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Show H Summary of Major Findings 50 KILOMETERS The Great Salt Lake Basins Study Unit encompasses about 14,500 square miles and includes parts of northeastern Utah, southeastern Idaho, and southwestern Wyoming. The Study Unit comprises three major river systems that enter Great Salt Lake: the Bear, Weber, and Utah Lake- Jordan River systems. About 1.7 million people, or about 76 percent of the population in the State of Utah, live along the western flanks of the Wasatch Mountains in the Salt Lake City, Ogden, and Provo metropolitan areas. Stream and River Highlights Surface water sampled in the Great Salt Lake Basins Study Unit generally meets existing guidelines for drinking water and protection of aquatic life. Urban, agriculture, and mining land uses have affected water quality, as indicated by elevated concentrations of pesticides, volatile organic compounds ( VOCs), nutrients, chloride, and trace elements in basins dominated by these land uses. • Water development and management have degraded the chemical and biological quality of some streams. Water of good quality in headwater areas often is diverted before reaching lower stream reaches known for poorer quality. Streams with minimal flow have elevated concentrations of nutrients, warm temperatures, and reduced habitat cover, which are difficult conditions for fish and other aquatic organisms to survive. ( See pages 6 and 7) Selected Indicators of Stream Water Quality Small Streams Pesticides Nitrate Total phosphorus Trace elements in sediment1 Trace elements in tissue1 Organochlorines in sediment3 Organochlorines in tissue3 Major Rivers iirKan Agricul- Unde- Mixed uroan turg| veloped Land Uses II Hj Proportion of samples with detected concentrations greater than or equal to national drinking- water standards and guidelines, guidelines for protection of aquatic life or wildlife, or the national goal for preventing nuisance plant growth EMJ Proportion of samples with detected concentrations that do not exceed drinking- water standards and guidelines, guidelines for protection of aquatic life or wildlife, or the national goal for preventing nuisance plant growth I I Proportion of samples with no detections 1 Arsenic, mercury, and metals. 2 Insufficient data. 3 Organochlorine compounds, including DDT, PCBs, and chlordane. • Concentrations of nitrogen were about 3 to 4 times higher in urban, agricultural, and mixed land- use settings than in undeveloped basins. Phosphorus concentrations exceeded the U. S. Environmental Protection Agency ( USEPA) desired instream goal of 0.1 mg/ L ( milligram per liter) for preventing nuisance plant growth in 12 of 27 streams sampled. ( See page 10) • Pesticides are widespread, detected in about 95 percent of the streams sampled. Concentrations of carba- ryl, diazinon, and malathion exceeded guidelines for protection of aquatic life. Aquatic- life guidelines have been established for only 18 of the 49 pesticides detected. Pesticide concentrations were generally lower in streams in undeveloped and agricultural areas than in streams affected by urban land uses. ( See pages 12 and 13) • Of the 27 organochlorine compounds for which samples were analyzed, 12 were detected in fish tissue and 6 in streambed sediment. Two commonly detected compounds were PCBs and DDT. In fish samples, PCBs were detected at 8 sites, DDT at 13 sites. In sediment, PCBs were detected at two sites, and DDT compounds at four sites. Guidelines for fish- eating wildlife were |