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o )~ , ..... CQ ! ! i I I i I I ! I I I , I I 1 , , , ! . . I I I I I 1 i I I ~ I r ! A.M.D.G. INTRODUCTION A. The Salinity Problem and Subsequenl Recommendalions The Colorado River rises in the Rocky Mountains and flows southward for 1,400 miles before emptying into the Gulf of California. As the river proceeds from its head- waters to the gulf, numerous diversions are made from the' stream for purposes of irrigation and excess diversions are returned to the river causing the water to become progressively more saline. In a recent study the average mineral salt content for the five-year period 1953-57 was shown to be about 90 parts pel' million near the headwaters of the Colorado River as compared with a salinity level of more than 800 parts pel' million below Morelos Dam at the international boundary.' Waters of the Colorado River are used in Mexico for the irrigation of lands in the Mexicali Valley, delivery of such waters being the subject of a treaty entered into between Mexico and the United States in 1944. Water is diverted at the Morelos Dam located about a mile below the California-Mexican boundary and is conveyed via the Alamo Canal to irrigate lands west of the Colorado River. During the last months of 1961 a substantial incrcase occurred in the salinity of waters delivercd to Mexico at the Morelos Dam. In the winter of 1961-62 salinity in- creased to about 2,600 ppm( the increase coinciding with the opening of a large drainage program in the IVellton- Mohawk division of the Gila Project near Yuma, Arizona. The drainage program consisted in the drilling of a large number of drainage wells in an attempt to lower a rising groundwater table which was threatenb:;g much of the 1 Salinity Problems in the Lower Colorado River Area, Colorado River Board of California, Plate 1, Sopt. 1962. 2 Joint Report of United States and Mexican Expert Panels on Colorado River Salinity Problem, El Paso Draft 7, May 5, 1962. 1