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ll01313 . Draft Task 9 Technical Memorandum . Additional Model Refinements The following model refinements were imposed on all model runs described below. Reservoir Outlet Capacities The capacities of outlet works at Elkhead and Stagecoach Reservoirs were adjusted to reflect the enlarged reservoir sizes and the State Engineer's requirement for drawdown of 5 feet of head within 5 days time. For Elkhead Reservoir this translates into an outlet with a capacity of 655 cfs (the existing capacity of the outlet works at Elkhead is 250 cfs). The Stagecoach Reservoir outlet is modeled with a capacity of 450 cfs at the 33,275 af size and 605 cfs for the enlargement to 52,000 af. Elkhead Reservoir Minimum Release To reflect interests in establishing a tailwater fishery below Elkhead Reservoir a minimum release operation was imposed in the model. The reservoir was operated to release the minimum of inflow to the reservoir or 10 cfs. Recreation Pools at Elkhead and Stagecoach Reservoirs The recreation pool at the enlarged Elkhead Reservoir was defined according to previous specified requirements to constrain drawdown to a maximum of 10 feet during the summer months. When Elkhead Reservoir is enlarged to a capacity of 46,500 af, this translates to a recreation pool of 35,000 af during June, July and August. The recreation pool constraint at Stagecoach for both the existing and enlarged configuration is the same as the current recreation pool. Reservoir Starting Contents Previous modeling efforts had assumed that all reservoirs were filled to capacity at the beginning of the modeled study period. In Task 9 the starting contents of all reservoirs was set equal to the average end-of-month contents for September observed in the results from previous model runs. Stagecoach Reservoir was modeled with a starting contents of 31,000 af for the 2015 demand conditions and at 45,000 af under the 2040 demand conditions (with the enlargement to 52,000 af capacity). Steamboat Lake and Elkhead Reservoir were modeled with starting contents of 25,000 af and 35,000 af, respectively. Delivery of USFWS Supplemental Water The U.S. Fish and Wildlife Service has recently expressed interest in securing 5,000 af of water from the proposed Elkhead Reservoir enlargement to supplement low flows in the mainstem of the Yampa River at Juniper Canyon. This water would provide benefits to the habitat of the Threatened and Endangered fish. It is unclear precisely how the timing of these supplemental releases would be executed. It is likely that the USFWS would attempt to release the full 5,000 af each year while at the same time trying to make releases during the lowest flow periods of the year. Operation of these USFWS supplemental releases was implemented in the model. The amount of releases from the 5,000 af pool were determined through a pre-processing method. A minimum Juniper Canyon flow target was identified for each year of the study period that 9 ;1i....<-1