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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of irris-ation on the western slope and new works for transmountain
divers~ons have been constructed. The surplus available under
existing conditions is therefore materially less than it was when the
compact of 1948 was executed.

Irrigation in basin
The' Engineering Advisory Committee to the Upper Colorado
River Basin Compact Commission inventoried all the land under
irrigatipn on the western slope and also estimated the extent of other
areas on which water was consumed. It found that the total irri-
gated area was 790,600 acres, and that there were 106,800 acres more
on which water was consumed incidental to the practice of irrigation
on adja:cent areas.
. Recently the engineering research committee, which has been
advising the Colorado Conference Committee appointed by the
Colorado Water Conservation Board and which includes a number of
those on the original Engineering Advisory Committee to the Com-
pact Commission, has reviewed the prior estimates of irrigated lands
and oth'er lands consuming water. These revised estimates, which
are believed to reflect present conditions, are as follows:

Geographic unit

Irrigated Incidental
lands areas
(acres) (acres)
106, 115 19,444
285, 500 32, 903
254,737 32,915
85,862 10,250
91,858 11,300
824,072 106,812

Green Rlver~W"ampa River~Whlte River____~_~____~______~_____________.____
Colorado Rl~r, mam stem, exclusive of Gmmison River____________~______~
Gwmison River _ w _ _ _ __ _ _. ~ __ _ w_ ___ _ _ _ ____ _ _ ____ __ _ __ ,_ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __
Dolores River and lower tributaries of San Juan River __ __________________n
San Juan Rlv:()r above Shlprock_ _______________________~______~_____________

Total..._ __ __ _ _ _ __._. _ __ _._ _. _ _ _._ _. _. __ _ __._ _' ____ _ ___ _ _ _ _ ___ _ __ _ _ _.__

In the opinion of the engineering research committee, the depletion
at sites of use under present conditions amounts to 1,035,000 acre-feet
per year pn account of irrigation agriculture on the western slope.
This is an:increase of only 35,000 acre-feet above the average of deple-
tions for ~his cause during the period from 1914 to 1945.

Otherdeplttions with existing facilities
Much niore change in recent years has resulted from transmountain
diversions: The Colorado-Big Thompson project has practicalIy been
completed, and the delivery of water across the Continental Divide
through other facilities is now greater or could easily be greater than
the average of such diversions during the period from 1914 to 1945.
The total :depletions arising out of transmountain diversions with
existing facilities could be 388,200 acre-feet, including evaporation
losses from' reservoirs provided to make such diversions possible.
Domestic uses and other municipal and industrial uses have in-
creased somewhat in recent years and' there is now more water lost
by evaporation from reservoirs than when the detailed estimates were
made at the time of negotiation of the upper Colorado River Basin
compact. All such uses, however, amount to only about 10 percent
of the quantity now divertible across the mountains.

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60526-55-3

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