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

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

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

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

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 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?

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 ?????????

CURRENT WATER SUPPLY CONDITIONS

• 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 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 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

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??????????????