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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were credited to the irrigation water use
taken from the Article V report, and
were divided 'between California and
Arizona based on their respective
irrigation diversions.

Gross evaporation from Lake Mead is
estimated by 'the USGS and published in
its annual Water Resources Data
reports. Net 'evaporation for Lake Mead
is estimated by subtracting precipitation
at nearby BOlllder City,Nevada, (rom
the gross evaporation, Ne,t evaporation
from Lakes Mohe.ve and Havasu and
Senator Was~ Reservoir was derived
incorporating; Lake Mead gross'
evaporation and local precipitation
records and oPerating data,

Annual channel losses were estimated
as the inflow 'or outflow necessary to
balance a sim,plified water budget for
the Lee Ferry to Hoover Dam and
Hoover Dam to International Boundary
r,~aches. Channel losses include
evaporation, seepage, phreatophyte
consumptive 1,lSe. and bank storage. '

The accuracy 'of flow measurements of
the Colorado lUver mainstream for use
in determinin'g the channel losses values
in table LC-l1is in question. The gauge
error of an "excellent" USGS flow gauge
is 5 percent. !Actual flow at Lee Ferry,
Hoover Dam, 'or to Mexico may therefore
vary by 90,000 acre. feet for the low flow
entering Mexico in 1982 to over
'1,1 million acre.feet for 1984 flow below
Hoover. Sucn inaccuracies, though a
very small percent of total flow, will
have dramatic effects on apparent
channel loss Computations, as reflected
by channel gains.

The annual land use, water supply, and
water use information being gathered

for the operation, maintenance, and
administration of the Colorado River
main stem below Lee Ferry is believed
to be generally adequate in quantity,
quality, and extent. These data are
under constant review and are being
continually upgradeci Studies and
programs are in progress to remedy a
lack of data on return flows from main
stem diversions.

BENEFICIAL CONSUMPTIVE
USES AND LOSSES '

A summary table of the Colorado River
System total annual water uses, 1981
through 1985, by states and water
flowing to Mexico is shown on page iv.
Tables C-2 through C-6 show on a yearly
basis the same information broken down
by State, basin, and type of use. Water .
use within the ,selected reporting areas
is discussed below. .

Upper Colorado RIver
TrIbutarIes

Summaries of estimated annual
consumptive 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.2 through UC-6.

Estimated main stem reservoir
evaporation is shown in table UC-l.
Technically, these are not all main stem
reservoirs but are reservoirs that parti-
cipate in the Colorado River Storage
Project (CRSP). The Basin Commission
designates which,reservoirs in the CRSP
have evaporation losses charged to the
State and which have losses charged to

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