 1,124

Total System

Storage* 62% 37.19 NA

*Total system storage was 31.57 maf or 53% this time last year

2012 Upper

Colorado

Forecasted

Apr–Jul Inflow1 as of April 16

Flaming Gorge – 80%

Blue Mesa – 47%

Navajo – 57%

Lake Powell – 46%

1 Percent of average is based on the period of record from 1981-2010.

Water Year Snowpack and Precipitation as of April 30, 2012

Source: CBRFC

Chart developed with

Snotel data as of

4/30/2012

Colorado River

Basin above

Lake Powell

Water Year

Precipitation1

(year-to-date)

77%

Current

Snowpack1

29%

1 Percent of average is based on the period of record from 1971-2000.

State of the System (Water Years 1999-2012)1

109%

62% 59%

25%

52% 49%

104%

71% 70%

102%88%

73%

139%

61%

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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 2012 are projected. Unregulated inflow is based on the latest CBRFC forecast. Storage and percent capacity are based on the April 2012 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. Water years1999-2011 are based on the 30-year average from 1971 to 2000. Water year 2012 is based on the 30-year average from 1981-2010.

2

Historical and Projected Colorado River Water

Supply & Use

• Study Objectives

• Assess future water supply and demand imbalances through 2060

• Assess risks to basin resources

• Develop/evaluate options and strategies for resolving imbalances

• Email: ColoradoRiverBasinStudy@usbr.gov

• Website:

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

• A planning study – will not result in any decisions, but will provide the technical foundation for future activities

Colorado River Basin Water Supply and

Demand Study

The Colorado River and its

Future

For further information:

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