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R. '~i . ,f:: ,~ 'kJ !i; , " ? "..~. " ',i-,' [1 ,,:;J 'a:' .. *::. ~>~. ~:. '>,:' ~.' .~! ..3> ;'~~ ~i ....1 J;'j t~~ ~~ ,~:: ~;;.. ~~~ 'f$;~ ~J ~i1 fJ~t [fJ .~'~,~ "2 b ~] ~;~,} ~:~~j ;::;; '. ~'~ ~s: .:~q i~~~ used-and stilll\ses-most of its Colorado River water to support irrigated agriculture in the Mexicali Valley" this silence seems odd. The history of the treaty suggests that the U.S. and Q Mexico drew different inferences about quality from the phrase "any and all sources." ~ = Before the comPletion of Hoover Dam in 1935, destructive spring floods swept through the Colorado Basin almost every year, followed by dangerously low flows in the summer. When the river was in its natural state, Mexico could capture and use only about 750,000 acre-feet of water per year. iHoover Dam made possible the storage of floodwaters and year-round flow regulation, and Mexico stood to receive much more usable water-but the legislation authorizij)g the dam's constn!iction barred foreign governments from receiving any benefit from it! The 1944 treaty contained an apparent compromise: the U.S. would deliver approximately twice as much water to Mexico as it would have been able to use had the Colorado River not been regulated (1.5 milllon acre-feet) but Mexico would have no say in the source of that water within the Basin, nor in its quality.2 Until 1961, no problems arose from the salinity of water deliveries. In that year, the Wellton-Mohawk:Irrlgation and Drainage District in Arizona, near the Mexican border, began to operate a pumPed drainage system. To lower the high water table beneath the project, it began to pump highly saline water into its. drains-water that was laden with salts that had accumulated in th~ soils beneath the project from decades of irrigation without drainage. These drainage waters, or "return flows" carried about 6,000 parts per million (ppm) of dissolved saltS, and entered the river just above Morelos Dam, the main Mexican diversion point. In the same year, :the U.S. sharply reduced upstream releases-which would have diluted the brackish drainage waters from Wellton-Mohawk-in order to begin filling Lake Powell behind the newly completed Glen Canyon Dam. These two events caused the average annual salinity of water delivered: to Mexico at Morelos Dam to jump dramatically, from about 800 ppm in 1960 to 1,340 ppni in 1961, to more than 1,500 ppm in 1962. Salinity levels in some months exceeded 2,500 PPln. In November 1961, the government of Mexico filed a formal diplomatic protest, Charging d1e U.S. with violating international law. The International Boundary and Water Commissioni(IBWC), the joint U. S, -Mexican agency charged with administering the 1944 . treaty, began negotiations on a practical solution. For the next ten years, Mexican and U.S, scientists, diplomats, and Federal and state officials debated the intent ;of the 1944 treaty, technical issues, and equities under international law without reaching a permanent solution.3 The Committee of Fourteen-composed of two representatives from each of the seven Basin states- had been created in 1938 to consider basin- wide problems, in~luding the prospective treaty. At the State Department's request; the Committee was revived in the early 1960s to advise the U.S, Section of the mwc on the salinity issue. In 1965, the U.S., under Minute No. 218 of the IBWC, agreed to several temporary measures to reduce salinity: extending the Well ton-Mohawk Drain to permit drainage to be bypassed around Morelos DaJj:! (where it would flow to the Pacific Ocean without being diverted for use) during periods of unusually high salinity; replacing about 40,000 acre-feet per year of bypassed , I . . . '1 2 '; ~, ~\" t: .,~~:a