CRFS Technical MeetingLC Operations Update

November 16, 2010

Topics

• Operations Update– Summary 2010 – Projected 2011

• Probabilistic Mid-Term Operations Model

24-Month Study

ProjectedPowell

WY Unreg Inflow

ProjectedPowell Apr- Jul Unreg Inflow

ProjectedLake Powell

EOWY Elevation

w/ 8.23 maf Release

Projected Glen

Canyon WY

Release

Projected Amount of EQ

Release

ProjectedLake Mead EOWY

Elevation

Probability of EQ

Aug2009

91%11.0 maf

91%7.25 maf 3656.44 ft 10.49 maf 2.26 maf 1105.0 ft 70%

Sep2009

83%10.7 maf

91%7.25 maf 3652.70 ft 10.56 maf 2.33 maf 1105.0 ft 65%

Oct2009

83%10.0 maf

82%6.55 maf 3644.74 ft 10.59 maf 2.36 maf 1105.0 ft 55%

Nov2009

82%9.9 maf

82%6.55 maf 3644.33 ft 10.67 maf 2.44 maf 1105.0 ft 50%

Dec2009

82%9.9 maf

82%6.55 maf 3643.18 ft 10.77 maf 2.54 maf 1105.0 ft 36%

Summary of Lake Powell and Lake Mead OperationsReview of 24-Month Study 2010 Water Year Projections

In 2010, the Equalization Elevation was 3642 ft.

24-Month Study

ProjectedPowell

WY Unreg Inflow

ProjectedPowell Apr- Jul Unreg Inflow

ProjectedLake Powell

EOWY Elevation

w/ 8.23 maf Release

Projected Glen

Canyon WY

Release

Projected Amount of EQ

Release

ProjectedLake Mead EOWY

Elevation

Probability of EQ

Jan2010

77%9.3 maf

78%6.2 maf 3638.31 ft 8.23 maf 0.00 maf 1077.02 ft 21%

Feb 2010

73% 8.9 maf

73% 5.8 maf 3634.80 ft 8.23 maf 0.00 maf 1081.17 ft 25%

Mar 2010

69% 8.3 maf

68%5.4 maf 3631.88 ft 8.23 maf 0.00 maf 1081.36 ft 3%

Apr 2010

66% 8.0 maf

63%5.40 maf 3629.36 ft 8.23 maf 0.00 maf 1082.96 ft ---

Oct-12010

73%8.74 maf

73%5.79 maf 3633.66 ft 8.23474

maf 0.00 maf 1083.81 ft ---

Summary of Lake Powell and Lake Mead OperationsReview of 24-Month Study 2010 Water Year Projections

In 2010, the Equalization Elevation was 3642 ft.

895

3,642

3,575

3,370

1,22025.877 maf

0.0 maf

2.0 maf

Dead Storage

1.9 maf

Dead Storage

0.0 maf

9.5 maf

Lake Powell Lake Mead

Published April 2010 Projection for September 30, 2010

Equalization Elevation

3,70024.322 maf

Not to Scale

3617.60 Feet

1081.03 Feet

Apr-Jul Forecast =5.0 MAF(63% Average)

8.23 MAF

1,105 11.9 maf

End of Water Year 2010

Lake Mead elevation end of WY 2009: 1083.81 feet

• April 2010 24-Month Study projected end of WY elevation of 1081.03 feet

• Downstream water use during WY2010 lower than expected

• Due to winter storms and decreased irrigation demands, municipal users are conserving ICS credits in Lake Mead

Lower Basin Side InflowsGlen Canyon to Hoover in WY/CY 20101

Month in WY/CY 2010Total Glen Canyon

to Hoover(KAF)

Total Glen Canyonto Hoover

(% of Average2)

Difference From 5-Year Average

(KAF)

OBSERVED

October 2009 23 42% -32

November 2009 39 72% -15

December 2009 51 89% -6

January 2010 124 92% -11

February 2010 112 83% -23

March 2010 87 86% -14

April 2010 138 194% +67

May 2010 87 119% +14

June 2010 30 107% +2

July 2010 29 48% -32

August 2010 126 119% +20

September 2010 82 115% +11

October 2010 78 142% +23

HST

November 2010 54

December 2010 57

WY10 Totals 928 98% -19

CY10 Totals 1,004 106% +57

1Values were computed with the LC’s gain-loss model for the 24-month study2Percent of average was based on 5-year mean from 2005-2009

Water Year 2011 Projected Operations

• August 2010 Most Probable 24-Month Study projected Lake Mead elevation on Jan 1, 2010 to be 1086.38 feet

• ICS Surplus Condition to govern Lake Mead operations

• Mexico deliveries may be reduced

1,045

1,055

1,065

1,075

1,085

1,095

1,105

1,115

1,125

1,135

1,145

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Lake Mead End of Month ElevationProjections from October 2010 24-Month Study Inflow Scenarios

Historical Elevations

October 2010 Probable Minimum (9.00 maf release from Lake Powell in WY 2011)

October 2010 Most Probable (9.00 maf release from Lake Powell in WY 2011)

October 2010 Probable Maximum (13.45 maf release from Lake Powell in WY 2011)

The projected elevations in this graph are based on reservoir modeling under three possible inflow scenarios: 1) The minimum probable inflow scenario reflects a dry hydrologic condition which statistically would be exceeded 90% of the time; 2) the most probable inflow scenario reflects a median inflow condition which statistically would be exceeeded 50% of the time; and 3) the maximum probable inflow scenario reflects a wet hydrologic condition which statistically would be exceeded only 10% of the time. There is approximately an 80% probability that the future elevation will fall inside the shaded region. There are possible inflow scenarios that would result in reservoir elevations falling outside the range indicated in this graph.

Real Time Evaporation At Lake Mead

• 5-Year cooperative project with the USGS• Measure and obtain hourly evaporation

rates (and other parameters) from Lake Mead

• Develop new monthly coefficients for use in long-term modeling efforts

• Maintain program into the future

Comparison to Evaporation Rates in 24 Month Study

Month24-Month Study

Calculated Evaporation (KAF)

Measured Evaporation from

USGS (KAF)Difference (KAF)

February 2010 30 11 19

March 2010 33 20 13

April 2010 41 23 18

May 2010 47 33 14

June 2010 55 21 34

July 2010 68 30 38

August 2010 72 34 38

September 2010 59 32 27

October 2010 42 33 9

Impacts

• Will reduce error associated with 24-Month Study side inflow to Lake Mead term

• Since February, side inflows would have been lower than previously calculated

• Lower Basin is actively working with CBRFC to forecast side inflows as well

Development of New Probabilistic Mid-Term Operations Model• Motivation is to better quantify range of uncertainty

associated with mid-term operations forecasts• Being developed by CADSWES graduate student in

collaboration with Reclamation’s Modeling Work Group• Developed in parallel with the 24-Month Study model• Simulation horizon of 2-10 years• Input is range of probable inflows

– First and part of second year based on CBRFC’s ESP forecasts– On-going research to develop forecasting techniques beyond 2

years (being done by student developing model)• Results expressed in probabilistic terms• Target early 2011 for first version of completed model

Lower Colorado RiverOperations

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