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<br /> <br />OPERATING, MANAGEMENT AND FINANCIAL PROBLEM.8 <br />OF LOCALLY OPERATED AND CONTROLLED PROJECTS <br /> <br />(Group discussion of' the subject was led by Evan T. Hewes and <br />R. J. McMullin, with Hampton C. Godbe. as moderator.) <br /> <br />*********** <br /> <br />PROBLEMS OF IMPERIAL IRRIGATION DISTRICT <br />:RELATING TO SALTON SEA, DRAINAGE, AND QUALITY OF WATER <br /> <br />M. J. Dowd, consulting Engineer <br /> <br />I - ;SALTON SEA <br /> <br />Descl'iption of' Basin <br /> <br />Salton Sea, :l.n northern IIn;perial County and southern Riverside <br />County, CElli1'ornia, is the "sump hole" of an enclosed basin comprising <br />7,500 square miles, of' which about 1,000 squal'e miles is in Mexico. The <br />basin extends from San Gorgonio Paps some 200 miles southeasterly to the <br />ridge that divides the Colol'ado River delta between that part which dl'ains <br />southerly into the Gulf of' Calif'oI'Ilia and that part which dl'a:l.ns northerly <br />into Salton Sea. At its lowest point, the ridge is 47 feet above sea level. <br />A large part of' this basin is below sea level, the lowest point 273.5 feet <br />below. Salton ~ea l'eceives not only the storm. runoff f'rom this basin, but <br />also the dl'ainage from 550,000 acres 01' presently iTl'igated land in Impel'ial <br />and Coachella Valleys, California} and 150,000 acres in the MexicaU Valley <br />of' Mexico. <br /> <br />Past Overf'lows into Basin <br /> <br />In past ages the bas:l.n. has been f'illed to various depths over <br />long periods by overflow from Colorad.o River, during which. silt was <br />deposited to depths of'mol'e than l,OOO feet. Overflow created a large <br />lake in the 80fs, and again in 1891 when it covered 100,000 acres. How- <br />ever, dry years f'ollowed and the basin was dry when man commenced development <br />of' Imperial Valley in 1900. <br /> <br />River Break of' 1905-07 <br /> <br />As a result of' a break in 1905, the entire Rive.l' discharged into <br />the Valley for nearly two years, and created the present Balton Sea. At <br />closure 01' the break in February 1907, the Sea covered 350,000 aCl'es and <br />had an elevation 195 feet below sea level. For the next 13 years exc.ess <br />of' evaporation over inflow caused the Sea to dl'op rapidly. However, by <br />1920 return flow from irl'igation in Imperial and Mexicali Valleys caught <br />up with evapol'ation, and the rate of lowering slowed down. From a low 01' <br />250 feet below sea level in 1925 the Sea rose 7 feet by 1931, due to a <br />plentiful water supply for irrigation and severe local storms. Thereafter <br /> <br />-25- <br />