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<br />o <br />.':") <br />~... <br />00 <br />,:J <br />C) <br /> <br />3. Shall consider use and value of waters fol' public water supplies, <br />propagation of fish and wildlife, recreational, agricultural, <br />industrial, and other purposes, and navigation, <br /> <br />This language is especi.ally pertinent since Colorado River Basin States are <br />presently considering changes in water quality standards, It implies that <br />there are two base conditions which we must consider: (1) Water quality <br />levels necessary to protect existing uses must be attained and maintained; <br />and (2.) As a minimum, existing quality must be maintained, and where pos- <br />sible, water quality should be enhanced. <br /> <br />It has been f"recast that, unless preventative action is taken, salinity <br />concentrations at Imperial Dam will exceed 1250 ppm as a result of future up- <br />stream development. Water in the range of 1000-2000 ppm may have adverse <br />effects on crops, and requires careful management practices when used for <br />irrigation in arid areas. 2 Similarly, the United States Public Health Service <br />Drinking Water Standards recommend that a level of 500 ppm of TDS not be <br />exceeded in public water supplies, and the discussion (pp. 32-33) indicates <br />that many residents are dissatisfied with community water supplies when salinity <br />levels reach the range of 500 to 1750 ppm. Thus it appears that both of these <br />conditions point to support for the policy that has been adopted - maintenance <br />of exIsting quality. <br /> <br />ThIs means that an action program, such as that developed by the Depart- <br />ment of the InterIor must be implemented i.f the State-Federal policy is to be <br />achIeved. <br /> <br />The foregoIng discussIon Identi.fIes a thIrd critical factor outside (l.n this <br />case I downstream from) the stream reach we are considering which may be critical <br />to determination of the requIrements imposed on discharges in that reach, To <br />restate, the maximum total load of pollutants which it is permiSSible to discharge <br />may be determined by allocation based on a maximum permissible loading for some <br />downstream reach. <br /> <br />As we look to the future, there are other critIcal needs. The Act anticipates <br />improvement in water quality. Improvement would normally result from upgrading <br />of the discharge requirements from best practicable to best available. As a practical <br />matter, however, such gains will be offset 1) by new pollution sources; 2) by ex- <br />pansion of existing sources; and 3) by flow depletions which reduce the volume of <br />water in the receiving stream. <br /> <br />Our water policies work to make the latter factors criticaL We have tradition- <br />ally attempted to supply water in accordance wIth water demands for a once-through <br /> <br />2 II Report of the National Technical Advisory Committee on Water Quality <br />Criteria, April 1968, p. 170; GPO No. 0.-287--250; 1968, <br /> <br />5 <br />