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WATER QUALITY - MORE THAN CHANCE By REINHOLD W. THIEME, Deputy Assistant Secretary Department of the I ntarior. Washington, D. C. It is a genuine pleasure to be here with you. Assistant Secretary Klein asked me to bringyou his greetings and to tell you how disappointed he was at not being able to speak to you in person, He is quite concerned about the Colorado, but the press of prior commitments made it impossible for him to be here. Salinity is one of the most pressing water quality problems in the Colorado River System, Like many other streams in arid regions of the Western United States, the Colorado River displays a progressive increase in salinity between its headwaters and its mouth. " The mineral quality of the Colorado River below Lees Ferry, Arizona, is approaching critical levels from the standpoint of use for irrigated agriculture, as well as for municipal and industrial water supply, Future development and depletion of the water allocated to the upper basin states will cause further increases in salinity concentrations in the Lower Colorado River, There is approximately a twenty,fold increase in dissolved solids concentration berween the Colorado's headwaters in Colorado and Imperial Dam in Arizona, the point of last major diversions in the United States. Both natural and man, made conditions contribute to the basin's salinity problems. Since mineral salts are non,degradable, the amount of salt to be transported as well as the quantity of water available to carry the salt are important factors in determining the quality of water throughout the basin, There is a clear distinction between two basic causes of salinity increases in streams in the basin. These are the salt loading and salt concentrating effects. The former is associated with the addition of mineral salts to the stream system from both natural and man-made sources. The latter occurs as a consequence of the abstraction and consumptive use of water as a result of natural conditions and man's activities. While no additional mineral salts are added to the stream system, the salt concentration increases as a consequence of loss of water from the system. Future expansion of municipal, industrial, and Irrigation actlVltles in the upper basin will be accompanied by further increases in salinity in the Lower Colorado River, '. salt loading will be increased slightly; however, increases in concentration of dissolved solids will result mainly from consumptive use and depletion of the river's water supply by the upper basin states, In the Colorado River System, the detrimental effects of salinity are confined generally to con- sumptive uses of water within the projected rise in salinity. ,17, Little or no adverse effects are anticipated for non-consumptive uses of water such as recreation, water sports, fish and wildlife, navigation, hydropower generation, and aesthetic enjoyment,