Page 2

LIMITED OFFICIAL USE -2- The Wellton-Mohawk irrigation district in Arizona is the source of the difficulty. In total tonnage of salts, its pumps are discharging four times more salt than is received in irrigation waters. Scientific investigations conducted in March 1962 showed that the root zone (the top six feet) of the acreage being cultivated was relatively free of salt and that, except for small areas, it was no longer essential for purposes of reclaiming the land or carrying on agriculture to discharge more salt from the district than it has been receiving in its irrigation water. Our study of the case has led us to conclude that it would be extremely difficult to sustain a contention that the terms of the Water Treaty allow the United States to carry on irrigation practices which have such adverse effects on the irrigation activities of downstream users in Mexico. I believe we still have an opportunity to adopt measures which will avoid a crisis in our relations with Mexico and protect the interest of the Colorado Basin States. I doubt that we will have comparable freedom of action a month or two from now when we are in the midst of a crisis. We can get the salinity of the water down to a reasonable level: a) this winter by requiring the Wellton-Mohawk to reduce its pumping. This can be done with almost no injury to the district by coordinating its pumping schedule with Mexico's diversion schedule so that the district pumps at one-third capacity while Mexico is diverting, and at 100 percent capacity when Mexico is not diverting. (The same objective could be achieved by releasing about 300,000 acre feet of stored water from Lake Mead to dilute the saline water, but this does not appear to be politically feasible.) :hw: 1500 ppm 200 or so f/p/s. w-m 200 to 800 released :/hw: b) in the long run, by constructing a by-pass channel so that the Wellton-Mohawk drainage in excess of "salt balance" enters the Colorado below Mexico's main diversion point. (Use of tile drains is understood to be technically feasible, but expensive and strongly opposed by the district.) LIMITED OFFICIAL USEEpson Perfection 4870 Photo, 400 dpi, 8 bit, 10,408,960 byte