Colorado River Water Supply Colorado River Water Supply and 7 Stateand 7 State

Drought PlanDrought Plan

Don OstlerDon Ostler

Upper Colorado River CommissionUpper Colorado River Commission

The Colorado River Compact of The Colorado River Compact of 19221922

• Divides the River into an Upper and Lower Basin at Lee Ferry, Arizona

• Lower Division States – Az, Ca, Nv• Upper Division States – Co, NM, Ut, Wy• AZ, Nv, Ut and NM have lands in both basins• 242,000 square miles drainage area

• Serves the Basin & Cheyenne, Denver, Colo. Sprgs, Wasatch Front, Las Vegas, Phoenix, Tucson, Southern California, Albuquerque

Upper Colorado River Commission

Upper Colorado River Commission

1922 Colorado River Compact1922 Colorado River Compact

• Apportions 7,500,000 ac-ft/yr to both the Upper and Lower Basins

• Lower Basin given the right to increase consumptive use by 1,000,000 ac-ft/yr

Upper Colorado River Commission

1922 Colorado River Compact1922 Colorado River Compact

• Provides that Mexico be supplied with water, first from surplus over 16maf; and borne equally by the Upper and Lower Basins if no surplus

• Upper Basin shall not cause the flow at Lee Ferry to be depleted below 75,000,000 ac-ft for any ten years

Upper Colorado River Commission

The Mexican Treaty of 1944The Mexican Treaty of 1944

• Provides an annual delivery to Mexico of 1,500,000 ac–ft per year

• Provides an additional 200,000 ac-ft when there is a surplus

• Allows the USA to reduce deliveries during extraordinary drought in same proportion as USA uses are restricted

Upper Colorado River Commission

Upper Colorado River Basin Upper Colorado River Basin Compact of 1948Compact of 1948

• Division of Upper Basin water between states– 50,000 Ac-Ft to Arizona– 51.75% Colorado– 23.00% Utah– 14% Wyoming– 11.25% New Mexico

51.75% of 7.5MAF = 3.86 MAF/yr ??? Colo..

Is the water really there that was Is the water really there that was assumed by the 1922 compact assumed by the 1922 compact

drafters???drafters???

• How do their assumptions on available supply compare to the 100+ years of record???

• Should we rely on the current 100+ years of record?

Upper Colorado River Commission

Hydrologic DeterminationHydrologic Determination(Safe Annual Yield)(Safe Annual Yield)

• Upper Basin Safe Annual Yield = 6.04 MAF

• Upper Basin consumptive uses = 5.76 MAF (Colorado share = 2.95 MAF)

• Assumes a 6% chance of shortage

• 1922 Compact assumes 7.5 MAF/yr available ?????????

Upper Basin Consumptive Use

0

1000

2000

3000

4000

5000

6000

197119

7219

7319

7419

7519

7619

7719

7819

7919

8019

8119

8219

8319

8419

8519

8619

8719

8819

8919

9019

9119

9219

9319

9419

9519

9619

9719

9819

9920

00

Year

AF

x 1

00

0

Annual Water Consumed

Linear (Annual Water Consumed)

Source: Consumptive Uses and Losses Report - USDOI

Provided by: Eric Kuhn CRWCD

Upper Colorado River Commission

CURRENT WATER SUPPLY CURRENT WATER SUPPLY CONDITIONSCONDITIONS

– Major CRSP Reservoir Storage 6/30/06

• Reservoir Inflow % Storage%• Fontenelle 60 83• Flaming Gorge 54 83• Blue Mesa 53 97• Navajo 21 86• Lake Powell 53 52• Upper Basin Tot. 60

THE DROUGHTTHE DROUGHT

• 5 years of extreme drought (2000-2004)

• Unregulated inflows 62,59,25,51,49 %

• Powell fell to 33% capacity; 145 ft< full

• 2005 - 105% of ave. Powell + 31 feet

• 2006 – 73% of ave.

• Is the drought over???

Basin States Drought PlanBasin States Drought Plan

• Shortage plan for the lower basin– 200, 400, 600KAF shortage…..More??

• Coordinated operations of Powell and Mead– Equalization– Elevation targeted releases– Elevation targeted balancing of contents– Reduce curtailment and shortage risk

Basin States Drought PlanBasin States Drought Plan

• Improve system efficiency– Excess delivery to Mexico– More regulatory storage/canal lining

• Extraordinary Conservation – water bank– Fallowing farmland

• Augmentation projects– Desalination projects– Importation

Basin States Drought PlanBasin States Drought Plan

• Non-Colorado River system water exchange process– Non-Colorado River water provided to one

state in lieu of diverting Colo. R. water– Providing state allowed to increase their

diversion of Colo. R. water by same amount

• Accounting process

Questions of Science, Certainty, Questions of Science, Certainty, Risk, Politics and Urgency Risk, Politics and Urgency

• What amount of water should we plan on?

• What level of shortage risk shall we base our usage plan on?

• How do we use less precise forms of data in our water planning

• What weight do you assign to public acceptability of a plan?

Upper Colorado River Basin Upper Colorado River Basin Compact of 1948Compact of 1948

• Divides Upper Basin water between States– 50,000 ac-ft to Arizona– 51.75% to Colorado– 23.00% to Utah– 14.00% to Wyoming– 11.25% to New Mexico

51.75% of 7.5maf = 3.86 maf/yr ??? Colorado

Upper Colorado River Commission

Hydrologic DeterminationHydrologic Determination(Safe Annual Yield)(Safe Annual Yield)

• Upper Basin Safe Annual Yield = 6.04MAF

• Upper Basin Consumptive Uses = 5.76MAF (Colorado share = 2.95MAF)

• Assumes 6% chance of shortage

• 1922 Compact Assumed 7.5 MAF available??????????????