Nitrogen in Streams of the Upper Tennessee River Basin, 1970-93

U.S. Geological Survey, Open-File Report 97-117

by M.W. Treece, Jr., and Gregory C. Johnson

This report is available as a pdf below


In 1994, the U.S . Geological Survey (USGS) began an investigation to assess water-quality conditions in the upper Tennessee River Basin. The study was implemented as part of the National Water-Quality Assessment (NAWQA) Program, which is designed to describe in a nationally consistent manner the status of and trends in the quality of a large representative part of the Nation's surface and ground-water resources and to relate assessment of status and trends to the natural and human factors that affect the quality of water. When the NAWQA Program is fully implemented, water-assessment investigations will be ongoing in 60 study units across the Nation (Leahy and others, 1990). The general concepts of the NAWQA Program were outlined in a report by Hirsch and others (1988).

The Upper Tennessee River Basin study unit (fig. 1) drains an area of about 21,390 square miles (mi^2), which includes the entire drainage of the Tennessee River and its tributaries upstream of the USGS gaging station at Chattanooga, Tennessee. The basin includes parts of four States: Tennessee (11,500 mi^2), North Carolina 5,480 mi^2), Virginia (3,130 mi^2), and Georgia (1,280 mi ). Four major river systems-Clinch/Powell, Holston, French Broad, and Little Tennessee-make up about 82 percent of the study unit . The basin includes parts of three physiographic provinces- Blue Ridge, Cumberland Plateau, and Valley and Ridge-that are areas of homogeneous climatic, geologic, and biologic characteristics.

Land use in the upper Tennessee River Basin study unit is primarily forest and agriculture. Forest covers about 64 percent of the basin, and agricultural land, which is predominantly pasture land, accounts for about 27 percent of the basin. Most of the agricultural land is located in stream valleys and the more gently rolling areas of the Valley and Ridge Physiographic Province . Urban areas, water bodies, and barren land account for the remainder of the land use in the basin.

This report presents results of analyses of available data for nitrogen concentrations in streams in the upper Tennessee River Basin. These analyses are part of the retrospective-analysis phase of the study-unit investigation and include the review and analysis of existing waterquality data to provide a historical perspective of waterquality conditions in the study unit. The information was used to assess the available data, develop the initial study design for the NAWQA project, and evaluate priorities for future water-quality research.

Statistical summaries, trend analyses, and stream loads were computed for total nitrogen, total ammonia plus organic nitrogen, and total nitrite plus nitrate (N0_2-+ N0_3-). Concentrations are reported in milligrams per liter as nitrogen, and loads are reported in pounds per day as nitrogen. Data were collected by the USGS, the Tennessee Valley Authority (TVA), and State governmental data-collection agencies in Tennessee, North Carolina, Virginia, and Georgia. All data were retrieved from the U.S . Environmental Protection Agency STORET and the USGS WATSTORE data bases.

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