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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Colorado Region'~ Comprehensive Framework
Studies. The sour~es of readily available and
published data ar~ essentially the same for
both reports. The report relies, in some
cases, on the results of special studies pre-
pared for the framework study.

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UPPER ~o.LORAOO RIVER
Irrigation Consumptive Use: Annual irrigated
acreage and croppihg patterns are the most
important items of bata required for a proper
determination of cd,nsumptive uses and
losses in the UpperiColorado River Basin. The
annual State agricu!tural statistics reports of
Wyoming, Colorado,; and New Mexico provide
good estimates of irrigated harvested cropland.
(This item of data is\not collected or reported
on in the Utah stati~tics report.) These data
are presented on a county basis and must be
disaggregated into tf,ibutary basins. Gener-
ally, this does not p1esent too much of a prob-
lem except in WyomIng, where county lines
and the Colorado River Basin divide are consid-
erably dissimilar. Mdre timely issuance of
the reports would beihelpful.
The determination pI irrigated nonhar-
vested cropland (mos~ly irrigated pasture
lands) is an area of ddta collection which needs
to be considerably st,J~ngthened. This item is
not reported on in thd State statistics reports.
The acreage used to d~velop the estimates of
irrigated pasture cons~mptive use for this
.
study are based very s;trongly on acreage val-
ues reported in the 1 Q69 National Census of
Agriculture. Other are~s of data collection
which need to be imprbved are (1) the deter-
mination of irrigated I~nds which receive less
than a full seasonal sURPly of irrigation water
and improvement of teChniques for estimat-
ing water use on these :Iands, and (2) up-to-
date inventories of seeped and phreatophyte
areas associated with irrigated lands. The pres-
ent level of climate dat~ acquisition is
adequate for the properiapplication of the
evapotranspiration formLla.

Reservoir Evaporation: The techniques and
data used to compute r~servoir evaporation
were generally satisfactqry. Of course, addi-
tional pan evaporation and reservoir content
records would strengthen the estimates.

Other Uses: The records of transbasin exports
and thermal powerplant uses are excellent.
The estimates of municipal and mineral re-
source uses could be enhanced through the
collection of additional diversion and return
flow records. However, extensive data acquisi-
tion programs for these items do not seem
warranted in light of their small magnitude in
comparison to the possible error of estimate
of the larger water-use items (e.g., irrigation,
evaporation).

LOWER COLORAOO RIVER ,

Mainstream: The annual land use, water supply,
and water use information being gathered for
the operation, maintenance, and administra-
tion of the Colorado River mainstream below
Lee Ferry is believed to be generally
adequate in quantity, quality, and extent.
Under more or less constant review, these
data are being continually upgraded wherever
deficient. Studies and programs are in prog-
ress to remedy a lack of data on return flows
from mainstream diversions and to correct
the apparent inaccuracies of the recorded re-
leases from Hoover Dam.

Tributaries: For the purpose of this report,
there are adequate data, for the most part, in
the tributary areas of the lower Colorado River
system to make reasonably accurate estimates
of the overall beneficial consumptive use of
water by the major types of use. Major uses
are agriculture, municipal and industrial, and
reservoir evaporation. Although most of the
data could be enhanced to some extent, up-
grading would entail the collection of supple-
menting data which would be both expensive
for fieldwork and instrumentation and for the
office work to assimilate these additional
data. Whether supplementing data would ac-
tually improve the accuracy of the net water
use must be carefully weighed, since most
theoretical techniques consider only a small
fraction of the factors involved.

Agriculture: County information is available
in most of the area to aid in the estimation of
irrigated crop acreage. In general, these data
are adequate although some difficulty is en-
countered in disaggregating the data into
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