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<br />~ <br /> <br />Affecting any plan of storage operations, of course, is the effect <br />of incoming sediment, which occupied a progressively greater portion <br />of the space intended for water storage. This is especially true of the <br />Colorado River, which is one of the streams most heavily laden with <br />sediment in the entire country. An encouraging report on this problem <br />is the conclusion of Gould (1954), that on the basis of studies of sediment <br />compaction and depositional slopes in Lake Mead, that that reservoir <br />can hold about 75 billion tons of sediment, which is 37 times the <br />accumulation in the first 14 years of the Lake. Thus the life of the <br />reservoir is now considered to be four or five centuries, even if no <br />intercepting facilities are developed upltream and naturally there are <br />several proposed sites for just that purpose. <br /> <br />.. <br /> <br />In addition to the sedimentation problem is also that of the effect <br />of evaporation upon storage. Whereas sediment is inimical to very <br />long-term storage, because it reduced the space needed for that storage, <br />evaporation is a handicap because it more immediately reduced the <br />amount of water then impounded. Obviously then, evaporation becomes <br />a limiting factor in the effective development of facilities for long-term <br />holdover storage of water. <br /> <br />In summary, it may be concluded that Lake Mead's effectiveness <br />in river regulation will diminish progressively unless supplemental <br />storage is provided for sediment. The maximum development and use <br />of water in the Upper and Lower basins combined must be less than the <br />long-term average flow of the river, however, because of the losses by <br />evaporation from the system necessary for supplying a stable operational <br />amount of water that will carry through the cyclic fluctuations in runoff. <br /> <br />Notation: Mr. Thomas elaborated on charts shown on the following <br />pages 4, 5, 6, 7, 8, 9, and 10. <br /> <br />******** <br /> <br />t <br /> <br />I <br /> <br />- 3 - <br />