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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whereas the Colorado River Basin is
defined as; ....all of the drainage area of
the Colon(do River System and all other
territory within the United States of
America tQ which waters of the Colorado
River Sys~m shall be beneficially
applied." The compact divided the
Colorado River Basin into two
subbasinsHhe "Upper Basin" and the
"Lower Ba:sin," with Lee Ferry as the
division pOint on the river. Lee Ferry,
located in Arizona, is a point in the
main stem I mile below the mouth of
the Paria River. For the purpose of this
report, the Great Divide Basin, a closed
basin in Wyoming, and the White River,
also a closM basin, in Nevada have not
been consil!ered as part of the Colorado
River Systj!m since flows from these
basins nev,er reach the Colorado River.
Diversions; from the system to areas
outside its: drainage area are considered
herein as ~xports and have not been
classified by types of use.

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Beneficial 'consumptive use is normally
construed to mean the consumption of
water bro!jght about by human
endeavors 'and in this report includes
use of water for municipal, industrial,
agricultural, power generation, export,
recreation; fish and wildlife, and other
purposes, $long with the associated
losses incidental to these uses.

The storage of water and water in
transit may also act as losses on the
system although normally such water is
recoverable in time. Qualitatively, what
constitute. beneficial consumptive use is
fairly weU,understood; however, an
inability to exactly quantify these uses
has led to various differences of opinion.
The practil:al necessity of administering
the varioua water rights, apportion.
ments, etc!, of the Colorado River haS

j

led to definitions of consumptive use or
depletions generally in terms of "how it
shall be measured,' The Upper
Colorado River Basin Compact provides
that the Upper Colorado River
Co=ission is to determine the
apportionment made to each State by
....the inflow-outflow method in terms of
manmade depletions of the virgin flow
at Lee Ferry...." There is further
provision that the measurement method
can be changed by unanimous action of
the Commission. In contrast,
article leA) of the decree of the Supreme
Court of the United States in Arizona
vs. California defines, for the purpose of
the decree, "Consumptive use means
diversions from the stream less such
return flows thereto as are available for
consumptive use in the United States or
in satisfaction of the Mexican Treaty
obligation.' Nearly all the water
exported from the Upper Colorado River
System is measured; however, the
remaining beneficial consumptive use,
for the most part, must be estimated
using theoretical methods and
techniques. In the Lower Colorado
River System tributaries to the main
stem, similar methods must be employed
to determine the amount of water
consumptively used.

Reservoir evaporation loss is a
consumptive use associated with the
beneficial use of water for other
purposes, For the purpose of this
report, main stem reservoir evaporation
is carried as a separate item for the
Upper and Lower Basins.

Channel losses within the system are
normally construed to be the consump-
tive use by riparian vegetation along the
stream channel (or conveyance route)
and the evaporation from the stream's