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t 1 1 1 IJ I Reservoir Operating Studies 8,000 of/yr associated with operation of a coal-gasification plant in the Craig area. Given these data and assumptions, total annual basin depletions modeled under the 2015 and 2040 demand conditions are roughly 128,000 of and 159,000 af, respectively. Water Rights The water rights of the various demands are represented in the model only in terms of their priorities relative to each other and relative to the Juniper Project right. Generally speaking, existing uses are considered senior to the Juniper rights while future uses, both 2015 and 2040 level, are considered junior to the Juniper rights. There are two exceptions to this general rule: 1) certain existing agricultural uses are modeled as having rights junior to the Juniper project, and 2) the Hayden generating station has sufficient rights senior to the Juniper Project to serve its projected long-term demand. The model simulates the water rights and operations of three reservoirs, Stagecoach, Steamboat Lake, and Elkhead. At each reservoir the model simulates the administrative practices of the State Engineer. Storage water carried over on each reservoir's administration (or "start-fill") date is charged against the next year's decreed fill amount. The carryover water is charged against the senior-most decree first, then against the junior decrees. Although specific reservoir accounts are maintained throughout the water year, water carried over is re- allocated on the administration date among the various accounts according to specific account priorities. Reservoir administration dates were modeled as the first day of the month following the month having the lowest average simulated end-of-month storage. In all three cases the reservoirs were modeled with an administration date of April 1st. Three storage decrees were represented at Stagecoach Reservoir--the Stagecoach Reservoir decree for 22,106 of per year, the Bear Reservoir decree for 11,614 of per year, and the Four Counties decree which has an average annual limit of 4,595 af. The amount of the Four Counties decree varies from year to year depending on the natural yields of the rights at their original points of diversion on Fish and Walton Creeks in the upper Yampa River basin; for purposes of the basin model, this variable amount was determined by following a method described in a report prepared by W.W. Wheeler, Inc (1988). t u Two storage decrees are represented at Steamboat Lake, the original decree for 23,064 of and a new decree for 3,300 of applied for in 1993 by the Colorado Division of Wildlife (CDOW). The new decree permits the CDOW to legally store water above the present spillway crest at the lake; the supply so generated in the last few years has been leased under temporary contracts to the USFWS for mainstem flow enhancement. Three storage decrees were represented at Elkhead Reservoir in model scenarios representing the enlargement of the reservoir--the decrees for 8,310 of and 5,000 of associated with the existing reservoir and an additional decree reflecting the contemplated transfer of the River District's California Park Reservoir conditional water right to the enlarged reservoir. The California Park decrees include a first fill decree for 36,536 of having a 1972 priority and a refill decree for 35,026 of having a 1981 priority. For modeling purposes, only the first fill decree was assumed to be transferred to Elkhead. Table 2-2 lists the relative priorities of water rights and demands explicitly represented in various scenarios in the basin model. 2-5