WSP03306

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1984
• Title: Colorado River System Consumptive Uses and Losses Report 1976 - 1980
• Water Supply Pro - Doc Type: Report/Study

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regulated releases from Lake Powell
at Glen Canyon Dam.
Annual reservoir evaporation
consumed between 1.0 and l.2 million
acre-feet. A~parent channel losses
ranged from 90;000 acre-feet in 1976
Oand 1977 to 430,,000 acre-feet in 1979.
," )Note that appar'ent channel losses were
W calculated over the entire Lee Ferry to
~ International Boundary reach instead
~ of only the Davis Dam to International
Boundary reach as in the 1971-75
report.
Total mainstream depletions de-
creased from 1976 to 1980, from 6.1 to
5.8 million acre-feet, with minimum
depletions of 5.7 million acre-feet in
1979. This 'reflects decreases of
140,000 acre-feet for irrigation
depletions and l30,OOO acre-feet for
exports to California from 1.976 to
1980. Depletions for irrigation in
1980 were 1.6 million acre-feet and
exports to Ca1;ifornia were 4.2 million
acre-feet the same year.
However, municipal and industrial
water use, including thermal power-
plants in Neva~a and Arizona, increased
depletions 1$ percent from 123,000
acre-feet to 150,000 acre-feet in the
5-year period. Much of this demand is
within the rapidly expanding population
area of southern Nevada.

Lower Colorado River Tributaries

Tables LC-4 through LC-8 show yearly
water uses by tributary area, State,
and type of use. Onsite consumptive
use in 1976 was estimated to be about
4.1 million acre-feet. By 1980,
consumptive use was about 4.8 million
acre-feet as a result of a. substantial
increase in both irrigated acreage and
population. Most of the increase in
water use, irrigated land, and popula-
tion has occurred in the Gila River
basin.

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Significant ground water usage
occurs in Arizona, Nevada, and New
Mexico. For the purpose of this
report, groundwater overdraft has not
been taken into account in the computa-
tion of tributary consumptive use.
Also tributary channel loss and
salvage were not evaluated. It should
be noted, however, that present ground
water overdraft in Arizona has been
estimated to be approximately 2.2
million acre-feet per year.
Consumptive use for the irrigation
of crops represents between 80 and 85
percent of the total water use in
the Lower Colorado tributary areas.
Estimated annual consumptive use per
area for the Lower Basin during the
5-year period averaged about 3.5
acre-feet per acre, varying from
approximately 1 acre-foot per acre in
parts of New Mexico to over 4 acre-feet
in the western portion of the basin.
Estimated crop consumptive use varied
considerably from year to year on the
basis of' climatic conditions, from a
low of 3.3 million acre-feet in 19~6 to
a high of 3.8 million Bcre-feet in
1980. Irrigated lands amounted to
1 ,067 ,000 acres in 1976, decreased
to l,037,OOO acres in 1978, and in-
creased to l,132,OOO acres in 1980.
The consumptive use of water for
municipal and industrial purposes is
estimated to have increased from
approximately 444,000 acre-feet in 1976
to approximately 500,000 acre-feet in
1980.
Water supply conditions were charac-
terized by near normal runoff in 1976,
exceptionally poor runoff in 1977, and
extremely large runoff in 1978, 1979,
and 1980. In addition tp replenishing
storage reservoirs in the basin, the
1978 through 1980 runoff produced an
outflow below Pai'nted Rock Dam of as
high as 2,385,000 acre-feet during
1980.

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