National Water-Quality Assessment Program—Upper Tennessee River Basin Study Unit Phosphorus in Streams of the Upper Tennessee River Basin, 1970-93

• Median total phosphorus concentrations for the period 1984-93 were less than 0.1 milligrams per liter at 65 of the 83 stations evaluated in the study unit. • Highest total phosphorus concentrations were in the Hiwassee River Basin (near 2.0 milligrams per liter) and at West Chickamauga Creek near Chattanooga (1.45 milligrams per liter). • Total phosphorus concentrations have not significantly changed since 1970 at 33 of the 42 stations examined; declines in total phosphorus concentrations were detected at 8 stations. • Phosphorus concentrations decreased significantly at four of seven stations on the French Broad River after the phosphate detergent ban was imposed for North Carolina in 1988. • The Tennessee River Basin between Watts Bar Dam and Chattanooga, excluding the Ocoee River Basin, accounted for over 65 percent of the total phosphorus load for only 16 percent of the total area of the study unit. • Yields of total phosphorus were largest for the French Broad and Pigeon River Basins (1.19 and 0.88 pounds per acre per year, respectively). • Total phosphorus concentrations were highest at stations with large agriculture and urban land uses