SEDIMENT, FECAL COLIFORM BACTERIA, AND NUTRIENTS IN STREAMS OF WEST GEORGIA: CONTRIBUTIONS OF BASEFLOW, WETFLOW, AND STORMFLOW

Streams in the Piedmont province of Georgia, because of topography, deep weathering, and human activities are subject to a sudden influx of sediment, fecal coliform bacteria, and nutrients (ammonia-N, nitrite-nitrate-N, and total phosphorus) during rain events. Sediment is such a persistent problem in non-forested watersheds and in forested watersheds after clear cutting in the southeastern United States that after rain events streams turn blood red in color as turbidity and total suspended sediment increase 1000-fold. High sediment load damages stream habitat, chokes the channel, interferes with recreational uses, carries additional pollutants such as bacteria, nutrients, and metals, and increases the cost of water treatment and the potential of harmful chlorine byproducts in treated water.

Our research is in the Chattahoochee and Tallapoosa River basins of west Georgia. Data collection from 1988 to 2001 was weekly to monthly water quality monitoring from one to two years in watersheds of various degrees of disturbance. During 2002 and 2003, 12-hour interval sampling was added to determine what is truly baseflow and stormflow. Some streams after the stormflow peak require long time spans (days to weeks) to return to baseflow after a major rain. Wetflow has been added as an additional stage of stream flow. Wetflow is the flow region after the stormflow peak(s) and before baseflow is reached. Data collection during the very wet 2002-2003 shows that periods of baseflow can be rare and that stormflow and wetflow may extend for months. Additional results are that samples taken from altered watersheds during stormflow may show large increases in ammonia-N followed by declines during wetflow; some so-called wet events (0.1 to 0.2 inches of rain) in forested watersheds do not alter water quality parameters because of the effective infiltration of rainwater; streams with point source discharge of treated sewage and urban runoff have step ups in nutrients, fecal coliform, and sediment; improvements in sewage treatment methods and a 1990 ban on phosphate detergents in Georgia have lowered ammonia and phosphate but have not altered the continuing increase in nitrite-nitrate-N; and runoff from farmland (cattle pasture and excessive spreading of chicken litter) and septic systems can cause spikes in pollution during stormflow.