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Kingsbury, J.A., 1999, Environmental setting of the lower Tennessee River Basin: the primary natural and cultural factors that affect water quality [abs.], in Crabtree, L.R., Bradley, M.W., Blunt, Tiffany, and Pierre, Salnave, comps., Tennessee Water Resources Symposium, 9th, Nashville, Tenn., 1999, Extended abstracts: American Water Resources Association, Tennessee Section, p. 2B-1.
The National Water-Quality Assessment Program was initiated to describe current water-quality conditions for a large part of the Nation's water resources, identify water-quality changes over time, and identify the primary natural and human factors that affect water quality. The water-quality assessment of the lower Tennessee River Basin study unit began in 1997. To help meet the goals of the program, geology and physiography were used to subdivide the lower Tennessee River Basin into environmental settings in which natural factors such as rock type and physical setting are similar. This subdivision establishes a baseline for water-quality data within each setting, which then allows the effects of cultural factors on water quality to be assessed. Boundaries between the environmental settings in the lower Tennessee River Basin generally coincide with Level III and Level IV ecoregion boundaries delineated in the basin.
Water-use, wastewater discharge, and agricultural-activities data were summarized by environmental settings within the basin to identify water-quality issues and to aid in the overall study design. Public-supply water use and wastewater discharges are greatest in the Eastern Highland Rim and the Nashville Basin settings within the basin. Estimated agricultural chemical use and unit-area nutrient loads from agricultural activities also were largest in these settings.
Ground- and surface-water-quality data collected between 1980 and 1996 available in digital databases (e.g. STORET and WATSTORE) were aggregated and analyzed as part of a retrospective data analysis for the project. Data for major inorganic constituents, nutrients, bacteria, and pesticides were summarized by environmental setting to determine the spatial distribution of existing data, identify any data gaps, and characterize water quality within each setting.
Surface and ground water in the basin is predominantly a calcium bicarbonate type. Specific conductance values were between 20 and 300 microsiemens per centimeter for surface-water samples and between 100 and 1,000 microsiemens per centimeter for ground-water samples. Median specific conductances were higher in areas of carbonate geology for both surface and ground water. Nitrate was the most commonly analyzed nutrient in the data set. The highest median nitrate concentrations (about 1 milligram per liter) were for surface-water samples collected from the Eastern Highland Rim, Nashville Basin, and Cumberland Plateau settings. Nitrate concentrations exceeded the maximum contaminant level of 10 milligrams per liter in less than 1 percent of about 5,500 samples collected. The highest median concentrations (about 1 milligram per liter) were for ground-water samples collected from the Eastern and Western Highland Rim and the Cumberland Plateau. The maximum contaminant level for nitrate was exceeded in 2 percent of about 3,200 samples collected.
U.S. Department of the Interior, U.S. Geological Survey
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