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total or part of active reservoir storage used in each option. Proposed diversions for industrial and municipal use within the basin were assumed to be lOa-percent usage throughout the analysis; tbe proposed transmountain diversions also were varied by the same percentages as the proposed diversions for agricultural use. Agricultural Diversions Agricultural diversion for irrigation is one of the largest proposed uses of reservoir storage. An approximate monthly distribution of diversions, most occur- ring during the growing season, was assumed for all model simulations (table 2). The values shown in table 2 represent 100 percent of the agricultural irrigation water-~se allocations from the noted reservoir. For the analysis, it was assumed that the total active reservoir storage was available each year. In the model, it also was assumed that, of the monthly agricultural diversions, two-thirds would be returned to the streams and one-third would be lost--either by plant evapotranspi- ration or recharge to the ground-water system. Some agricultural diversion control-point locations are shown in figure 1, but because of the numerous return- flow sites, control points for return flows are not shown in figure 1. Industrial and Municipal Diversions Proposed industrial and municipal diversions used in the model are listed in table 4 and the corresponding control points are shown in figure 1; the values in table 4 were not varied during the model simulations. It was assumed that indus- trial diversions would be completely used in the cooling processes associated with electricity generation at fossil-fueled powerplants. Values for the amount of water needed for cooling per megawatt of electricity produced were adapted from computations by Palmer and others (1977). For example, in a wet-cooling tower, 27,000 acre-ft of water is required for every 2,000 megawatts of electricity gen- erated. For municipal uses, it was assumed that one-third of the diversions would be consumed and that two-thirds would be returned to the streams. Transmountain Diversions Two transmountain diversions from the Yampa River basin have been proposed: The Vidler diversion (Sheephorn project) that would divert about 132,000 acre-ft per year from the eastern part of the Yampa River subbasin to the Denver, Colo.t metropolitan area (Robert Moreland, Vidler Tunnel Corp., written commun., 1977) t and an addition to the existing Hog Park diversion that would divert a total of 31,000 acre-ft per year (23tOOO acre-ft per year addition to the 8,000 acre-ft per year present diversion) from the eastern part of the Little Snake River subbasin to Cheyenne, Wyo. (Banner & Associatest Inc., 1976). In the model, control point 39 (Yampa River at Steamboat Springs, Colo.) represents the withdrawal point for the Vidler diversiont which will divert water from the Yampa River and six tribu- taries upstream from Steamboat Springs, and control point 46 (Little Snake River near Slater, Wyo.) represents the withdrawal point for the expanded Hog Park di- version (fig. 1). The monthly schedules assumed for the diversions, which were based on the availability of water during peak-flow months, are listed in table 5. 12