Colorado River Water Supply and 7 State Drought Plan Don Ostler Upper Colorado River Commission

The Colorado River Compact of 1922 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

1922 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 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 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 Compact 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 assumed by the 1922 compact 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 Determination (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 ?????????

Provided by: Eric Kuhn CRWCD Upper Colorado River Commission

CURRENT WATER SUPPLY CONDITIONS –Major CRSP Reservoir Storage 6/30/06 Reservoir Inflow %Storage% Fontenelle6083 Flaming Gorge5483 Blue Mesa5397 Navajo2186 Lake Powell5352 Upper Basin Tot. 60

THE DROUGHT 5 years of extreme drought ( ) Unregulated inflows 62,59,25,51,49 % Powell fell to 33% capacity; 145 ft< full % of ave. Powell + 31 feet 2006 – 73% of ave. Is the drought over???

Basin 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 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 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, 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 Compact 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 Determination (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??????????????