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<br />. I <br /> <br />A. Authority for the Status Report <br />The preparation of this report is authorized by the Federal Reclamation Laws (Act <br />of June 17. 1902, 32 Stat. 388 and Acts amendatory thereof and supplementary thereto). <br />B. Scope of Investigation <br />The scope of this investigation is to develop detailed locations. sizes. and operating <br />criteria for the features to be constructed, and objectives and details of the implementation <br />of nonstructural measures of the Desalting Complex Unit of Title I Division of the Colorado <br />River Basin Salinity Control Project. Separate investigations are being conducted to develop <br />final plans for the Coachella Canal Unit, the Protective and Regulatory Pumping Unit. <br />and replacement sources for the desalting plant reject stream. <br />e. History <br />The initial factor which led to the eventual inception of the Desalting Complex Unit <br />was the increase, in 1961. of total dissolved solids (TDS) in the Colorado River water <br />delivered to Mexico at the Northerly International Boundary. The average annual salinity <br />of the water increased that year fron; about 800 parts per million (p/m) TDS to nearly <br />1.400 plm TDS. then to nearly 1,500 plm TDS in 1962 (all salinity measurements cited <br />herafter are considered to be TDS). Two concurrent and principal factors led to this <br />increase in salinity. In 1961, the pumping of saline waters (initially averaging 6,000 p/m) <br />was begun by the WMIDD to lower ground-water levels below the crop root zone in the <br />aquifer that underlies the Division. This drainage was discharged to the Gila River, a <br />tributary of the Colorado River. and consequently delivered to Mexico at the Northerly <br />International Boundary. Also, excess Colorado River flows. which Mexico had received <br />prior to 1961, significantly decreased due to low runoff in the upoer basin. This latter <br />situation has continued with the filling of Lake Powell since 1963. <br />Prior to this time there had never been any definite stipulations concerning the quality <br />of water to be delivered to Mexico. The Colorado River Compact of 1922 [I] only <br />contemplated. under Article llI(c). that the United States might, as a matter of international <br />comity, thereafter recognize in Mexico a right to use of waters of the Colorado River <br />system. The Treaty of 1944, between the United States and Mexico, entitled Utilization <br />of Warers of the Colorado and Tljuana Rivers and of the Rio Grande [3], provided for <br /> <br />. <br /> <br />. <br /> <br />2 <br />