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<br />001314 <br /> <br />. <br /> <br />. <br /> <br />Draft Task 9 Technical Memorandum <br /> <br />could be met by releasing water from Elkhead Reservoir. This target was adjusted upward or <br />downward from year to year to ensure that the full 5,000 af was used in each year. This <br />minimum target ranged from 136 cfs to 467 cfs and averaged 274 cfs over the 53 year study <br />period. The model was not permitted to make these releases if to do so would violate the <br />Elkhead recreation pool. <br /> <br />The modeled strategy used to make supplemental water releases from Elkhead Reservoir <br />may not be the most productive in terms of optimizing habitat conditions of Threatened and <br />Endangered species in Juniper Canyon. For example, it might prove more beneficial to release <br />the entire 5,000 af during the same one or two month period of each year. However, the <br />supplemental releases as currently modeled, probably represent a reasonable approach in that it <br />is likely the releases would be made during different months each year as the need for <br />additional water became apparent. <br /> <br />Updated Model Results <br /> <br />Demand Shortages <br /> <br />Results of the revised model runs are presented in Tables 1 through 5. Table 1 <br />illustrates the shortages to demands under the 2015 demand conditions, I.e. with the <br />development of the 46,500 af Elkhead Reservoir. Shortages to the existing senior demands <br />averaged 18 af over the study period. Shortages to existing juniors and future junior demands <br />averaged 1,351 af per year and 164 af per year, respectively. Under 2040 demand conditions, <br />with only the enlargement at Elkhead Reservoir, future junior demands are shorted an average <br />of 4,793 af per year. <br /> <br />With the development of the Stagecoach Reservoir enlargement to 52,000 af, many of <br />the 2040 demand shortages are eliminated. While the minor shortages to the existing senior <br />demands remains the same as without the Stagecoach enlargement, the shortages to existing <br />juniors average only 31 af per year. Shortages to future (2040 level) juniors average 139 af <br />per year. . <br /> <br />Reservoir Contents <br /> <br />Figures 3 and 4 show reservoir contents over the study period. Under 2015 demand <br />conditions with only the enlargement of Elkhead Reservoir, Elkhead is drawn down an average <br />of approximately 10,000 af each year. The maximum drawdown typically occurs in the month <br />of February. Stagecoach Reservoir is drawndown each year due to hydropower operations in <br />an amount of approximately 7,000 af. Under 2015 demand conditions the storage in <br />Stagecoach is used infrequently. <br /> <br />In the long-term demand scenario (2040) that includes the enlargement of Stagecoach <br />Reservoir, Stagecoach is drawn down an average of 7,365 af per year as additional releases are <br />made out of its enlargement pool. Average maximum draw down of Elkhead Reservoir in this <br />scenario is approximately 17,000 af. <br /> <br />10 <br /> <br />. iit:;; :~"t <br />