DISSOLVED AND SUSPENDED-SOLIDS TRANSPORT FROM COASTAL-PLAIN WATERSHEDS

Excessive amounts of dissolved or suspended solids in surface runoff or base flow may degrade the quality of streams, lakes, or other water bodies. Loads of dissolved and suspended solids in streamflow reflect the quality of water entering via surface runoff or base flow. This study was conducted to determine the concentrations and loads of dissolved and suspended solids in Coastal Plain streamflow; to examine relationships between concentrations, loads, and flow rate; and to determine overall streamflow water quality for these parameters. Dissolved solids and suspended sediment concentrations were determined on weekly or high-flow storm event streamflow samples collected at gaging stations on three subwatersheds (B, 334.3 km2; F, 114.9 km2; and K, 16.7 km2) of the Little River Watersheds located near Tifton, GA. Dissolved solids concentrations ranged from 19 to 159 mg L-1, and generally decreased as per unit area instantaneous discharge rate increased. Suspended sediment concentrations ranged from 1 to 137 mg L-1, and generally increased as per unit area instantaneous discharge rate increased. Regression analyses showed good relations between log transforms of both dissolved solids load (r2 = 0.97) and suspended sediment load (r2 = 0.79), vs. total monthly runoff. Mean suspended sediment concentrations during high-flow events were greater than means from the overall data set, while mean concentrations of dissolved solids from these events were reduced relative to the overall data set. The study showed that dissolved solids are the major component of total solids in Coastal Plain streamflow. The mean dissolved and suspended sediment concentrations during the study were 67, 60, and 51 mg L-1; and 14, 17, and 14 mg L-1 for Watersheds B, F, and K, respectively. Overall, the study showed that, as measured on these watersheds, Coastal Plain streamflow is of good quality in terms of both dissolved and suspended solids. This good quality may reflect land-use practices designed to prevent soil erosion, but primarily reflects the Coastal Plain landform shape, which causes sediments eroded from the uplands to be deposited in the riparian zone before they can enter streamflow.