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CURECANTP~~ C~~ORADO RIVER STORA~ being more appropriate in view of the relatively minor amount of storage. The period ineludes the severely subnormal runoff period 1953-56, which was the most critical sequence of years from the stand- point of reservoir operations that has occured on the upper Gunnison River. The 1914-57 period also ineludes the 1914-30 period of above- average flows, the greatest drought decade of 1931-40, and 1954, the year of lowest recorded runoff on the uppcr Gunnison River. FUTURE UPSTREAM DEPLETIONS For this study it was assumed that no additional water use develop- ments upstream from the Gunnison tunnel would occur prior to 1970 since none of the authorized participating projects of the Colorado River storage project are located in the upper Gunnison River Basin. Five potential participltting projects in thltt bltsin, however, were men- tioned in the legislation authorizing the storage project as being among the projects to be givcn priority in future investiglttions and planning reports. These are the Tomichi Creek, East River, Ohio Creek, Fruit- land ~lesa, and Bostwick Park projects. Depletions from these pro- jects were assumed to bcgin in 1971 and increase uniformly until full dcplction is reltched in 2020. It was estimated that between 1 970 and 2020 average annual depictions would increase by 40,000 acre-feet above the Blue Mesa Dam site, by 50,000 acre-feet above the Morrow Point Dltm site, and by 60,000 acre-feet above the Crystal Dam site. After ~'ear 2020 no further additional depletions were anticipated. The annual depletions were assumed to vary slightly from year to year in accordance with the availltble water supply. A maximum average annual shortage of about 10 percent was assumed during the lO-year drought period, 1931-40. RESERVOIR LOSSES Streamflow depletions resulting from evaporation from the Cure- canti reservoirs are mq)eeted to average about 16,000 acre-feet annu- ally. Blue Mesa, being the largest reservoir, would sustain annual losses of about 14,000 aCl'e-feet as compared to 2,000 acre-feet at the Morrow Point Reservoir. Operation of Blue Mesa Reservoir for river regulation will result in significant fluctuations in reservoir content, surface area, and in water surface elevation. !\1onthly evaporation losses were computed for this reservoir at even lO-foot intervals of water surface elevation within the range of operation of the reservoir. The losses were derived from gross evaporation rates applied to the reservoir surface area from which were deducted present channel losses in the reservoir area and t.hat portion of the precipitation in the reservoir firea that is presently evaporated or transpired before it reaches runoff channels. Since :Morrow Point Reservoir \\~ll not fluctuate materially, constant annual evaporu.tion at this 1'eservoir was assumed. . Other reservoir losses, such as seepage and deep percolation, were assumed to be negligible at both reservoirs since the crystalline rock forming the dam foundations and lining much of the reservoir basins. is composed of massive igneous granite, gneiss, and schist. It is estimated that a reasonable grouting program \\~ll effectively seal any subsurface joints or fractures which may be discovered upon excava- tion of the dam foundations.