Page 6

With the present cropping pattern of 75% cotton and 25% winter wheat, applied to the reduced cultivated area of 407,000 acres, consumptive use of irrigation water should not be more than 1,500,000 acre feet (175,000 acre feet for 102,000 acres of winter wheat, and 1,325,000 acre feet for 305,000 acres of cotton). Additional water is required for leaching and to make up for canal leakage, etc. Ultimately, the annual amount of water available will be 1,500,000 acre feet from deliveries under the Treaty, plus at least 780,000 acre feet from wells in the Mexicali Valley. This total of at least 2.28 million acre feet corresponds to an annual allotment of 5.6 feet of water over the 407,000 acres to be irrigated. According to Director Bower of the United States Salinity Laboratory, this allotment "seems reasonable for water of salinity not exceeding 1,500 to 1,800 parts per million." A pumping rate of 780,000 acre feet per year would require about half the pumping capacity of the present wells in the Mexicali Valley. It is about 7% greater than the amount of water actually pumped during 1961. but is considerably less than the present ground water recharge. The American members of the Joint Panel have urged an acceleration of the remedial works in the Mexicali Valley, and of the planned reduction in acreage. This recommendation has been concurred in by the Mexican members of the Panel. Until the recommended construction program for the Wellton-Mohawk project can be completed, short term measures must be taken. Mr. Dominy. Commissioner of the United States Bureau of Reclamation, informed the American members of the Panel and other interested parties at a meeting on April 26, 1962, that during the winter of 1962-63 he planned to use for river regulation some 280,000 acre feet of water accumulated in storage reservoirs. These additional releases for channel control would have the incidental benefit of reducing the sait content of waters delivered to Mexico during this period. During the following winter, it is possible that the pumping of wells on the Wellton-Mohawk project could be reduced and be made sufficiently selective in terms of quality of water, so that the salinity of the effluent would not be too seriously high. However, the Mexican members of the Panel believe it is essential that the by-pass channel should be constructed and placed in operation by October 1, 1963. so that, if necessary, some or all of the drainage water from the Wellton-Mohawk project could be wasted. 6Epson Perfection 4870 Photo, 400 dpi, 24 bit, 2,980,352 byte