SEASONAL VARIATIONS OF TOTAL PHOSPHORUS IN STREAMS AND TRIBUTARIES OF HEARD AND CARROLL COUNTIES, GEORGIA

Total phosphorus inputs have increased since the 1950s because of the use of phosphate in fertilizer and detergents. Use of phosphate detergents ended voluntarily in 1994. Total phosphorus concentrations in raw wastewater effluent contained approximately 3 mg/L of total phosphorus during the 1940s and increased to approximately 11 mg/L by the 1970s during the height of phosphate detergent use and have currently declined to about 5 mg/L. High levels of phosphorus can cause increased turbidity of streams and eutrophication in lakes. Eutrophication effects are increased aquatic plant growth and algal growth in lakes and ponds. The United States Environmental Protection Agency (USEPA) established recommended total phosphorus limits for streams that enter lakes of 0.05 mg/L and for total phosphorus in flowing waters of 0.10 mg/L. A study of 928 basins around the nation found that 90 percent of forested stream water had a median total phosphorus concentration of 0.018 mg/L (Litke, 1999). This yearlong study (West Georgia Watershed Assessment) covers 38 streams and 70 sample stations in west Georgia. The total phosphorus stream data are the results of 1,960 water samples collected at surface water sites across Carroll and Heard Counties. The area contains point source and non-point source phosphorus loading in mostly rural areas, with lesser contribution from cities and towns. Land usage for Carroll and Heard Counties is predominantly agricultural; these areas have many fields of cattle and poultry farms. Most of the streams meander through the farms and wooded areas. Effects of point sources are apparent along the Little Tallapoosa River (Carroll County), with total phosphorus increasing downstream of wastewater spray fields and again below a landfill (average doubles from 0.40 to 0.88 mg/L), followed by dilution downstream. The New River in Heard County is affected by discharge from a wastewater treatment plant and urbanization in a neighboring county east of the study area (levels range from 0.01 to 1.46 mg/L). Total phosphorus levels in this assessment lie from 0 to 6 mg/L.