CHARACTERIZATION OF PREFERENTIAL SUBSURFACE FLOW PATHS IN A MANTLED KARST TERRAIN

Disputes have persisted for nearly four decades over water resources in the Apalachicola-Chattahoochee-Flint (ACF) River Basin of the Southeastern United States. Agricultural extraction of groundwater from the Upper Floridan Aquifer (UFA) causes water shortages, shifts from perennial to intermittent streamflow, and prolonged low-flow and no-flow durations in surface streams. These changes in the streamflow adversely impact stream ecosystems that are dependent on that streamflow and has reportedly caused declines in marine fisheries. Within the ACF Basin, groundwater extraction is expected to increase from 3.9 million m³/day in 2020 to 4.3 million m³/day by 2050. Recently, researchers have pinpointed areas thought to be locations of focused recharge (hot spots) to the UFA and have used this knowledge to inform decisions related to forest management and restoration. However, how these hot spots are connected to the subsurface flow system is poorly known. Identification of preferential flowpaths in the subsurface that link recharge to discharge points could guide the implementation of center-pivot irrigation systems designed to provide water to crops while minimizing the impacts on surface streams and the ecosystems. Additionally, these results would benefit land management and groundwater modeling projects tasked with improving sustainability of the aquifer.

The Jones Center is 29,000 acres of minimally disturbed (natural) lands that are surrounded by central pivot irrigation, which makes it an ideal study area to the link between recharge features and discharge features, and to characterize the drainage framework of this mantled karst terrain. Geophysical techniques (GPR, ERT, and Lidar) that have not been tested extensively in mantled karst terrains with thick vegetative and overburden similar to the Dougherty Plain have been integrated with lithologic data from well logs and local geologic publications to characterize the subsurface preferential flow paths (solutionally enlarged fractures and conduits) and how those subsurface features connect recharge to discharge areas (landscape connectivity).