Regional Effect of Pumping Ground Water from Deep Fracture Systems in the Conyers Area, Rockdale County, Georgia

A 72-hour aquifer test was conducted to investigate the yield and interconnectivity of deep fracture systems in the City of Conyers, Rockdale County, Georgia. Wells tapping the deep fracture systems in the underlying igneous and metamorphic crystalline rock have yields ranging from 100 to 350 gallons per minute and can be pumped on a continuous basis. During the test, drawdown in excess of 30 feet was observed at distances as much as 6,200 feet from a pumped well and in observation wells located in two separate topographic basins. The regional effect of pumping is substantial and indicates that wells tapping deep subhorizontal fracture systems can reverse the natural (unstressed) hydraulic gradient and produce large influence areas around the pumped well. Wells tapping into the same (or similar) zones may interfere with each other, even across large distances, causing decreased well yield. Understanding the hydrologic characteristics of subhorizontal systems is critical in managing the water resource in these types of geologic settings.