WSP11823

• File Number: 8281.400
• Description: Colorado River Studies and Investigations -- Colorado River Depletion Projections
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 3/25/1955
• Title: Report on Depletion of Surface Water Supplied of Colorado West of Continental Divide
• Water Supply Pro - Doc Type: Report/Study

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DEPLETION OF SURFACE WATER SUPPLIES

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would be at least $550 per acre and more likely would be as much as
$800 per acre. The Gunnison-Arkansas project, which might involve
the diversion of 500,000 acre-feet per year, would require subsidies
to irrigation of more than $1,000 per acre of all land benefited. .

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STORAGE REQUIRE'lV[ENTS

No large transmountain diversion can be made without the use of
a storage reservoir or reservoirs to impound the floodwaters which
would otherwise be unused in Oolorado. .
Such reservoirs will be needed for regulation of floods at or near
points of diversion to permit delivery of steady flows through the
tunnels and other conduits. A second and no less important function
of storage will be the maintenance of the natural flow of the streams
to the extent necessary to satisfy rights of others. .
Floodwaters may be impounded and diverted out of the drainage
basin of Oolorado River under present conditions without danger of
breach of the provisions of section (d) of Article III of the Oolorado
Ri'V'ffi' compact. The margin is not large, however, because during
the 10 years ending September 30,.1940, the total flow of Oolorado
River at Lee Ferry was only 101,510,000 acre-feet. Maintenance of
deliveries of 75 million acre-feet at this point in each consecJltive
10-year period will soon require storage to offset new depletions. It
follows that, when new depletions are made by transmountain diver.,
sions, reservoir capacity for cyclic regulation of the remaining flow
of Oolorado River will be provided in the proportion necessary. . .

OONCLUSIONS

We conclude from review of allavaiJable data and from independent
analyses that: .' . . .
. 1. All of the 7,500,000 acre-feet of water per annum apportioned tQ
the Upper Basin by the Oolorado River compact may not actually b~
available for use because of the requirement that 75 million acre-feet
be delivered at Lee Ferry during each consecutive 10-year period. .
2.0ompliance with this provision and limiting the carryover in
cyclic storage to the 22 years from 1930 to 1952 would have required
that reservoirs of 21 million acre-feet capacity had been available in
1927 for cyclic regulation and that the aggregate depletion in the upper
basin be no more than 6,200,000 acre-feet per year.
3. The total of all depletions at sites of use in Oolorado of the flow
of Oolorado River and its tributaries may thus be limited to 3,100,000
acre-feet per year.
4. Depletions in. Oolorado under present conditions aggregat~
practically 1,450,000 acre-feet per year.
5. Oommitments for extension of existing projects and for other
projects authorized would increase present depletions almost 200,000
acre-feet per year.
6. The present uncommitted surplus which can be relied upon for
use in Oolorado is thus 1,450,000 acr~feet per year. .
7. Development of the oil shale reserves in western Oolorado should.
be anticipated and the consumption of water for industrial, municipal,
and other purposes result,ing therefrom may reach 300,000 acre-feet.
per year.

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