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<br /> <br />the water quality standards guaranteed to Mexico. Either way, the intent <br />of the legislation would not be met. <br /> <br />o <br />c.o <br />0)" <br />CO <br /> <br />The Bureau developed the program based on an assumption that the average <br />annual salinity of the River at the Imperial Dam gauging point would <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 perts per million because of a <br />series of high precipicacion years. When the salinity of the River is <br />low and the River's flow is at or below normal, other uncreaced <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 />River salinity is low is a situation that 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 />Reolacemenr water. The Bureau has not developed a water source co <br />replace the unrecoverable Wellton-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 sourc.e <br />could be found to replace . the water 10st5 in the operation of the <br />desalting complex. Section 101(c) of the Salinity Control Act recognized <br />replacement of this wacer during years when surplus river water was <br />unavailable as a "national II rather than a basin seat.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 recommendation <br />in this regard, and very little progress has been made 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 />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 />Well ton-Mohawk irrigation drainage are desalted to meet United States <br />commi t:IIlents to Mexico, about 29,000 acre - feet of the states' allocated <br />water will have to be used to replace the water which muse be diverted co <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 />50nly 70 percent of the water ;"hich enters the desalting plant can be <br />saved. The remaining water, carrying most of the salt, will be disposed <br />of down the drainage canal to the Santa Clara Slough in Mexico. <br /> <br />8 <br />