Comparison of Radon-derived Groundwater Discharge Fluxes From Georgia Tidal Creeks

Presentation given at the Georgia Water Resources Council.

Groundwater discharge fluxes are known to be spatially and temporally variable. They are also known to impact the biology of the receiving areas. We have been studying these variations, in addition to water chemistry to assess potential correlations between groundwater discharge and eastern oyster (Crassostrea virginica) beds. We collected groundwater and estuary samples from four recreational oyster harvesting creeks along the Georgia coast. Oyster Creek near Tybee Island, Jointer Creek near Jekyll Island, Medway River between Ossabaw and St. Catherines Islands, and Teakettle Creek near Sapelo Island were surveyed between July and October 2018. We collected groundwater samples using peristaltic pumps connected to push-point piezometers driven to ~50 cm depth at locations above the low-tide line from each creek bank. Groundwater discharge was surveyed using a commercially available radon detector (RAD-7), which monitors for radon-222, a well-established tracer of groundwater discharge. In the lab, we diluted, filtered, and analyzed the samples using ion chromatography. We found that the amount of groundwater discharge varies within each creek. Water quality and nutrient concentrations will be compared to oyster data that was collected simultaneously with the groundwater data to evaluate the relationship between oyster health and groundwater discharge sites in Georgia's recreational harvest areas.