USGS geologists and hydrologists are mapping subsurface fracture systems to investigate ground-water flow in the Piedmont of Georgia and to determine the effects of these fracture systems on well yield. USGS scientists also are working northwest of Atlanta to investigate the processes that control the extent and movement of ground water contaminated with chlorinated solvents, which may endanger local ground-water resources. The quality of water is vital to support society's needs and to sustain rich and diverse ecosystems in Georgia. The USGS is studying the effects of land use on the physical, chemical, and biological quality of water. Phosphorus in the Upper Chattahoochee River During the period from 1980 to 1993, Metropolitan Atlanta's population increased by about 43 percent, thus resulting in an increase of about 50 percent in wastewater discharge to the Chattahoochee River from the six largest Atlanta wastewater-treatment facilities.
Treated wastewater is a point source of the nutrient phosphorus.
Increased phosphorus loadings can produce rapidly multiplying algal blooms that degrade the recreational, water-supply, and habitat value of streams and lakes. Even though the volume of effluent increased from 1988 to 1993, phosphorus loads from wastewater-treatment facilities decreased by about 83 percent because of reduced phosphorus concentrations in raw sewage and improved treatment methods. The annual phosphorus load at monitoring sites on the Chattahoochee River upstream and downstream from Atlanta from 1980 to 1993 is shown in figure 4 . The difference between the two curves shown on the graph indicates the effect of point and nonpoint sources from Atlanta on the phosphorus load in the River. Reductions in point-source phosphorus loads have been documented, and phosphorus loads in the river downstream from Atlanta declined by about 54 percent from 1988 to 1993.