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I I I I I I I I I I I I I I I I I I I 000442 Executive Summary August. A recreation pool of 16,400 af was defined at Stagecoach to be consistent with historical operating criteria. Although there is not a minimum release requirement below the existing Elkhead Darn, a minimum release of 10 cfs or inflow was defined in this Study for the enlarged reservoir. An existing release requirement below Stagecoach of the minimum of 40 cfs or the reservoir inflow was also represented. This Study defined the Juniper Project contemplated draft (adjusted to consider the drafts of existing reservoirs) as an instream flow right at Juniper . . Canyon. Water Supply Several model revisions and sensitivity tests were made which were designed to test the effects of various reservoir operating criteria imposed on the recommended enlargements. The final results of the revised model runs are presented in Tables S-6 through S-8. Table S-5 shows the shortages to demands under the 2015 and 2040 demand conditions with only the development of the 46,500 af Elkhead Reservoir. As shown in Table S-8, with the development of the Stagecoach Reservoir enlargement to 52,000 af, most of the 2040 demand shortages were eliminated. Table S-6 compares the water delivery shortages in these final model runs with those generated in Scenarios 1I1 and IV. As can be seen, the imposition of more specific minimum release and recreation pool operations at Elkhead had relatively little effect on modeled shortages. . Table 8-6 Comparison of Delivery shortages Between Initial and Final Model Runs Assuring Phased Enlargement of Reservoirs Demand Categorv Scenario 1I1 Scenario IV Final Runs Potential 1989 Maxirimm Average 5841 1955 n.a. 6595 1368 Projected 2015 Maximum Average 572 129 n.a. 572 164 Projected 2040 Maximum Average n.a. 5807 180 4040 139 Reservoir Water Levels Figures S-4 and S-5 show modeled reservoir contents over the study ,period for the 2015 and 2040 demand conditions, respectively. Under 2015 demand conditions with only the enlargement of Elkhead Reservoir, Elkhead was drawn down an average of approximately 10,000 af each year; this drawdown typically occurred in the month of February. Stagecoach Reservoir was drawn down each year due to hydropower operations in an arnount of approximately 7,000 af. Under 2015 demand conditions the storage in Stagecoach was used infrequently. S-21 ,. '!. ;-."