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<br />Executive Summary <br /> <br />rights. Existing demands with rights junior to the Juniper rights were served after existing <br />reservoirs reached their capacity. Future demand increments, representing either year 2015 or <br />year 2040 demands, were met after all other demand were met. In Scenario I, the Juniper <br />Project water rights were assumed not to exist; the same effect would obtain from the general <br />subordination of those rights. <br /> <br />Stagecoach Reservoir was operated to make winter releases for power generation; this <br />also assisted in making room for spring inflows. Steamboat Lake was also operated with <br />drawdown each year as a result of releases made to supplement flows in the Yampa River for <br />purposes of fish habitat. <br /> <br />In Scenario I, modeled demand shortages generally occurred only in the driest years and <br />then demands were met through releases from existing reservoirs. Some shortages were due to <br />capacity constraints of the reservoir outlet works. Other minor shortages occurred because the <br />modeled demands were located where it was impossible to increase the physical supply of <br />water, for example on small tributaries with no storage reservoirs. <br /> <br />Modeled shortages to future-level demands were also relatively small. Reservoir <br />releases made to mitigate shortages resulted in slightly increased fluctuations in reservoir <br />storage levels. Modeled shortages :ct the three levels of demand in Scenario I are summarized <br />in Table S-5. <br /> <br />Scenario II - Conversion of Juniper Rights Only <br /> <br />In Scenario II, a Juniper Canyon instream flow water right equal in magnitude to the <br />Juniper Project contemplated draft was modeled as existing with a 1954 priority date. The <br />amount of the contemplated draft was defined in an earlier study (Wheeler, 1989) and averages <br />862,000 af per year. As specified in this scenario, the instream flow right could not callout <br />the filling of existing reservoirs or the existing senior demands but could callout existing <br />junior demands and all future demands. <br /> <br />Modeled shortages to existing senior demands in Scenario II were identical to those <br />predicted in Scenario I. This was as expected since the instream flow right is junior to most <br />current level demands and should have no effect on them. Shortages to existing junior <br />demands were large as a result of these demands being called out nearly every year by the <br />Juniper instream flow right. Shortages to future demands under 2015 and 2040 demand <br />conditions, were also large and frequent. When the Juniper right was subordinated to all <br />junior demands, the previous shortages were reduced to Scenario I values. <br /> <br />In model runs which represented future demand levels, the Juniper-based instream flow <br />right frequently called out the junior future demand increments. This created a significant <br />draft on existing storage accounts to which the future demands have access. Ellchead Reservoir <br />(at its current capacity of 13,700 af) was drawn down to its minimum pool in most years. This <br />created numerous shortages to certain Craig area demands which were assumed to have no <br />access to storage in Stagecoach Reservoir. The modeled shortages at the three levels of <br />demand in Scenario II are summarized in Table S-5. <br /> <br />Scenario III . Enlargement of Elkhead Reservoir <br /> <br />Scenario III was similar to Scenario II in that it included the instream flow right at <br />Juniper Canyon, with a 1954 priority, but also included the simulation of an enlarged EI1<head <br />Reservoir. The enlarged Ellchead Reservoir was initially modeled with a total capacity of <br />52,000 af, representing an enlargement of 38,300 af. The enlargement pool (38,300 af) was <br /> <br />S-20 <br />