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<br />Executive Summary <br /> <br />modeled with a priority to fill ahead of the Juniper instream flow right. All basin demands had <br />access to water in the enlargement pool on a first-come, first-served basis. <br /> <br />Releases from the enlarged Ellchead Reservoir to satisfy demands were restricted by a <br />39,500 af minimum pool during the summer months, June, July and August. This feature of <br />the model was designed to reflect basin interests to maximize recreational potential of the <br />reservoir. <br /> <br />Scenario III model results revealed that shortages to existing senior demands were <br />unchanged in this scenario from the previous two scenarios. Shortages to existing junior <br />demands were substantially larger than in Scenario I but somewhat smaller than in Scenario II <br />because more storage water was available in Scenario III than in Scenario II. Existing junior <br />demands were shorted quite frequently, however. <br /> <br />Modeled shortages to the 2015 level demands were relatively small but shortages at the <br />2040 demand level were large and frequent. Many of the shortages to future level demands <br />were located in the Craig area and were the result of deliveries out of Ellchead Reservoir being <br />limited by the 39,500 af summer recreation pool. Additional shortages continued to occur due <br />to constraints of the outlet works capacity at Ellchead and Stagecoach Reservoirs and due to <br />limitations on access by some demands to contract storage at Stagecoach Reservoir. <br /> <br />Scenario IV - Enlargement of Elkhead and Stagecoach Reservoirs <br /> <br />Model runs in Scenario IV included both an enlarged Ellchead Reservoir and simulation <br />of an enlarged Stagecoach Reservoir. Ellchead reservoir was configured in exactly the same <br />way as in Scenario III. Stagecoach Reservoir was enlarged to a total capacity of 52,000 at <br />This represented an. increase in total storage of approximately 18,725 af over existing <br />conditions. The enlargement pool at Stagecoach was modeled in a manner similar to the <br />Ellchead enlargement in that the enlargement pool could be used by all demands on a first <br />come, first served basis. <br /> <br />Modeled shortages to existing senior demands remained unchanged from Scenario I, and <br />shortages to existing demands junior to 1954 were minor. Shortages to future level demands <br />were nearly eliminated by the extra water supply available in the Stagecoach enlargement. The <br />fact that some shortages occurred to existing junior demands but not to future junior demands <br />in this scenario is a result of the ability of contract storage to serve certain future demands. <br /> <br />- <br />In Scenario IV, all reservoirs remained nearly full throughout the study period, aside <br />from the seasonal operations of Stagecoach Reservoir and releases to supplement fish flows <br />from Steamboat Lake. The majority of the demands requiring storage releases were met out of <br />the Ellchead enlargement. There were no releases made to demands from contract storage in <br />Steamboat Lake. Augmentation releases from the enlargement pool in Stagecoach Reservoir <br />occurred when the outlet capacity of Elkhead Reservoir constrained releases there or when the <br />enlargement pool in Ellchead was inaccessible due to drawdown limitations for recreation. <br />Modeled shortages for Scenario IV are summarized in Table S-5. <br /> <br />Scenario V - Enlargement of Elkhead with Williams Fork Project <br /> <br />In Scenario V, a new storage project on the Williams Fork River was modeled along <br />with the Ellchead Reservoir enlargement. The Williams Fork Reservoir was modeled with a <br />70,000 af total capacity. Because the majority of basin demands are located above the <br />confluence of the Williams Fork with the Yampa River, Williams Fork Reservoir served <br />primarily as a source of exchange water. The exchange was used to satisfy downstream senior <br /> <br />S-21 <br />