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<br />2357 <br /> <br />THE SALT PROBLEM <br /> <br />Salt Discharge to River <br />The Colorado River Indian Reservation is intimately connected to <br />the river system because virtually all inflow comes directly from the <br />Colorado River (an exceptions is minor overland runoff caused by <br />rain), and all outflow enters the river. Agricultural drainage from <br />the Reservation contains salt that was present in the diverted water <br />and salts that are picked up beneath the surface of the flood plain. <br />Since 1970, the Bureau of Reclamation has conducted an <br />Intensive Salinity Surveillance Program (ISSP) on the Colorado River <br />between Parker Dam and Imperial Dam. The program involves regular <br />sampling of water quality in major diversions, agricultural drains, and <br />the river itself between Parker Dam and Imperial Dam. The data are <br />combined with provisional Geological Survey data on the quantities of <br />diversions from the river and drainage to the river, and estimates are <br />made of the annual tonnages of salt passing various points in the <br />system. <br />The ISSP data from within the Reservation indicate that the <br />Reservation drains generally discharge less salt to the river than is <br />contained in the water diverted from the river. Thus the Reservation <br />tends to remove salt from the river system. The measured annual <br />salt discharges are as follows (negative values signify salt retention): <br />Measured <br />Salt Oi scharge <br />Year in Tons <br /> <br />1968 -37,736 <br />1969 -19,646 <br />1970 22,240 <br />1971 -36,940 <br />1972 6,213 <br />1973 -62,374 <br />1974 -45,273 <br />1975 -68,108 <br />1976 -9,348 <br />1977 -51,019 <br />Average -30,200 <br /> <br />11 <br />