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002582. On main river channels, uncontrolled water spreading into adjacent alluvial deposits greatly increases the loss of water to evaporation and to nonbeneficial vegetative growth. This condition exists on the main stream of the Colorado River, in many areas on the Gila River, and also along many other streams of the Pacific Southwest. By channelization and phreatophyte eradication, signi- ficant quantities of these nonbeneficial losses could be salvaged. Selected vegetative areas should be maintained for wildlife pur- poses; however, this factor should not be allowed to overshadow the urgent need for conserving the water supplies of an arid land for the benefit of all its inhabitants. Channelization of streams could permit passing higher floodflow discharges without the erosion of developed flood-plain areas, and could ease present sedimentation problems. Many irrigation ditches and practices, born during the early history of western irrigation, still continue to exist. Wherever highly erratic ~ater supplies made canal washouts an ever-reoccurring loss, these primitive canal systems and irrigation practices were an economic necessity. Due to almost full regulatory control of the Colorado River and full or partial regulation of tributaries, these conveyance and distribution systems should be lined. Unlined, they 1058 precious developed water and for many smaller irrigated areas, especially with uncertain surface-water supplies, these losses further suppress an uncertain production. This condition is not confined to small and remote ditches but applies to major canal systems throughout the Pacific Southwest. Progress has and is being made toward lining these canals or install- ing closed-pipe systems; however, many miles of canals remain to be improved. In the Pacific Southwest, where some areas perennially suffer water shortages and economic losses, salvage of waters lost by irri- gation inefficiencies and historic overdiversions could do much to bolster the water economy of the area. In addition, trespassers along the Colorado River between Davis Darn and the International Boundary, with major water users not yet under permit by the Department of the Interior, are diverting an estimated 200,000 acre-feet annually from the river. No one should be allowed to indiscriminately use water, for whatever reason, to the detriment of others. Steps should be taken immediately to conserve these waters. Evaporation reduction on all Pacific Southwest reservoirs could do much to improve the stability of water reserves, as many hundreds of thousands of acre-feet of water are annually lost. It is abundantly clear that because of the complexity of the problems involved in developing new sources of water for the Pacific lV-3