Understanding the Hydrologic Response of a Coastal Plain Watershed to Forest Management and Climate Change in South Carolina, U.S.A.
The hydrologic processes in wetland ecosystems are not well understood. There are also great concerns and uncertainties about the hydrologic response of wetlands to forest management and climate change. The objective of this study is to apply a hydrologic model to better understand the hydrologic processes of a low relief coastal forested watershed and its responses to potential land disturbance, and to test its sensitivity to potential climate variability and change. We applied MIKE SHE, a physically based and spatially distributed hydrologic model, at Watershed 80 within Santee Experimental Forest in the lower coastal plain of South Carolina, United States. With a user-friendly interface and GIS (Geographic Information Systems) linkage, the MIKE SHE model integrates surface water and groundwater, and it simulates full hydrologic cycle including interception, evapotranspiration (ET), infiltration, overland flow, subsurface and channel flow (with MIKE 11), and unsaturated and saturated soil water movement. The model was validated by the water table and streamflow data collected at the site in 2003 and 2004. Overall, the model performed well in simulating the hydrologic dynamics of the study watershed. The model simulations indicate that runoff is mainly generated by the overland flow after the soil is saturated during wet periods. We applied the validated model to examine the responses of reduction of leaf area index (LAI), increase of air temperature by 2 degrees C, and decrease of precipitation by 10%. Generally, the modeling results suggest that forest removal will raise the water table, especially during the dry periods, due to decrease in ET. Increase of air temperature or decrease of precipitation will reduce groundwater recharge and result in lower water table and runoff.