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<br />Study Methodology <br /> <br />This study compared the operation of the Colorado River Reservoirs <br />under a "no-strategy" base case with several alternative operating <br />strategies. In the base case, decisions to release water are based on <br />minimum water demands and adherence to minimum flood control require- <br />ments at Hoover Dam. At Glen Canyon Dam, base case decisions are <br />based on either the minimum objective releases (B.23 M~f) or storage <br />equalization provisions required by the Operating Criteria. <br /> <br />In alternative strategies, predictions and decisions are made on <br />October 1 to release surplus water at scheduled predetermined inter- <br />vals based on the probabilities of water supply. These scheduled <br />surplus releases increase immediate water availablity for project pur- <br />poses. At the same time, the system retains 602(a) storage to protect <br />against extended drawdown periods. <br /> <br />The alternatives were compared primarily using CRSS, Only general <br />findings, trends, and selective impacts are summarized here. Details <br />of the impacts on system storage, water deliveries, reservoir <br />releases, power generation, and other system parameters are presented <br />in the main report. <br /> <br />A complete description of the study process is also contained in the <br />main report. Study preparation involved updating the CRSS hydrology <br />data base through water year 1983. creating synthetic sets of hydro- <br />logic data (using a random number generator) to augment the historic <br />based set, updating and correcting the demand data base, and updating <br />system characteristics and modeling routines. <br /> <br />Key Study ~ssumptions <br /> <br />Use of CRSS Model <br /> <br />The CRSS was used to perform the simulations of the base case and four <br />alternative strategies. ~ general discussion of the model can be <br />found in the CRSS Executive Summary (October 1981) and more detailed <br />information is available in the CRSS System Overview (May 1985). <br /> <br />Two alternative depletion schedules and 17 hydrologic traces were <br />imposed on each of the five strategies. One run was required to evalu- <br />ate each depletion/hydrology/strategy combination; therefore, a total <br />of 17D runs (or 5 strategies x 2 depletion schedules x 17 hydrology <br />traces) were required to allow a complete comparison of all strate- <br />gies. Each run projected future demands for the IS-year period, 1985 <br />through 1999. <br /> <br />4 <br />