THE CHATTAHOOCHEE RIVER IN CARROLL COUNTY, GEORGIA: HOW VARIATIONS IN SUPPLY AND DEMAND, RAINFALL, AND SEASONALITY CAUSE VARIATION IN WATER QUALITY

The Chattahoochee River is a river with unusually high demands placed upon it. Its headwaters make up the smallest drainage area to provide a major portion of water supply for any metropolitan area (Atlanta, Georgia) nationwide. Demand for water has greatly increased due to growth in population (increase of over one million people from 1990 to 2000) and industry coupled with the ongoing five-year drought in this region. Water withdrawn from the Chattahoochee River and Lake Lanier (the largest reservoir on the river upstream of Atlanta) by metro Atlanta has increased from an average daily withdrawal of 331 million gallons per day (mgd) in 1990 to 429 mgd in 2001. Projected maximum withdrawals from the Chattahoochee River and Lake Lanier that can safely be done are projected to reach 705 mgd in 2030. Today’s increased demand is expected to cause a higher degradation in water quality with increased fecal coliform bacteria, turbidity, water temperature, specific conductivity, and nutrients from the 250 mgd of treated wastewater released daily from the 159 municipalities and industries discharging directly into the Chattahoochee River.

To better assess water quality downstream of Atlanta, nine water quality parameters (pH, dissolved oxygen, turbidity, specific conductivity, water temperature, fecal coliform bacteria, total phosphorus, nitrite-nitrate-N, and ammonia-N) were measured at a site 35 miles southwest of Atlanta, at the McIntosh Reserve in Carroll County, Georgia. Carroll County is a mostly rural county with pockets of urban and suburban areas in the Piedmont of west Georgia, with forest and pasturelands as the dominant land cover. The Chattahoochee River in Carroll County partially supports its designated usage as a fishing stream due to fecal coliform bacteria and fish consumption guideline (due to PCBs) violations. Samples were taken on a weekly basis starting in the summer of 2002. The study concentrates on the complex effects of rainfall and seasonal variations with water quality parameters of the Chattahoochee River. Compared to typical streams in Carroll County the Chattahoochee River in the summer has lower dissolved oxygen, higher temperature, and 4-5 times greater specific conductivity.