VARIATIONS OF TURBIDITY AND NUTRIENTS IN THE TALLAPOOSA AND CHATTAHOOCHEE WATERSHEDS OF WEST GEORGIA: DETERMINATION OF THE RELATIONSHIP TURBIDITY HAS WITH FLOW, RAINFALL, WATERSHED COVER, AND HUMAN ACTIVITIES

The Tallapoosa and Chattahoochee river systems of west Georgia and east Alabama are undergoing environmental stress because of development, water withdrawals for drinking water supply, discharge of treated sewage, and usage of two reservoirs in Alabama for peak power generation. Two problems are excess sediment and nutrients that enter streams and tributaries after major rains. Excessive nutrients and sediment can be harmful to our drinking water supplies and fill in drinking water reservoirs. Our research goals are (1) to determine the relationship of turbidity (sediment) with flow and rainfall and (2) to estimate how long it will take sediment to fill up reservoirs on the rivers.

We have sampling sites on the Tallapoosa, Little Tallapoosa, and Chattahoochee Rivers, and Central Campus Branch (a small stream on the UWG campus). By collecting turbidity and nutrient data for one year we plan to predict the rate at which future water supplies will be affected by sediment and nutrient runoff. Sample sites are tested 5 days a week at 12 to 24 hour intervals for turbidity and tested twice a month for nutrients using EPA approved methods. During periods of high turbidity, 1000mL settling tubes are used to measure the level of sedimentation. Results show that the size of the drainage basin has a direct effect on how quickly turbidity increases and decreases during periods of rainfall. Small basins tend to be affected by sediment runoff faster than large basins, but they also recover faster. Minimum, median, and maximum turbidity for each sample site is as follows: the Tallapoosa River 5.2, 11, 180 NTU, the Little Tallapoosa River 5.8, 11, 150 NTU, the Chattahoochee River 3.4, 6.8, 150 NTU, and Central Campus Branch 1.2, 3, 180 NTU. The correlation between flow and turbidity has been more consistent than the correlation between rainfall and turbidity. For the Chattahoochee River the r-squared value for flow and turbidity is 0.83. The smaller basins show less correlation between flow and turbidity. The three sampling sites in the Tallapoosa watershed indicate that local variations in rainfall can cause the Tallapoosa and Little Tallapoosa Rivers to have dissimilar turbidity readings on the same day.