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<br /> <br /> <br />~ <br />~ <br />o <br />:.." <br /> <br />small increases in average mineral concentrations, particularly <br /> <br /> <br /> <br />toward the end of the period, caused by construction of reservoirs, <br /> <br />increased irrigation, and out-of-basin diversions. The research <br /> <br />also found that most of the mineral burden of the Colorado River, <br /> <br />like most of its flow, originates in the Upper Basin. The largest <br /> <br />individual incremcnt to the mineral hurden of the Colorado River <br /> <br />below the Compact point and above Imperial Pam was found to be the <br /> <br />Blue Springs located near the mouth of the Little Colorado River. <br /> <br />The report further shows that a principal increase in salinity in <br /> <br />the lOwer reach is derived from irrigated land in the Parker and <br /> <br />Palo Verde valleys. The increaSing out-of-basin diversions are <br /> <br />also reported as Contributing to the rising salinity concentration <br /> <br />levels. <br /> <br />The ~lineral Qua Ii t Problem in the Colorado River Basin (EPA) <br /> <br />In 1971, the EPA releasea its report entitled "The /lineral Quality <br /> <br />Problem in the Colorado River Basin." In this report, salinity and <br /> <br />streamflow data for the 1942-1961 period of reCord were used as a <br /> <br />baSis for estimating averagc salinity concentrations under various <br /> <br />conditions of water development and use. IInder these conditions, <br /> <br />concentrations at HOover Dam wcre estioated to average about 70D and <br /> <br />760 mg/I in I96D and 1970, and 880 and 990 mg/I in 1980 and 2DID, <br /> <br />respectively. At Imperial Pam, the report estinates 76D and 870 mg/I <br /> <br />18 <br />