WSP08519

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1991
• Title: Colorado River System Consumptive Uses and Losses Report 1981 - 1985
• Water Supply Pro - Doc Type: Report/Study

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Coqsumptive Uses and Losses

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the basin as a whole. Reservoirs listed
in table UC-l are those to be charged to
the basin as a whole. These reservoir
evaporation losses amount to about
15 percent of all Upper Basin losses.

UpPer Basin consumptive use varied
between 3.9 million to 4.2 million and
averaged 4.0 million acre.feet per year
for the reporting period, 1981 through
1985. Agricultural uses accounted for
about 57 percent of the total Upper
Basin consumptive uses and losses.
Irrigated acreages fluctuated very little
during this period, ranging between
1,37 million acres to 1.45 million acres,
and1averaged 1.41 million acres per
yeat. Variation in consumptive use '
during the reporting period was largely
dueito year-to-year changes in climatic
conditions. '

~sbasin exports, the second largest
Upper Basin use, on the average
accqunted for 17 percent of basin use,
showed year by year variation during
the reporting period ranging from a high
of 820,OOOacre.feet in 1982 to a low of
577,000 acre-feet in 1983, Exports were
red~ced during 1983 and 1984 due to
recOrd amounts of winter precipitation
in the Rocky Mountain region, which
produced abundant water supplies on
the Front Range of Colorado, and in the
Great Basin of utah.

Water uses for thermal electric power
generation remained fairly constant,
averaging about 120,000 acre-feet per
year, which represents about 3 percent
of consumptive use in the Upper Basin.
Increases noted in past reports were
primarily due to new powerplants
coming on line, whereas there have been
no new power projects constructed
during this reporting period.

Lower Colorado River
Main Stem '$

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TableLC-l shows main stem reservoir
evaporation and apparent channel
losses, and table LC-3 shows water uses
along the lower Colorado River main
stem and flood plain including water
passing to Mexico. ' Water passing to
Mexico is made up of deliveries in
satisfaction of the Treaty, deliveries
made pursuant to Minute No. 242, Gila
River flood releases, regulatory waste
and anticipatory flood control releases
from the main stem. The latter three '
are combined as excess releases in
table LC-3 and for this reporting period
totaled slightly more than 37 million,
acre"feet. The previous 5-year reporting
period had identified excess releases to '
Mexico totaling about 5.4 million acre-
feet, with nearly 80 percent,~ this total
~. .
occurring in 1980 and corresPonding to
completion of initial filling of the Upper
Basin's Lake Powell.

Annual average main stem reservoir
evaporation consumed approximately
1.0 million acre-feet,

Transbasin diversions continued to be
the single highest consumer. For the
current reporting period, as for the
proceeding reporting period, transbasin
diversions continued to account for
approximately 72 percent of the Lower
Colorado River main stem depletions.

Lower Colorado River Tributaries

Tables LC-4 through LC.8 show annual
water uses within states by tributary
and type of use. Lower Basin
consumptive use was estimated to be
about 5.2 million acre-feet in 1981,