Page 2

CONFIDENTIAL -2- Reclamation review the practicability of the reduction of pumping in the District, supplemented by tile drainage works. A reduction in pumping is suggested in light of the lowering effected in the ground water table during the past eighteen months and the Department's understanding that the current rate of drainage pumping (210,000 acre feet per year) is that required for full project development of 75,000 acres, whereas for the some 60,000 acres now under irrigation, pumping of only about 170,000 acre feet annually is required. The Department believes that a reduction of 40,000 acre feet can be achieved by a 45% decrease in the rate of pumping during the winter months without a material rise in the water table that will result in water logging of any of the cultivated acreage. The District wells were completely shut down what ??? for about 10 days in November-December 1961 when ground water levels were considerably higher, with no serious adverse effects. see table 8 p. 49 what hearing? A reduction in pumping will probably be required in the equivalent of only four of the five winter months because Mexico may not need to irrigate during the other month. Resulting salinity to Mexico would be in the rang of 1600 ppm to 1900 ppm depending upon the quantity of river flows. Tile drains should be installed in the possible danger spots in the District lands as suggested in the Bureau Report. Such supplemental drainage works would also enable some further reduction in salinity of waters to Mexico during the coming winter. A combination of reduction in pumping supplemented by tile drains would result in mean salinity water to Mexico at the northerly boundary in the range of 1400 to 1700 ppm depending upon the quantity of flows in the river. This would afford material interim relief to the problem. not 1963-64 The Bureau of Reclamation proposed the installation of additional pumps in Phase 1 of its program. The Department of State agrees that additional pumps are required as an essential part of the long term solution, but does not concur in the proposed method of operation suggested by the Bureau for either interim or permanent relief. The Bureau proposed that the highest salinity wells be pumped in summer, and the lowest in winter. Our analysis of this method of operation has convinced us that this would aggravate the problem because it would result in further serious deterioration in the quality of the water for Mexico's principal summer crop. The Department believes that the lowest salinity wells should be pumped in the summer to achieve an improvement in the quality of summer waters and that the highly saline wells should be pumped in the winter with the drainage to be diverted below Morelos Dam. B. A long term CONFIDENTIALEpson Perfection 4870 Photo, 400 dpi, 8 bit, 3,921,920 byte