Mapping Groundwater Discharge Using Radon-222 on the Bull River, Savannah, Ga
The goal of our research was to determine the locations and fluxes of submarine groundwater discharge to the Bull River and smaller nearby creeks including Oyster Creek and Lazaretto Creek. We surveyed the river for three days from June 10th to June 12th, 2014. We used a commercially available radon detector (RAD-7, Durridge, Inc.) and a water quality meter (EXO1, YSI, Inc.) to continuously survey surface water in the estuary via boat. Slow surveying (approximately 2 kph) allowed us to detect radon-222, an indicator of recent groundwater discharge, in the estuary. We surveyed the area within three hours of low tide, when groundwater flow to the estuary was maximized. Our radon data was integrated over five-minute intervals, giving our dataset a spatial resolution of 53 m to 500 m, depending on boat speed. We used a non-steady state mass-balance box-model to calculate fluxes of submarine groundwater discharge to the estuary. We found variable fluxes from 1 m^3/day to 2056 m^3/day along approximately 50 km of surveyed shoreline. We also quantified groundwater end members by collecting nine 250 mL samples of groundwater with a peristaltic pump and push-point piezometer from beaches in the study area. These nine samples were collected from actively flowing discharge areas such as those with wet mud and rivulets. These samples had concentrations of radon-222 that ranged from 213 Bq/m^3 to 3824 Bq/m^3. To our knowledge, this is the first study near Savannah, Georgia to quantify submarine groundwater discharge to the area’s estuaries. Our findings will be helpful for people or agencies interested in the coupled nature of water resources and wildlife in estuaries. For example, data from our project can be used in future studies to determine how tidal variations affect groundwater flux and how groundwater discharge impacts wildlife along Georgia’s coasts.
Georgia Undergraduate Research Conference (GURC)
Mahaffey, Cody, Jacque L. Kelly.
"Mapping Groundwater Discharge Using Radon-222 on the Bull River, Savannah, Ga."
Geology and Geography Faculty Presentations.