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Surface-water-quality data were collected in 1999 at 30 sites in the lower Tennessee (LTEN) River Basin in Tennessee and Alabama as part of the National Water-Quality Assessment (NAWQA) Program. One goal of the LTEN NAWQA project is to assess the effect of land use on the water quality of receiving streams in the basin. Out of 30 sites, 26 sites drain watersheds smaller than 100 square miles, and were selected to represent a gradient of land uses. The remaining sites on the Elk, Duck, and Flint Rivers, and the main stem of the Tennessee River drain larger watersheds. Water samples were analyzed for several nutrients and for fecal indicator bacteria, fecal coliform and E. coli (Esherichia coli). Sample frequency varied from weekly to semiannually depending upon site type.
Excessive nutrient loadings to steams can produce a variety of problems including degradation of aquatic habitat, excessive plant growth in reservoirs located on the main stem and tributaries of the Tennessee River, degradation of recreational quality of water, and additional water-treatment costs for drinking water. The three nutrients of most concern are phosphorus, ammonia, and nitrate. Primary sources of nutrients within the LTEN River Basin are row-crop agriculture, livestock operations, and septic systems. Where both base flow and runoff samples were collected, total phosphorous was typically higher in runoff samples. Phosphorous concentrations in base flow ranged from less that 0.01 to 0.48 milligrams per liter (mg/L), whereas concentrations in storm runoff ranged from 0.03 to 1.95 mg/L. The two highest concentrations were measured in samples collected from the Duck River near Hurricane Mills, Tennessee, and may be attributed to natural sources of phosphorus. Nitrate in base flow samples ranged from less than 0.05 to 6.52 mg/L, whereas concentrations in storm-runoff samples ranged from 0.39 to 3.29 mg/L. The highest concentrations of nitrate were at Scarham Creek near McVille, Alabama. Potential sources include confined-animal operations and septic systems. Concentrations of ammonia ranged from less than 0.02 to 0.15 mg/L in base flow, and from less than 0.02 to 0.61 mg/L in storm-runoff samples. The highest concentrations of ammonia occurred at Hester Creek near Plevna, Alabama, a tributary to the Flint River.
Sources of fecal bacteria within the LTEN River Basin include confined-animal operations and septic systems. Fecal coliform and E. coli colony counts were compared statistically and were highly correlated (r = 0.99); fecal coliform colony counts were slightly higher than E. coli colony counts. Colony counts at many sites frequently exceeded primary body-contact criteria for recreational waters during both base flow and runoff conditions; however, these counts were taken from single samples (state reporting requires a geometric mean of at least 10 samples collected over a 30-day period). Fecal coliform colony counts in base flow samples ranged from less than 1 to 1,900 colonies per 100 milliliters; colony counts in runoff samples ranged from 230 to more than 240,000 colonies per 100 milliliters.
U.S. Department of the Interior, U.S. Geological Survey
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