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<br />,) <br /> <br />2. Future Quality of Water Delivered to Hexico. The water <br /> <br /> <br />to be delivered to Mexico under Phases 1 and 2 of the proposed <br /> <br /> <br />program will not have any deleterious effect on soil productivity <br /> <br /> <br />insofar as exchangeable sodium levels are concerned. The sodium <br /> <br /> <br />adsorption ratio under Phase 1 will range from 4.7 to 6.5 and from <br /> <br /> <br />5.3 to 5.9 under Phase 2. The dissolved mineral content of water <br /> <br /> <br />delivered to Mexico will be approximately 2,000 ppm and 1,800 ppm <br /> <br /> <br />after construction under Phases 1 and 2, respectively, is completed. <br /> <br /> <br />At the present time, the unfavorable salt balance in the Mexicali <br /> <br /> <br />Valley is primarily due to the lack of adequate leaching of excess <br /> <br /> <br />soluble salts from overextension of the cropped area. The situation <br /> <br /> <br />in the Mexicali Valley today was not brought about by a year of <br /> <br /> <br />"'ellton-Mohawk drainage operations but, rather, it is the accumulation <br /> <br /> <br />of irrigation practices over an extended period of time. The water <br /> <br /> <br />available under the treaty is not sufficient to irrigate the present <br /> <br /> <br />acreage and maintain the proper salt balance. Even curtailment of <br /> <br /> <br />the present acreage would require that adequate leaching and drainage <br /> <br /> <br />be provided to prevent waterlogging and surface accumulation of <br /> <br /> <br />harmful salts. <br /> <br /> <br />Initially, the total quantity of dissolved solids contained in <br /> <br /> <br />Colorado River water delivered under the proposed plans will remain <br /> <br /> <br />approximately the same on an snnual basis but will be reduced as <br /> <br /> <br />refreshing of the Wellton-Mohawk aquifer progresses. If Mexico <br /> <br /> <br />carries out accepted irrigation and leaching procedures the salt con- <br /> <br /> <br />centrations will not be detrimental to the crops that are presently <br /> <br /> <br />being grown. Neither will these concentrations of salt be detrilllental <br /> <br /> <br />to soils in the irrigable classes. A number of irrigated areas in <br /> <br />'. <br /> <br />vii <br />