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{)OlM2 . . Draft Task 7 Technical Memorandum the model may often be artifacts of the aggregation of surface tributaries and return flows, review of these reaches helped identify potential low flow problems. This ex-post type of stream flow evaluation was helpful in determining whether additional instream flow requirements needed to be explicitly represented in the model. A minimum stream flow target in the Yampa River above the William Fork confluence is discussed further under Scenario V model assumptions. Meeting Demands Through Exchange The basin model allows demands located above storage supplies to be met by exchange. A water exchange allows an upstream junior to divert water out of priority in exchange for release from a downstream water replacement supply at some point above the downstream calling senior diversions. In the basin model exchanges occur automatically as the basin network is solved through the CRAM algorithm. SCENARIO I. NO ACTION (BASELINE) Key Assumptions of Scenario Scenario I attempted to represent physical conditions and water rights as they currently exist and are administered in the basin. This scenario was considered a No Action alternative. Three reservoirs were operated in this scenario including Stagecoach Reservoir, Steamboat Lake and Elkhead Reservoir. Operations of several other existing reservoirs in the basin, such as Lake Catamount, Yamcolo Reservoir and numerous small reservoirs, were not explicitly modeled. Depletive affects of these projects were considered either implicit in the gage-based model hydrology or, in the case of Lake Catamount, were modeled as a separate depletion. Reservoir Operations In Scenario I, access to reservoir storage by basin demands reflects contractual agreements with reservoir owners and operators. Demands within the Upper Yampa River Water Conservancy District (UYRWCD) may be met from storage in Stagecoach Reservoir. The Hayden Station is the only demand within the district which may be served from storage in Steamboat Lake, and then only after the Colorado Ute contract in Stagecoach has been fully depleted. Demands downstream of Hayden which are outside of the District, except for the Craig Station, have access only to storage in Elkhead Reservoir. Releases from Stagecoach were made to the Craig Station only after the Elkhead Reservoir power contract pool is empty. Storage contracts in reservoirs and control of which demands may access these contracts were controlled in the model by the use of relative ranking schemes. Excepting the Colorado Ute contract for the Craig Station, Stagecoach may not serve demands outside of the boundaries of the UYRWCD. Stagecoach Reservoir was modeled with four contract pools in this scenario including: . 9,000 af Colorado Ute (I'ri-State) . 4,000 af mixed use active storage . 3,635 af municipal and industrial . 16,640 af recreation (minimum pool) Releases from Stagecoach Reservoir can be made through an 109 cfs penstock or via an outlet works with a capacity of 450 cfs. As per requirements of the Federal Energy Regulation 7 .:1.; ,;<.