Hydraulic Characterization of the Upper Floridan Aquifer in the Chickasawhatchee Swamp, Southwestern Georgia

Abstract

The Chickasawhatchee Swamp is an expansive palustrine wetland located primarily in western Dougherty, eastern Calhoun, and northern Baker Counties, Georgia, in the Dougherty Plain district of the Coastal Plain physiographic province. The Chickasawhatchee Swamp is underlain by a shallow carbonate aquifer that may have a pronounced effect on the hydrologic signature of the wetland. The Swamp likely functions both as a groundwater recharge area and as a groundwater discharge area for the Upper Floridan aquifer. In the wetlands, the shallow aquifer is overlain by poorly drained swamp-alluvial soils, however, in areas where erosion has removed the overburden the carbonate rocks that comprise the aquifer are exposed. Nine wells tapping the Upper Floridan aquifer were installed in a spatially distributed pattern over the western part of the Swamp. A conceptual aquifer framework was developed and single-well aquifer tests were conducted. Each well was pumped at a low, intermediate, and high pumping rate that ranged from about 5 to 60 gallons per minute to evaluate yield characteristics, well efficiency, and aquifer response. Test results indicate the transmissivity ranges from about 1,140 to 21,300 square feet per day over the study area. The calculated transmissivity did not vary significantly between the three pumping rates which indicates that aquifer response is linear and that low volume, single-well pumping tests conducted in small-diameter wells can be used to develop representative estimates of aquifer transmissivity.