Nutrient data from the Santee River Basin and coastal drainages study area were assessed for 1973-93 as part of the U.S. Geological Survey National Water Quality Assessment Program. Data sources include the U.S. Geological Survey National Stream-Quality Accounting Network and the U.S. Environmental Protection Agency Storage and Retrieval of U.S. Waterways Parametric Data databases. Specific nutrient species chosen for assessment were total ammonia nitrogen, nitrite-plus-nitrate nitrogen, total Kjeldahl nitrogen, and total phosphorus.

The study area was divided into four subunits: the Broad, Catawba, Cooper, and Edisto. Nutrient concentrations were generally higher in the Broad and Catawba subunits, where some stations were influenced by point-source discharges, than in the Cooper and Edisto subunits. Nitrite-plus-nitrate nitrogen showed the greatest seasonal variation of the nutrients assessed.

Nonpoint-source nutrient contributions to the study area include atmospheric input and fertilizer and manure applications. Atmospheric ammonia nitrogen and nitrate nitrogen inputs were determined using data from four National Atmospheric Deposition Program/National Trends Network stations. Nonpoint-source loads of nitrogen were higher from atmospheric sources than from fertilizer or manure applications. Nonpoint-source loads of nitrogen and phosphorus were higher from fertilizer applications than from manure applications.

Nutrient loads being carried by streams were estimated at four stations in the Broad River basin and three stations in the Saluda River basin. Concurrent streamflow and water-quality data were available for at least 13 years. Monthly and annual median loads were calculated for each of the seven stations for ammonia nitrogen, nitrite-plus-nitrate nitrogen, total Kjeldahl nitrogen, and total phosphorus, and spatial comparisons were made between loads. Nonpoint-source agricultural and atmospheric contributions were also estimated for the drainage basins of the seven stations.

--- August 1997

To order SANT NAWQA publications, please email or call:

Celeste A. Journey
SANT NAWQA Project Chief
cjourney@usgs.gov
(803) 750-6141