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<br />0[,21.89 <br /> <br />the water quality standards guaranteed to Mexico. <br />of the legislation would not be met. <br /> <br />Either way, the intent <br /> <br />The Bureau developed the program based on an assumpt~on that the average <br />annual salinity of the River at the Imperial Dam gauging point '..ould <br />remain at least at its 1974 level of about 830 parts per million. <br />However. this basic premise has not proven accurate, In 1987. the <br />salinity level actually dropped to 610 parts per mi:lion because of a <br />series of high precipitation years. When the salinity of the River is <br />low and the River's flow is at or below normal, other untreated <br />irrigation drainage sources below Imperial Dam can cause the River's <br />salinity to exceed the maximum salinity level agreed to with Mexico. In <br />such instances, water allocated to the basin states must be used to <br />offset the salinity increase caused by these other untreated sources. <br /> <br />The Bureau believes that the current low salinity level is only temporary <br />and expects that level to return to over 800 parts per million in 6 or 7 <br />years. Nonetheless, the effect of other irrigation sources when Colorado <br />Ri ver sal ini ty is low is a situation tha t was not originally presented <br />for consideration during the evaluation of program alternatives and is <br />one which could preclude the attainment of program goals, <br /> <br />ReDlacement water. The Bureau has not developed a water source to <br />replace the unrecoverable Well ton-Mohawk irrigation drainage and is <br />unlikely to do so in the foreseeable future. In authorizing the <br />desalting program, Congress assumed that a permanent new water source <br />could be found to replace the water 10stS in the operation of the <br />desalting complex. Section 101(c) of the Salinity Control Act recognized <br />r!!placement of this water during years when surplus river water was <br />unavailable as a "national" rather than a basin stat.e's obligation and. <br />authorized the Bureau to identify and develop a replacement source. A <br />June 1980 Bureau study of such sources, however, made no recommendat~on <br />in this regard. and very little progress has been :Dade since then to <br />obtain a replacement source, To date, any potential source identified <br />has been claimed for use by the state in which it was located. Thus the <br />Bureau has been left with no foreseeable way to comply with this <br />legislative requirement. <br /> <br />Gii~ <br />~Tf~y <br /> <br />Without a replacement source, water will be lost to the basin states <br />whenever the desalting plant is operated. If all 108,000 acre-feet of <br />Wellton-Mohawk irrigation drainage are desalted to meet United States <br />commitments to Mexico, about 29,000 acre-feet of the states' allocated <br />water will have to b.e used to replace the water which :Dust be diverted to <br />the Santa Clara Slough. In spite of considerable Federal investment, the <br />goal of undisturbed state water allocations is not likely to be attained. <br /> <br />SOnly 70 percent of the water which enters the desalting plant can be <br />saved, The remaining water, carrying most of the sa:t, will be disposed <br />of down the drainage canal to the Santa Clara Slough in Mexico. <br /> <br />) <br /> <br />8 <br />