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<br />. <br /> <br />. <br /> <br />. <br /> <br />o <br /><.0 <br />W <br /> <br />SPECIAL STUDIES (Continued) <br /> <br />CD <br /> <br />F. Lower Colorado River Salinity Investigations <br /> <br />In February of 1970, the Bureau of Reclamation began a trial pro- <br />gram to analyze the source and makeup of the salt load arriving at <br />Imperial Dam on a daily basis. Conductivity measurements were made each <br />day at 10 stations between Parker Dam and Imperial Dam. The network <br />included essentially all significant diversions, surface return flows, <br />and major river stations. <br /> <br />An intensive program was carried on for one year. After one year <br />of operation, the frequency of sampling was reduced. During the fall of <br />1971, an experimental program of automatic salinity monitoring was <br />started. Conductivity probes were installed at nine stations on the <br />lower river and the data transmitted by telemetry to the Boulder City <br />and Imperial Dam offices. The nine stations are as follows: <br /> <br />l. <br />2. <br />3. <br />4. <br />5. <br />6. <br />7. <br />8. <br />9. <br />Morelos <br /> <br />Colorado River below Hoover Dam. <br />CRIR Main Canal near Parker. <br />Poston Wasteway near Poston. <br />Palo Verde Canal near Blythe. <br />Colorado River at Taylor Ferry near Cibola. <br />Colorado River below Cibola Valley. <br />Yuma Mesa Drain near Yuma. <br />Main Outlet Drain Extension Bifurcation for MODES 2 and 3. <br />Colorado River at the Northerly International Boundary <br />Dam. <br /> <br />above <br /> <br />Recently the Intensive Salinity Surveillance Program was changed. <br />The water quality telemetering program was discontinued but weekly <br />samples are taken at the nine previously mentioned stations. Daily <br />conductivity measurements are taken at Imperial Dam in conjunction with <br />the requirements of meeting Minute 242. The USGS is now responsible for <br />the continuous water quality monitoring probes at Imperial Dam and on <br />the Main Outlet Drain Extension for both continued research and data <br />gathering. There are plans to install continuous monitoring probes at <br />Hoover and Parker Dams and at Needles. The installation at Needles will <br />test three different probe systems to determine which best suits the <br />needs of that and future sites. <br /> <br />In addition to the nine formerly telemetered stations, water <br />quality samples are collected from five other stations. Individual <br />samples are analyzed for conductivity. The U.S. Geological Survey <br />Laboratory makes weekly analyses for total dissolved solids (residue at <br />1800 C) and monthly analyses of the chemical constituents. <br /> <br />Sampling frequencies for all stations were selected from an anal- <br />ysis of past records so that samples would represent the actual salt <br />load with an error of less than 5 percent, 95 percent of the time. The <br /> <br />120 <br />