Memorandum of Conversation on Colorado River Salinity

Memorandum of Conversation: From J.F. Friedkin, to the two Commissioners and the two Secretaries, "Colorado River Salinity," July 3, 1964, page 4CONFIDENTIAL -4- waters from greater depth and of higher salinity, and that samples from the root zone, even if representative and this is near impossible, would not reflect the probable flows from gravity drains. The results may be better and may be worse than the index of 1.5:1. I pointed out that the results of gravity drains could be ascertained only by experience with the installed drains which may take two years or more. While conceding this, the Mexican Commissioner still expressed important need for supporting data in some form for the index of 1.5:1, in order for Mexico to consider its justification. On this point he further noted that with time the salt balance ratio should materially reduce because of 1) increased diversions, and 2) reduction in soluble salts in the soils. He noted that records of the Yuma Valley Irrigation District indicate an index of practically 1:1. While noting that the United States anticipated an improvement to less than 1.5:1, he also noted that there was no promise of a reduction with time. He referred to substitution of well waters for normal returns and emphasized that this should not increase the salinity to Mexico. There was an implied concern that if adopted, the United States may use the 1.5:1 index as a basis for substituting well waters of poorer quality for normal returns. The Mexican Commissioner expressed a further view as regards the salt balance index of 1.5:1. He noted that on the basis of Mexico's treaty allotment of 1.5 million acre-feet, if the total normal return flow from the District amounted to 220,000 acre-feet, and if the amount to Mexico were reduced by means of a bypass channel to say, 150,000 acrefeet, and if it carried the full salt tonnage of 220,000 acre-feet of normal returns as contemplated: Mexico would have to receive more salts than if there were normal returns from the District and more than the quantity corresponding to the 1.5:1 index. The increase would be the tonnage of salts carried by the additional 70,000 acre-feet of water to make up for the reduction in returns incident to the bypass operation. He expressed the view that there should be an adjustment for this in determining the salt balance. [70,000 tons would be about 10% of the Wellton-Mohawk return; adjustment, if allowed, would reduce the salt balance from 1.5 to 1.4:1] I advised the Commissioner that if deliveries to Mexico could be rigidly limited to 1.5 million acre-feet he would be correct, but actually there will most likely be some excess waters such that the 70,000 acre-foot reduction in returns would not result in increased releases and hence no increase in salt quantity over that which Mexico would otherwise receive. [The net effect would be no increase in tons of salts to Mexico but a decrease in water to Mexico by about 70,000 acre-feet]. Steps to Put Agreement into Effect Our discussion developed complete understanding that the first and urgent requirement of the negotiations is to reach an agreement upon the CONFIDENTIALEpson Perfection 4870 Photo, 400 dpi, 8 bit, 2,375,043 byte