NUTRIENT MASS BALANCE FOR THE ALBEMARLE-PAMLICO DRAINAGE BASIN, NORTH CAROLINA AND VIRGINIA, 19901

Authors

  • Gerard McMahon,

    1. Respectively, Geographer, U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, North Carolina 27607; and Hydrologist, U.S. Geological Survey, 3600 West Broad Street, Richmond, Virginia 23230.
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  • Michael D. Woodside

    1. Respectively, Geographer, U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, North Carolina 27607; and Hydrologist, U.S. Geological Survey, 3600 West Broad Street, Richmond, Virginia 23230.
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  • 1

    Paper No. 96055 of the Journal of the American Water Resources Association (formerly Water Resources Bulletin). Discussions are open until December 1, 1997.

Abstract

ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and phosphorus and watershed nitrogen retention and processing capabilities. Basin total nitrogen and phosphorus input estimates were calculated for atmospheric deposition (which averaged 27 percent of total nitrogen inputs and 22 percent of total phosphorus inputs); crop fertilizer (27 and 25 percent); animal-waste (22 and 50 percent, respectively); point sources (3 percent each of total nitrogen and total phosphorus inputs); and biological nitrogen fixation (21 percent of total nitrogen inputs). Highest in-stream nitrogen and phosphorus loads were measured in predominantly agricultural drainage areas. Intermediate loads were observed in mixed agricultural/urban drainage areas; the lowest loads were measured in mixed agricultural/forested drainage areas. The difference between the sum of the nutrient input categories and the sum of the in-stream nutrient loads and crop-harvest nutrient removal was assigned to a residual category for the basin. The residual category averaged 51 percent of total nitrogen inputs and 54 percent of total phosphorus inputs.

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