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<br />IV. PROBLEMS AND NEEDS <br /> <br />Historical <br /> <br />Salinity ultimately becomes a major problem in many irrigated areas. <br /> <br />In areas with high saline soils, such as west central Colorado, salinity has <br /> <br />affected water quality since irrigation was first attempted because the <br /> <br />irrigated land and diffused source areas contain large deposits of salts. <br /> <br />In recent years salinity concentrations in the Colorado River have adversely <br /> <br />affected downstream irrigated crop production and other water uses. The <br /> <br />problem is especially severe for water delivered to California, Arizona and <br /> <br />Mexico. <br /> <br />The Colorado River system naturally carries a large load of salts <br /> <br />(dissolved solids) and suspended sediment. Streamflow depletions resulting <br /> <br />from transbasin diversions, and for irrigation, municipal and industrial <br /> <br />uses significantly reduces the supply of water available for dilution of <br /> <br />salt loads in the lower river system. Future development of compact appor- <br /> <br />tioned water by the Basin states will further reduce the water available for <br /> <br />dilution, and in some cases the development projects themselves may increase <br /> <br />salt loadings in the river system. <br /> <br />Recognition of the water quality problem in the region has caused a <br /> <br />number of studies to be made since about 1960. The Colorado River Basin <br /> <br />Water Quality Control Project was established in 1960 by the Division of <br /> <br />Water Supply and Pollution Control, U.S. Public Health Service. Studies by <br /> <br />the Environmental Protection ~gency (1971) produced a series of reports on <br /> <br />"The Mineral Quality Problem in the Colorado River Basin". Salinity in the <br /> <br />river also is documented by the Water and Power Resources Service (1972 and <br /> <br />1974) Status Reports - Colorado River Water Quality Improvement Program, and <br /> <br />U.S. Geological Survey Professional Paper 441, "Water Resources of the Upper <br /> <br />Colorado River Basin - Technical Report" by Iorns and others (1965). <br /> <br />001232 <br /> <br />IV-1 <br />