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-- -- - 0 ""?-.;-r.r.- U 1., '" :1 t Salinity of the. Lower Colorado River/37 hawk District drainage waters. The remainder was from drainage waters from other United States projeets below Impe- rial Dam. There was general accord that the salinity differential ad- versely affected production in the MexicaH Valley, but the ex- tent of the effect was debated by technical experts in the two countrtes. United States experts estimated the effect to be rela- tively small at contemporary salinity levels. 2. Cooperation for Development. Authorities from both countries recognized other factors affecting Mexico's long- range agrtcultural production. Mexico was then making major improvements in their irrtgation and drainage system and management practices, at a cost of about $150 million (U.S.). These programs were partially supported by loans from the In- ternational Bank for Reconstruction and Development and the Inter-American Bank. Mr. Brownell recognized that salinity above Imperial Dam would increase slgnlflcantly as water uses expanded. Un- less measures were taken to stem the increase, they would ad- versely affect downstream users, both in the United States and Mexico. The Department of the Interior was then studying a program of remedial measures to maintain Impertal Dam wa- ter at or below its level of 850 ppm, which was the forerunner of a program adopted later. 3. Groundwater Pumping. As discussed above, Mexico de- cided in 1971 to reduce the salinity of the waters it received by requesting that the U.S. bypass additional Wellton.Mohawk drainage waters, with the quantity bypassed counted as a de- livery under the treaty. To replace the unused ."treaty deliver- ies," the Mexican government began extensive groundwater pumping on the San Luis Mesa just south of the international boundary between Arizona and Sonora. Since the pumping would draw groundwater from the United States side, deprtving United States users of the same resource, the United States proposed installation and operation of wells on its side of the boundary to offset Mexico's pumping of groundwaters by inter- cepting most of the flows before they could reach Mexico. 4. Mr. Brownell's Recommendations. Mr. Brownell rec- ommended that a negotiated. rather than adjudicated, solution be sought to the salinity problem because the differences among legal and technical experts were so deep that adjudica- tion could delay a solution for many years. Moreover, an adju- dicated decision would probably not be as satisfactory to either side as would a solution worked Q!lt between the two eountIies. Mexican officials with whom the'Salinity issue was discussed in November, 1972, agreed that a frtendly, negotiated solution