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<br />. <br />r ' <br /> <br />, <br /> <br />c <br /> <br />To determine the amount of storage that could reasonably be available in a <br />critical drawdown period, several single-trace runs of trace 75 were made <br />until a level of demands was found that produced a drawdown in which the <br />system just emptied, i.e. reached minimum power pools or inactive storage <br />levels for one month. This occurred when the nominal demands reached a <br />level of 5.87 MAF in 2040. The run produced a drawdown that started with <br />the reservoirs full near the beginning of 2040 and just emptied in February <br />2065: This indicated a drawdown period of 25 years and 7 months. The <br />sediment-modified storage amq1.!nt utilized from filII system to empty, system <br />was 24.762 MAF. The actual depletions for the dr'awdown period inciuding <br />evaporation and adjustment for shortages amounting to 4.45 percent, <br />averaged 5.805 MAF. <br /> <br />tv <br />-..J <br /><:r.l <br />~-~ <br /> <br />Additional CRSS model runs were made to answer specific questions or allow <br />further analysis of some situations. A 100-year run of trace 75 was made <br />with the 8l-year hydrologic record being "wrapped around" to verify system <br />recovery. The run was identical to the previously discussed run through <br />the year 2066. The additional years of operation indicated that the system <br />would refill in June of 2072. <br /> <br />A trace 75 run was made with the surplus strategy turned-off. The surplus <br />strategy provides for the release of water early in a wet (above average) <br />year which would not normally be released until the flood runoff period. <br />The purpose of this strategy is to make better use of water in these higher <br />runoff years with the effect of drawing or keeping down reservoirs earlier <br />in the year. A run made with the surplus strategy turned-off was done to <br />answer questions regarding the effects of the surplus strategy. Although <br />the operation during the early years of the run varied somewhat, the system <br />filled and emptied in the same respective months as in the previous run. <br />Because the pattern of sediment deposition was changed somewhat, the <br />amount of water between full and empty states varied by about 15,000 acre <br />feet. When considered over the more than 25-year drawdown period this was <br />felt to be insignificant. <br /> <br />30 <br />