WSP02592

• File Number: 8221.107.J
• Description: Lower Colorado River Basin Project
• Basin: Colorado Mainstem
• Date: 11/1/1953
• Title: Memorandum Supplement to Report On Water Supply Of The Lower Colorado River Basin Project Planning Report - November 1952
• Water Supply Pro - Doc Type: Report/Study

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In general, allowances were made for these conditions by

assuming that annual depletions would vary from the average as

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one-half the deviation of the annual water supply from the

average water supply for the period of study.

1. Upper Colorado River Basin Depletions

Annual Upper Basin depletions of the flow of the Colorado

River at Lee Ferry were furnished by the regional office of

Region 4 of the Bureau of Reclamation. The depletions had been

varied annually as one-half the deviation of the annual virgin

flow of the Colorado River at Lee Ferry from the average.

Slight adjustments were made to confonn with differences in

rounding of the average estimates presented in the report of

the water supply of the Lower Colorado River Basin.

2. Lower Colorado River Basin Depletions

.
Annual variations in water uses, channel salvages, and

ground-water depletions were based on averages for the 1914-1945

period and the 1946-1951 period.

(a) Crops - The normal use of irrigation water by crops on

each irrigated area was determined for each year by applying unit

/

rates an acre computed from averages for the 1914-1945 period and

for the 1946-1951 period to the cropped acreages for each year in

the respective periods. The annual normal uses were adjusted by

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applying ~nnllal deviati911f'actors to derive estimates of the

actual annual consumptive use of irrigation water by crops in

each irrigated area.

The annual deviation factors ware based on the assumption that

the uses in anyone year would vary. from the normal use by a per-

centage equal to one-half the percentage variation of the water

supply in that year from the average water supply. The bases for