The U.S. Geological Survey (USGS) began a National Water-Quality Assessment Program (NAWQA) in 1991 to describe the status of and long-term trends in the quality of the Nation's surface-and ground-water resources. The study of the Santee River Basin and coastal drainages began in 1994 and includes about 23,500 square miles and covers parts of North Carolina and South Carolina. A network of sites in the study was designed according to NAWQA guidelines and ecological, surface- and ground-water sampling began in October 1995.

One of the basic fixed sites in the network is the Coosawhatchie River near Early Branch, South Carolina. The drainage area of this blackwater river at the fixed site is approximately 400 square miles. Land use in the basin is mainly agriculture (42 percent), forest (30 percent), and wetlands (24 percent). Water-quality samples were collected monthly at the site for a 2-year period. Specimens of algae, macroinvertebrates, and fish were collected and aquatic habitat was described in a 1,000-foot reach of the river. Bed sediment and native-clam tissue samples were collected near the basic fixed site. These samples were analyzed for trace elements and organic constituents.

A special study is being conducted to characterize water-quality samples for the Coosawhatchie River at the basic fixed site and at a site downstream (Coosawhatchie River near Grays, South Carolina). Surface-water data collection included samples collected in the summer (low flows) and in the winter (intermediate flows). Samples were also collected during storms (high flows). Peak discharges measured during sampling ranged from 13 to 799 cubic feet per second. At low and intermediate flows, samples were collected daily at each of the two sites for three days. Storm-flow samples were collected daily on the rising limb of hydrographs and intermittently on the falling limb. Temperature, conductivity, pH, dissolved oxygen, and alkalinity were measured in the field, and samples were collected and processed for analysis of nutrients, organic carbon, major ions, and suspended sediment. Stream discharge was measured continuously at both sites.

--- May 1997

To order SANT NAWQA publications, please email or call:

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