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- ..- " . rJ ~ {- ... c.. r . , . . test a variety of anticipated basin conditions and potential water markets. The model is discussed in greater detail in appendix 1 f:j! this report. Three operating scenarios were eXar.lined in this study. The first scenario assumed that the Upper Colorado River Basin Compact Call requiring.streamflow deliveries to lower basin States would be strictly administered. The Compact provides that the state of Colorado will not cause the flow of the Yampa River at the Maybell gaging stat~on to be depleted below an aggregate of 5 million acre-feet for any period of 10 consecutive years. (average of 500,000 af annually). -. The second scenario assumed that the Compact Call would not be administered or enforced. This scenario was operated to assess what impact (if any) the Compact eall (as operated in 1 above) has an annual yield of the Yampa River Reservoirs No.1 and No.2. . The third scenario was similar to the first except that the IO~ler basin deliveries were reduced from an average of 500,000 af/year to 100,000 af/year. This scenario was developed to test the sensitivity of the reservoir yields to varying compact quantities. ,. Inherent in all of the above operating scenarios were certain streamflow and reservoir operating assumptIons. These assumptions are shown below. Operational Assumptions, Yampa River Reservoirs No. '"and No.2, Yield Studies. .. 1. The total capacity of Reservoir No. 1 was operated at 1,082,00~ acre feet of which 942,000 af was active capacity. . 2. The total capacity "of Reservoir No. 2 was operated at 208,000 acre feet of which 190,000 af was ~ctive ~apacity. . " 3. Monthly evaporation losses were subtracted from end-of-month reservoir volumes. Reservoir evaporation (net) averages 32.5 inches annually. A reservoir volume-area relationship was" developed to calculate monthly evaporation losses from the reservoir surfaces as they fluctuated throughout the year. The reservoir evaporation losses would be offset in part, by reduced water use associated with the land that will be inundated by the reservoirs. These existing losses are attributed to evaporation from the river surface and evapotranspiration of non-beneficial phrcatophytes and irrigated hay and pasture crops adjacent the river. This will slightly increase the yield of the reservoir, hen-lever it was not within the scope of this study to quantify th; amount.