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Show Dam carries about 1,500 second feet or 675,000 gallons per minute to various communities in the Los Angeles area. Because of the critical water supply situation in San Diego during World War II, an extension to this aqueduct was built to that city, carrying about 50 million gallons daily. The quality of the surface waters varies in differ- ent parts of the basin from the purity of melted snow to weak brines with dissolved content of 3,610 parts per million. The chemical character- istics of the main rivers of the basin vary from season to season. The majority of the waters con- tain about 200 parts per million dissolved solids and have a hardness of about 100 during the spring floods. The dissolved solids content increases as river flows drop, eventually reaching 500 to 1,200 parts per million, while the hardness increases to 300 to 400 parts per million. The mixing in Lake Mead of tlie relatively pure floodwaters with the highly mineralized low flow waters equalizes the quality downstream to a uniform hardness of about 350 parts per million and a dissolved solids content of about 660 throughout the year. Both surface and ground waters are considered suitable for all present uses, including public water supplies, except in a few localized areas. Control of natural pollution from silt and salt is the major problem. In the Phoenix area about 100,000 people dispose of their sewage through individual subsurface dis- posal systems. This practice undoubtedly pollutes shallow underground water which might some day be called upon to serve the needs of this rapidly growing community, although it is not used to any extent for present water supply. Most of the domestic sewage in the area either seeps into the ground or reaches irrigation ditches where it amigments the quantity and perhaps im- pairs the quality of both ground and surface domes- tic water supplies. Knowledge is needed of the effect of sexvage pollution on water supplies in this basin. Recreation The Present Situation The Colorado River Basin, with its Grand Can- yon and a great variety of other natural scenery, its areas o€ scientific interest, its present Indian, Spanish, and Anglo-American cultures, and its favorable climatic conditions, is one of the out- standing recreation regions in the United States. 376 The major outdoor activities related to water in the basin are: those related to the mountain streams, especially fishing; hunting and fishing along the Colorado River and its tributary streams, and boating and fishing in the reservoirs of the major multiple-purpose projects. A Survey of the Recreational Resources of the Colorado River Basin, which the National Park Service compiled in 1946 and published in 1950, notes that "in the arid portions of the basin the creation of large artificial lakes or reservoirs is of great recreational importance." The survey, cov- ering about 135 potential reservoir sites, stated that "the recreational potentialities of these sites will be considerably increased in a number of cases- particularly the smaller reservoirs-if a dead stor- age or conservation pool can be assured. High evaporation losses, however, will need to be bal- anced against these recreational advantages. A number of reservoirs are proposed in locations where the existing natural features are of greater recreational value than can be expected of the proposed reservoirs. A majority of the proposed reservoirs, however, will create new recreational resources benefiting the basin." Program for Development Provision for recreation facilities at the various major reservoirs is planned. Fish are to be prop- agated, and opportunities for boating, bathing, picnicking, and camping are to be provided where they do not interfere with other important reservoir uses. Fish and Wildlife The Present Situation The Colorado River Basin constitutes one of the great primitive wildlife and stream fishery areas in the United States. Stream conditions vary from clear, cold, high, mountain streams to warm and often silt-laden waters of lower elevations. That part of the western slope of the Continen- tal Divide falling within the upper basin consti- tutes one of the greatest hunting areas in conti- nental United States. Deer are abundant in most of the basin and elk are numerous at the higher elevations. Antelope are found on the high, tree- less plateaus, moose in the wilderness areas of the upper reaches of the Green River, and several large |