WSP01172

• File Number: 822.600.10
• Description: Colorado River Annual Operating Plan - Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1997
• Author: USDOI/BOR
• Title: Annual Operating Plan
• Water Supply Pro - Doc Type: Annual Report

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Lower Basin Reservoirs

Water shall be released or pumped from Lake Mead to meet the following requirements:

(a) 1944 Mexican Water Treaty obligations;
(b) Reasonable beneficial consumptive use requirements of mainstream users in
the Lower Division States;
(c) Net riverlosses;
(d) Net reservoir losses;
"(e) Regulatory wastes.

The Operating Criteria provide that after the commencement of delivery of mainstream water.
by means of the CAP, the Secretary of the Interior will determine the extent to which the
reasonable beneficial consumptive use requirement of mainstream users in the Lower
Division States is met. The reasonable beneficial consumptive use requirements are met
depending on whether a nonnal, surplus, or shortage condition has been determined. The
nonnal condition is defined as annual pumping and release from Lake Mead sufficient to
satisfy 9,251 MCM (7.500 MAP) of consumptive use in accordance with Article m(3)(a) of
the Operating Criteria and Article ll(B)(I) of the U.S. Supreme Court decree in Arizona V.
California. The surplus condition is defined as annual pumping and release from Lake Mead .
sufficient to satisfy in excess of9,25I MCM (7,500 MAP) of consumptive use in accordance
with Article m(3)(b) of the Operating Criteria and Article ll(B)(2) of the U.S. Supreme
Court decree in Arizona V. California.

While there is no agreed-upon surplus strategy, the most conservative strategy investigated in
preparing the 1997 AOP concerned the utilization of additional water in reservoir storage
resulting in the avoidance offload control releases at the 30 percent exceedance probability
of inflow to Lake Powell. This and other strategies seek to decrease the risk of flood control
releases from Hoover Dam, which allows increased beneficial use of water in the United
States. Possible impacts of a 1997 surplus determination were evaluated in terms of effects
on reservoir elevations and releases and increased risk of future shortages. This analysis
showed that the 1997 surplus determination will cause neither significant effects on reservoir
contents in Lakes Powell and Mead nor significant additional risk of future shortages in
Arizona.

The amount of additional mainstream water being made available during calendar year 1997
is limited to that quantity required to satisfy the reasonable beneficial consumptive use
requirements of Colorado River mainstream water users in the Lower Division States with
valid contracts or Federal or decreed entitlements. The making of this determination does not
preclude the Secretary from adopting other determination criteria in future years.
Furthermore neither this determination nor the basis on which it was made constitutes a
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precedent for future determinations.

Taking into account (I) the existing water storage conditions in the basin, (2) the most
probable near~tenn water supply conditions in the basin, and (3) that the benefi~al

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