Colorado River System Gross Number Analysis.do

• Title: Colorado River System Gross Number Analysis
• Date: 5/31/2007
• IBCC - Doc Type: Needs Assessment & Technical Support

Colorado River System Gross Number Analysis
(Updated 5/31/07)

Assulnptions
. Upper basin delivery obligation of 8.23 MAP at Lee's Ferry
o This is current DOl policy in the operations of Lake Powell. The Upper Basin
States dispute that they owe 750,000 affor Mexican Treaty obligations
o Question: Likelihood of a change in delivery obligations as a result of a policy
change or litigation?
. Reclamation's Hydrologic Determination of6,000,000 af
o This is based on 1954-1965 hydrology and excludes CRSP evaporation
o Question: Likelihood of the hydrologic determination changing?
. Colorado's current use of2,550,000
o This is based on DOl's Consumptive Use and Lose Report which includes CRSP
evaporation
o Question: Likelihood of this report being revised, especially with regards to
Colorado's irrigation use

COlnpact Entitlelnent
(7,500,000-50,000) x 0.5175 = 3,855,000 af/yr

Hydrologic Detennination (finn yield through a 1950's drought)
(6,000,000-50,000) x 0.5175 = 3,079,000 af/yr

Sensitivity Analysis
(% reduction in runoff due to clilnate change or recurring drought)
10% Reduction
(0.9 x 6,000,000 - 50,000) x 0.5175 = 2,768,625 af/yr

15% Reduction
(0.85 x 6,000,000 - 50,000) x 0.5175 = 2,613,375 af/yr

Colorado is currently using between 2.4 and 2.7 MAF/yr:
Average of2,550,000 af/yr