MODELING THE HYDROLOGY OF A FORESTED CAROLINA BAY WETLAND

Geographically isolated, depressional wetlands such as Carolina Bays buffer storm event runoff and are an important component in the shallow groundwater systems of the Southeastern U.S. Coastal Plain. To test this hypothesis, we collected seven years of surface water and groundwater elevation data in a Coastal Plain watershed in South Carolina (32.88º, -81.12º) that has clay-based, forested Carolina Bays. We focused on one wetland and compared rainfall and temperature data to water-table well and piezometer data and created a conceptual model that describes the hydrology of the system under wet, dry, and drought conditions. During years of below-normal rainfall the well and piezometer data between the upland, the wetland margin, and the wetland center indicated groundwater recharge from the perched water table beneath the wetland, whereas during years of above- and near-normal rainfall, the hydraulic gradient suggested groundwater discharge into the wetland. While rainfall and evapotranspiration were the major water input and output fluxes, and groundwater flux was less than ten percent of the annual water budget, results from a distributed hydrologic model, FLATWOODS, showed that the wetland during wet time periods actually behaved as a flow-through system, likely due to landscape position and the stratigraphy and slope of the underlying sediments.