WSP06604

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/28/1989
• Title: Graphical comparison of the data contained in the BOR's Draft Colorado River System Consumptive Uses and Losses Report-- 1980-1985-- Part 1 of 2
• Water Supply Pro - Doc Type: Report/Study

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is that subsequent personnel have not been knowledgeable about portions of the
report prepared by or methodology used by their predecessors,

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Detailed consumptive uses and losses data have been provided by the Bureau of
Reclamation, but little to explain the methods used in compiling data for the
draft Uses and Losses Report has been included. A technical sununary should be
provided which explains the sources of data, and where appropriate, the methods
used for estimation,

Several of the project managers have indicated that representatives of the Upper
Basin States have been contacted and asked for estimates of various consumptive
use data in their States. Apparently, some data provided by the States has not
been included in the draft Uses and Losses Report. New Mexico representatives,
in particular, indicate that the information provided to the Bureau has been
largely ignored, or at least is not evident in the Report. If the data provided
by the States are not used, the Bureau should explain its methodology for
computing the data and the rationale for not using the data provided by the
States,

The draft Uses and Losses Report includes estimates of main-stem reservoir
evaporation. These data do not agree with the data provided by the Bureau of
Reclamation in the Status of Reservoir Reports, or the historical data on the
24-month studies, As an example, the following is a comparison of evaporation
from Lake Powell as listed in the draft Uses and Losses Report and Historical
data from the 24-Month Studies.

Comparison of Lake Powell Evaporation

\,later Year

1981

1982

1983

1984

1985

Average 1981-1985

Draft Uses 457.9
& Losses Report*

418.4

519.5

567.7

552,0

503.1

*
24-Month Study 583.0

575.0

628.0

619.0

615,0

604.0

*
Units 1,000 acre-feet

'Either the draft Uses and Losses Report or historical evaporation data is wrong.
The erroneous data should be identified and corrected.

The draft Uses and Losses Report does not report the lower basin main stem
channel losses. Page iv is a sununary of consumptive uses and losses in the
Colorado River System. It includes a line entitled "Other -- Reservoir
evaporation and channel loss;" however, the figures listed are sums of reservoir
evaporations contained on tables UC-l and LC-l, No estimates of channel losses
are included in these tables.

Since the time available to submit comments is limited, every effort should be
made to have finalized comments to the Bureau of Reclamation prior to the October
2, 1989 comment deadline.

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