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~~ ',-' t~ ':SJ to reaching an agreement,s but in early 1972 the Mexican government rejected U.S. proposals. Q In June 1972 Ptjesident Echeverria arrived in Washington with a stronger demand: parity. 'El ~ Mexicali Valley ifarmers should receive water of the same quality as American water users f,):l ~~served by ImpedaI Dam, then about 870 ppm. ~\~1 .t:3 r<"1 ~d j~;;~ f:~l ~;:] m -~~ .;0;-;" :f}] f$-:'~ ~t'?-~ i~~ .~] ~~i~ ~,~, ~ ~:.:.,;' f~ ,'~<I' ~;;:~ i'-:.J. t1:J ."; ~ >. ';.:.~~: ';"-~ President Nixon ~sponded in a joint communique issued June 17, in which he promised to: 1) take action imm~ately to improve the quality of water going to Mexico; 2) appoint. a special representative to lfind a "permanent, definitive and just" solution to the salinity problem and report to him bY: the end of the year; and 3) submit a U.S.-approved proposal to Presidept Echeverria for Cl!lnsideration and approval. The mwc was directed to draw up and sign a Minute containin$ this program.9 In preparation for the Mexican President's visit, the Office of Management and Budget (OMS) and the Departmdnts of State and the Interior, briefed President Nixon on possible diplomatic courses of action ~d short- and long-term measures to reduce salinity levels of water delivered to Mexico. In th~ short run, bypassing some portion of retumflows and rc!placirtg it with better quality water fro,* another source seemed the only practical means. Long-term solutions f~U into four categori~: 1) continuing to bypass Wellton-Mohawk return flows and substituting less saline water from! other sources (including "new water" from weather modification and other augmentation techpologies then under study); 2) eliminating salt loading by totally or partially. shutting down theiproject; 3) desalting all or part of the return flows; and 4) regulating salinity according to state-by-state water quality standards, restricting irrigation or requiring more efficient on-farm ",ater management practices where necessary. Before the Echevetria visit, the simplest and least expensive course of action appeared to be to continue to bypass:-and substitute better quality water for-some portion of the return flows, while the issue qf an acceptable salinity level was resolved diplomatically. After the Wellton-Mohawk project reached salt balance, the U.S could undertake more costly or controversial measures to permanently maintain the negotiated salinity level. This approach had several advantages: it would have given Mexico an immediate reduction in salinity; preserved the legal positions of both parties during negotiations over ultimate salinity levels, and deferred capital expenditur~ or politically unpopular decisions. The Colorado Basin states had been willing to support tfIe equivalent salt balance concept; presumably they would have agreed to the use of substitution water from a source within the Basin for a limited period. 10 , ;; '< '! Minute No. 241, th~ interim Minute required by the joint communique, was signed on July 14. It reflected the approach described above: the U.S agreed to bypass 118,000 acre-feet of Wellton-Mohawk dJ:ainage per year, replacing it with additional water released from Imperial Dam. This action ~ould have reduced the salinity level at Morelos Dam from 1,240 ppm (under Minute No. 218, th~ interim 1965 agreement) to 1,140 ppm-the salt balance level, though the term was not mentij:>ned. Mexico, however, asked the U.S. to bypass the remaining 100,000. acre-feet of drainag~ without substitution, which resulted in a salinity level of about 950 to 1000 ppm. Here the diplomatic situation became murky. Why did Mexico agree to let the U.S. limit its efforts, even in the :interim, to guaranteeing a level of salinity corresponding to that resulting 4 " ,4)-]- ~,i1~