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<br />PROBLEMS <br /> <br />Historical - Salinity ultimately becomes a major problem in many irri- <br />gated areas. In irrigated areas with high saline soils, such as the <br />Grand Valley in west central Colorado, sal inity has been a problem since <br />irrigation water was first de; ivered. Irrigated land in the valley and <br />the diffused source areas with highly saline soils and subsoils are <br />large contributors of saline return flows. In recent years salinity <br />concentrations in the Lower Colorado River have adversely affected <br />irrigated crop production and other uses. This problem is especially <br />severe for water del ivered to Cal ifornia, Arizona, and Mexico. <br /> <br />, <br />\ <br />. . <br /> <br />The Colorado River system naturally carries a large load of salts <br />(dissolved solids) and suspended sediment. Depletions in streamflow <br />resulting from transbasin diversions, and for irrigation, municipal and <br />industrial uses has significantly reduced the supply of water available <br />for dilution of salt loads in the lower river system. Future develop- <br />ment of water by Upper Basin states will further reduce the water avail- <br />able for dilution, and in some cases the development projects will <br />themselves increase salt loadings in the river system. <br /> <br />Recognition of the water quality problem in the region has caused a <br />number of studies to be made since about 1960. The Colorado River Basin <br />Water Quality Control Project was establ ished in 1960 by the Division of <br />Water Supply and Pollution Control, U. S. Public Health Service (pre- <br />decessor to the Federal Water Quality Administr2tion). Their studies <br />produced a series of reports on "The Mineral Qual ity Problem in the <br />Colorado River Basin" by the Environmental Protection Agency (1971). <br />Sal inity in the Colorado River is also documented by the U. S. Bureau of <br />Reclamation (1972 and 1974) Status Reports - Colorado River Water Quality <br />Improvement Program, and U. S. Geological Survey Professional Paper 441, <br />"Water Resources of the Upper Colorado River Basin - Technical Report," <br />by lorns and others (1965). <br /> <br />The Federal Water Pollution Control Act Amendments of 1972, PL 92-500, <br />in Section 303 require adoption of water quality standards applicable to <br />interstate waters. The Act's objective is "to restore and maintain the <br />chemical, physical, and biological integrity of the Nation's waters" <br />(Section 101), and the administrator is required, io cooperation with <br />other Federal, State, and local agencies, "to develop comprehensive <br />programs for preventing, reducing, or eliminating the pollution of <br />navigable waters and ground waters" (Section 102 [a]) . Pursuant to that <br />requirement, the Environmental Protection Agency on December 18, 1974, <br />issued a regulation requiring states of the Colorado River Basin to <br />adopt water quality standards for salinity, consisting of numeric <br />criteria and a plan of implementation for salinity control. The stan- <br />dards, submitted for apprOVal to the Environmental Protection Agency <br />before October 18, 1975, are to be reviewed at 3-year intervals and <br />modified, if appropriate. <br /> <br />5 <br /> <br />16'78 <br />