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<br />Projected Plan of Operalion-
<br />Water Year 1981
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<br />CItrus Processmg Plant. Yuma, Ariz.
<br />
<br />Water Vear 1981
<br />At the meeting in Las Vegas, Nevada, on
<br />December 11, 1980, representatives of the
<br />seven basin states were advised that the
<br />active storage in Upper Basin Reservoirs
<br />on September 30, 1980, exceeded by
<br />more than 10 million acre-feet the require-
<br />ment for "602(a) Storage" as provided
<br />in the Colorado River Basin Project Act
<br />of 1968, and that Ihe Lake Mead storage
<br />credits that had accumulated to date
<br />would be extinguished and no further
<br />credits would be accumulated during
<br />water year 1981.
<br />
<br />Attendees at the Las Vegas meeting
<br />were invited to provide comments on
<br />the proposed operation plan for water
<br />year 1981 by January 31, 1981,
<br />
<br />After due consideration of all comments
<br />received and upon advice from the Sol-
<br />icitor for Interior, the Secretary deter-
<br />mined that the use of Lake Mead storage
<br />credits was not warranted after the
<br />filling of Lake Powell on June 22, 1980,
<br />Further deiiberations regarding the
<br />proposal to continue the use of storage
<br />credits led to the conclusion that the
<br />Secretary of the Interior could not allow
<br />the use of Lake Mead storage credits
<br />after Lake Powell Md filled because
<br />Section 602(a)(3)(ii) of Public Law 90-537
<br />requires that active storage in Lake Mead
<br />be maintained, as nearly as practicable,
<br />equal to Lake powell active storage,
<br />
<br />
<br />Aerial view looking north toward Imperial Dam
<br />
<br />The pian of operation for the Colorado
<br />River system that was implemented on
<br />October 1, 1980, and was presented at
<br />the meeting in Las Vegas on December 11,
<br />1980, was based on the amount of storage
<br />in the system at the beginning of water
<br />year 1981. The plan includes releases
<br />from Lake Poweli and Lake Mead being
<br />made in order to avoid anticipated flood-
<br />ing and spills to the extent consistent
<br />with maximum water conservatIon.
<br />
<br />Lake Powell is being operated to avoid
<br />anticipated spills and to equalize the
<br />ievels of Lake Powell and Lake Mead
<br />before December 31, 1981, Based on the
<br />newry instituted interim flood control
<br />agreement with the Corps of Engineers,
<br />releases from Lake Mead are being
<br />scheduled during the tall and winter
<br />months in anticipation of release require-
<br />ments for nood control in an average
<br />year. Based on current reservoir condi-
<br />tions and updated hydrologic forecasts,
<br />anticipatory releases from Lake Mead
<br />each month will be adjusted either up~
<br />wards or downwards as necessary to meet
<br />the objective of having full reservoir
<br />conditions by the time the Central Arizona
<br />Project (CAP) comes on line, These objec-
<br />tives are incorporated in the year's
<br />operating plan and are not intended as
<br />a modification of the current "long-range
<br />operating criteria" or to set a precedent
<br />as to how the system might be operated
<br />in future years.
<br />
<br />For average runoff conditions during
<br />water year 1981, the projected operation
<br />of each of the reservoirs in the Colorado
<br />River Basin are described in the following
<br />pages, Charts 1-8 show the projected
<br />monthly outflows from the reservoirs and
<br />the projected end-ot-month elevation and
<br />active storage in the reservoirs for average
<br />assumed runoff conditions and three other
<br />assumptions of moditied runoffs from the
<br />Basin for 1981. The four assumptions
<br />are (1) Average based on the 1906-79
<br />record runoff; (2) Upper quartile based
<br />on the annual level of annual streamflow
<br />which has been exceeded 25 percent of
<br />the time during 1906-79; (3) Lower quartile
<br />based on flows exceeded 75 percent of
<br />the time during 1906-79; (4) Most adverse
<br />based on the lowest year of record, which
<br />was 1977. The projected operations of
<br />Lake Mead reflect levels of antiCipatory
<br />releases for flood control during October
<br />through February and adjustments in
<br />actual releases for flood control during
<br />January through July that would result
<br />with the occurrence at the four assumed
<br />runoff conditions. The projected oper-
<br />ations of Lake Mohave and Lake Havasu
<br />also reflect the releases from Lake Mead
<br />resultll1g from system operations under
<br />these assumed runoff conditions.
<br />
<br />7
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