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I I I I I I I I I I I I I I I I I I I OD2331 Executive Summary modeled with a priority to fill ahead of the Juniper instream flow right. All basin demands had access to water in the enlargement pool on a first-come, first-served basis. Releases from the enlarged Elkhead Reservoir to satisfy demands were restricted by a 39,500 af minimum pool during the summer months, June, July and August, This feature of the model was designed to reflect basin interests to maximize recreational potential of the reservoir, Scenario III model results revealed that shortages to existing senior demands were unchanged in this scenario from the previous two scenarios, Shortages to existing junior demands were substantially larger than in Scenario I but somewhat smaller than in Scenario II because more storage water was available in Scenario III than in Scenario II. Existing junior demands were shorted quite frequently, however, Modeled shortages to the 2015 level demands were relatively small but shortages at the 2040 demand level were large and frequent. Many of the shortages to future level demands were located in the Craig area and were the result of deliveries out of Elkhead Reservoir being limited by the 39,500 af summer recreation pool. Additional shortages continued to occur due to constraints of the outlet works capacity at Elkhead and Stagecoach Reservoirs and due to limitations on access by some demands to contract storage at Stagecoach Reservoir, Scenario I\( - Enlargement of Elkhead and Stagecoach Reservoirs \ Model runs in Scenario IV included both an enlarged Elkhead Reservoir and simulation of an enlarged Stagecoach Reservoir. Elkhead reservoir was configured in exactly the same way as in Scenario III, Stagecoach Reservoir was enlarged to a total capacity of 52,000 af. This represented an increase in total storage of approximately 18,725 af over existing conditions, The enlargement pool at Stagecoach was modeled in a manner similar to the Elkhead enlargement in that the enlargement pool could be used by all demands on a first come, first served basis. Modeled shortages to existing senior demands remained unchanged from Scenario I, and shortages to existing demands junior to 1954 were minor. Shortages to future level demands were nearly eliminated by the extra water supply available in the Stagecoach enlargement, The fact that some shortages occurred to existing junior demands but not to future junior demands in this scenario is a result of the ability of contract storage to serve certain future demands, In Scenario IV, all reservoirs remained nearly full throughout the study period, aside from the seasonal operations of Stagecoach Reservoir and releases to supplement fish flows from Steamboat Lake, The majority of the demands requiring storage releases were met out of the Elkhead enlargement. There were no releases made to demands from contract storage in Steamboat Lake, Augmentation releases from the enlargement pool in Stagecoach Reservoir occurred when the outlet capacity of Elkhead Reservoir constrained releases there or when the enlargement pool in Elkhead was inaccessible due to drawdown limitations for recreation, Modeled shortages for Scenario IV are summarized in Table S-5, Scenario V - Enlargement of Elkhead with Williams Fork Project In Scenario V, a new storage project on the Williams Fork River was modeled along with the Elkhead Reservoir enlargement. The Williams Fork Reservoir was modeled with a 70,000 af total capacity, Because the majority of basin demands are located above the confluence of the Williams Fork with the Yampa River, Williams Fork Reservoir served primarily as a source of exchange water. The exchange was used to satisfy downstream senior S,2l .'1;:,.]"