Title

Survey of the Bull River, Savannah Ga: Mapping Groundwater Discharge Using Radon-222

Document Type

Presentation

Publication Date

Fall 2014

Abstract

The goal of our research was to determine the locations and fluxes of submarine groundwater discharge (SGD) to the Bull River and nearby Oyster Creek and Lazaretto Creek. We surveyed the river from June 10-12th, 2014. We used a commercially available radon detector (RAD7, Durridge, Inc.) and a water quality meter (EXO1, YSI, Inc.) to continuously survey surface water in the estuary via boat. Slow surveying (~2 kph) allowed us to detect radon-222, an indicator of recent SGD, 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 data set a spatial resolution of 53--500 m, depending on boat speed. Our groundwater fluxes were variable, ranging from 1-2056 m^3/day along ~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 actively flowing discharge areas such as those with wet mud and rivulets in the study area. These samples had radon-Â-222 concentrations that ranged from 213-3824 Bq/m^3. To our knowledge, this is the first study near Savannah, Georgia to quantify SGD to the area’s estuaries. Our findings will be useful for understanding how seasonal tidal variations impact groundwater fluxes and how SGD impacts wildlife along Georgia’s coasts.

Sponsorship/Conference/Institution

Southeastern Estuarine Research Society Fall Meeting (SEERS)

Location

Carolina Beach, NC