WSP07709

• File Number: 8281.300
• Description: Colorado River Studies and Investigations -- Colorado River Consumptive Uses and Losses Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1977
• Title: Colorado River System Consumptive Uses and Losses Report -- 1971-1975
• Water Supply Pro - Doc Type: Report/Study

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tributary areas and into smaller subareas for
estimating and computational purposes. A suf-
ficient number of climatic stations are oper-
ated to!obtain the necessary temperature
and precipitation information required for the
evapotranspiration iormula. Research pro-
grams in developing techniques for automati-
cally identifying and measuring irrigated acre-
age through computer manipulation of satellite
digital data may ultimately aid in the as-
sessmen:t of cropped acreage. A weak link in
estimating the beneficial consumptive use by
agricultJre over broad areas is in assessing
the actu~1 water supply available, its adequacy
as a full ~upply, and its relationship to con-
sumptive, use.
Municipal, and Industrial: Most of the popula-
tion resid'ing within the boundaries of the
Lower Co/prado River system live in met-
ropolitanPhoenix, Tucson, and Las Vegas.
These cities and their surrounding environs
have the l)1utual problem of providing an
adequate ~urrent and future water supply for a
growing community in a water-short area. In
addition tQ an almost continuous flow of
studies cobcerning these problems, adequate
production: and effluent records are usually
available to adequately assess water use. Less
than 20 pJrcent of the total population. is
classified as rural having a significantly lesser
per capita ~se of water. In general, the rural
popUlation ~as considered to have a net .
water use rate of about 30 gallons per capita
per day. Consumptive use of water for ther-
mal power generation and the mineral resource
industries constitutes about 2.5 percent of
the total estiimated beneficial consumptive use
within the tf,ibutary areas. In general, infor-
mation rega~ding the annual use of water by
the mineral ~esource industry is inadequate.
The increasipg trend for recycling and the
methods of ~chieving compliance with quality
of water staridards are changing. Unit water-
quantity reqUirements for mineral production
and processibg may !lave been modified sig-
nificantly as compared to a decade ago.
Reservoir Evaporation: There are adequate
records avail~ble to estimate the annual
evaporation from the major reservoirs in the

tributary areas. Information on the fluctuation
of water levels in the smaller reservoirs and
stockponds is nearly nonexistent. Evapora-
tion from these smaller impoundments has
, been estimated on the basis of either "full"
or "average" capacity prevailing throughout
the year. Monitoring water-surface areas
through remote sensing techniques may rem-
edy this condition to some extent.

Beneficial Consumptive Uses and losses

Summaries of the Colorado River system
annual water uses, 1971-75, by States and
type of use are shown in tables C-2 through
C-6. Water use within the selected reporting
areas is discussed below.

UPPER COLORADO RIVER

Summaries of estimated annual consump-
tive uses and losses in the Upper Colorado
River Basin for each of the reporting years.,
broken down by State, reporting area, and
type of use are shown in tables UC-3 through
UC-7. Estimated main stem reservoir evap-
oration is shown in table UC-l.
Agriculturil' uses accounted for over 60
percent of the total Upper Basin consumptive
uses and losses. Irrigated acreage during the
5-year period averaged about 1,470,000
acres, with apparently little variation from year
to year. Irrigation consumptive use did, how-
ever, show large variations from year to year
due to climatic conditions. In 1971 and
1972, precipitation, temperature, and runoff
were at or slightly below normal over the Upper
Basin as a whole. In 1973, the basin experi-
enced exceptionally large amounts of precipita-
tion along with below-average temperatures.
This combination resulted in decreased irri-
gation needs. Conditions completely reversed
in 1974, when near drought conditions pre-
vailed over most of the basin. Irrigation re-
quirements that year were the highest of the
5-year reporting period. A large portion of the
irrigation requirement was met with carry-
over reservoir storage. As table UC-2
shows, major reservoir storage (excluding
main stem reservoirs) decreased in 1974 by

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