8013

• UCREFRP Catalog Number: 8013
• Author: Pontius, D. and I. SWCA.
• Title: Colorado River Basin Study.
• USFW Year: 1997.
• USFW - Doc Type: Tucson, Arizona.
• Copyright Material: NO

Colorado River Basin Study

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Table 2.-Estimated evaporative losses (1,000 acre-feet) from the Colorado River Basin
(1981-1985). These are the most recent estimates available from BOR
Year
State 1981 1982 1983 1984 1985 Average
Main stem1 1,598.4 1,402.9 1,896.2 1,197.1 1,782;9 1,575.5
Arizona 279.7 212.1 280.4 274.5 266.2 262.6
California 0.0 0.0 0.0 0.0 0.0 0.0
Colorado 82.7 78.4 82.3 84.2 86.3 82.8
Nevada 4.2 3.9 4.6 5.1 4.7 4.5
New 44.3 42.3 39.0 44.9 38.4 41.8
Mexico
Utah 65.0 59.4 63.0 64.7 69.0 64.2
Wyoming 41.6 39.2 36.7 34.5 30.5 36.5
Total 2,115.9 1,838.2 2,402.2 1,705.0 2,278.0 2,067.9
1 Main stem reservoir evaporation in Upper and lower Basins and main stem channel
losses for lower Basin.
Source: BOR, 1991.

the Colorado "hydrocommons" (Weatherford, 1994) and the total population
served is nearly 25 million people (Water Education Foundation, 1995).
Major out-of-basin diversions are depicted in Figure 5.

Major Water Use And Allocation

The Colorado River Compact of 1922 apportioned the use of 7.5 maf/year
each to the Upper Basin and Lower Basin, with an additional 1 maf allocated
to the Lower Basin.3 The 1944 Mexican Water Treaty guarantees delivery of
1.5 maf to Mexico, but provides for a pro rata reduction in times of shortages.
Under current conditions, demands on the river are much greater in the
Lower Basin. In 1996, the Lower Basin exceeded 7.5 maf of beneficial use

3 Article I1I(D) of the Compact requires that deliveries to the Lower Basin at Lee Ferry for
the current year plus the immediately preceding nine years (the ten-year moving average)
total no less than 75 maf.

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