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PART IV COLORADO RIVER WATER QUALITY ASSESSMENT e Higher surface and ground waters tend to reduce wastewater treatment plant efficiencies. Problems associated with this are line breakage, infiltration into sewer lines through cracks or joints, excessive flow rates, and flooding of the facility. High ground water creates problems by filling septic tanks and drain fields, thus reducing the capability of sewage disposal by overloading. This may result in contaminated ground water flowing into streams. Point sources present a geographically limited problem to water quality but are obviously more significant in the highly populated areas. Wastewater treatment facilities, concentrated in certain drain- ages because of the population loads, seriously impact the receiving streams. Most water quality problems in Utah result from nonpoint sources rather than point source discharges. Nonpoint sources of pol- lutants include runoff from natural geologic formations, agriculture, urban sources, hydrologic modification, mining, septic tanks, construc- tion, and silviculture. Natural sandstone formations in eastern and southern Utah contribute significant amounts of sediments through ero- sion. Natural deposits of salts, phosphates, fluorides, nitrates, and arsenic also contribute to decreasing water quality in certain areas of the State. e Most of the water allocated in Utah is for agricultural use. As a result, this is one of the primary sources of man-induced nonpoint pollu- tion. Diversion of waters for irrigation tends to concentrate salts and solids in original stream channels. Also, return flow discharges add salts, nutrients, and sediments from croplands into stream channe Is. Overland runoff contributes salts and sediments from nonirrigated crop- lands and coliform bacteria from pasture land. Salinity will remain a problem in Utah. High runoff has decreased TDS concentrations, but increased flows have increased total loadings to the Colorado. C. Colorado e The most significant water quality problems in the basin are to maintain the existing high quality waters in streams and lakes that may be threatened by wastewater from growing communities and to rehabilitate several streams that have been contaminated by heavy metals from drain- age from inactive mine tunnels, mill wastes, tailing piles, and natural sources. Wastewater treatment plants for most communities in the basin have been expanded during the last several years to accommodate the in- creasing population brought about by growth in the recreation and energy sectors of the ~conomy. An important pollutant in domestic wastewater lS ammonia. Ammonia in the un-ionized ammonia form occurs in low con- centrations, particularly in the winter time, in several tributary streams including the Yampa, Roaring Fork, San Miguel, Fraser, and East Rivers. If population continues to grow in these basins, the un-ionized ammonia standard for aquatic life may not be met without advanced wastewater treatment levels. 18