WSP01965

• File Number: 8281.400
• Description: Colorado River Studies and Investigations -- Colorado River Depletion Projections
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/12/1969
• Title: Upper Basin Depletions
• Water Supply Pro - Doc Type: Report/Study

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period 1914-45. For the period after 1945 the differences are due primarily

to the manner in which the data was handled; although there are minor

differences in such items as changes in project reservoir contents and

transmountain diversion figures because, due to lack of records, a number

of these have had to be estimated.

The following summary table shows a comparison of 1968 modified

flows as computed by the USBR and the Type I study group.

Comparison of Data and 1968 Modified Flows
(based on 1914-:65 period)
Units: 1000 acre-feet

USBR Type I
(with salvage (w /0 salvage
effects) effects) Difference
Historic flows (avg) 12,426 12,426 0
Past consumptive use 2,218 2,448 230
Virgin flow (avg) 14,644 14,874 230
Present use (w /0 evap.
from Navajo's res.) 2,721 2,891* 170**
1968 modified flow 11,923 11,983 60**

* The Type I study shows a figure of 2808 for normalized uses as
of 1965 which included 31 for evaporation from Navajo reservoir. In order
for the Type I study to reflect 1968 uses on the same basis as the USBR
study it was necessary to subtract 31 and add 114 for increased uses be-
tween 1965 and 1968. (2808 - 31 + B4 = 2891)

** The Engineering Advisory Committee estimated 73,000 acre-feet
of salvage at Lee Ferry. If salvage were to be taken into account in the
Type I Study the difference in present depletions would be reduced to 97
and the difference in 1968 modified flows increased to 133. The USBR in
its CRSP studies allowed 115,000 acre-feet for salvage. On this basis
the difference in present depletions would be further reduced to 55.

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