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<br />"" I. <br /> <br />Reservoirs above Lake Powell are modeled as single reservoir <br /> <br />Releases from reservoirs above Lake Powell follow rules of CRSS target <br />contents and powerplant schedules. <br /> <br />Reservoirs are adjusted for evaporation, sediment, and shoreline <br />bank storage <br /> <br />Lake Powell and Lake Mead equalization is computed using the 602(a) <br />storage requirement for the upper basin. <br /> <br />MODEL ASSUMPTIONS <br /> <br />BASIC MODEL CRITERIA NOT VARIED <br /> <br />602(a) Storage <br /> <br />Section 602(a) of Public Law 90-537 contains provisions for the storage of water in <br />reservoirs of the Colorado River Storage Project and for release of water from Lake Powell. <br />Generally, section 602(a) provides that water not required to be released from Lake Powell <br />as part of the annual objective minimum release shall be stored to assure future deliveries to <br />the Lower Division States without impairing annual consumptive uses in the Upper Division. <br />It further provides that water not required to be stored for this purpose shall be released from <br />Lake Powell to either maintain, as nearly as practicable, active storage in Lake Mead equal <br />to the active storage in Lake Powell, or to avoid anticipated powerplant bypass release from <br />Lake Powell. For long range planning purposes CRSS applies 602(a) using the critical <br />period of record as the controlling hydrograph. <br /> <br />Similar to CRSS the computation of 602(a) storage for CRSS-EZ modeling is dependent upon <br />five variables. <br /> <br />1. Assumes the critical period is the controlling hydrograph. <br /> <br />2. A verage annual flow at Lees Ferry for the critical period. <br /> <br />3. Percent shortage to be applied to the Upper Division scheduled <br />depletions for the purpose of computing 602(a) storage, if any. <br /> <br />4. Amount of power pool to be preserved in Upper Division reservoirs, <br />if any. <br /> <br />5. Estimated use in the upper basin for the critical period. <br /> <br />9 <br />