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Woodside, M.D., Hoos, A.B., Johnson, G.C., and Treece, M.W., 1999, Yields of total nitrogen and total phosphorus in the Tennessee River Basin, 1992, in Mississippi Water Resources Conference, Raymond, Mississippi, 1999, Abstracts, p. 46
Nutrient enrichment can disrupt the ecological balance of streams, lakes, and reservoirs. As part of the U.S. Geological Survey's National Water-Quality Assessment Program, yields of total nitrogen and total phosphorus were estimated for numerous basins, ranging in size from 49 to 40,330 square miles, in the Tennessee River Basin. Spatial variation in yields of total phosphorus and total nitrogen were related to natural sources and land uses. Yields were calculated for the 1992 water year using nutrient loads which were estimated by use of a seven-parameter log-linear regression model. For basins with insufficient nutrient data for 1992, nutrient loads were estimated for a year that was hydrologically similar to 1992.
In 1992, the median yield of total nitrogen was 1.28 tons per square mile (tons/mi2) for 42 basins in the Tennessee River Basin. Yields of total nitrogen ranged from 0.02 tons/mi2 in the Ocoee River Basin near Parksville, Tennessee, to 3.50 tons/mi2 in the Town Creek Basin near Geraldine, Alabama. The Ocoee River Basin is predominantly forested land, thus the contribution to total nitrogen from nonpoint sources is small. Estimated wastewater inputs into the Town Creek Basin comprise less than 1 percent of the yield of total nitrogen. Nonpoint inputs from confined-animal operations and crop production are the largest potential sources of nitrogen in the Town Creek Basin.
In 1992, the median yield of total phosphorus was 0.05 tons/mi2 for 36 basins in the Tennessee River Basin. Yields of total phosphorus ranged from less than 0.02 tons/mi2 in the Ocoee River Basin near Parksville, Tennessee, to 1.14 tons/mi2 in the Duck River Basin above Hurricane Mills, Tennessee. Yields of total phosphorus from the Duck River Basin were much higher than yields from the other 34 basins where yields were less than 0.5 tons/mi2. Naturally occurring phosphatic limestone in the Duck River Basin contributes to high yields of total phosphorus; estimated wastewater inputs comprise less than 3 percent of the yield of total phosphorus.
U.S. Department of the Interior, U.S. Geological Survey
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