Modeling the effect of land use change on hydrology of a forested watershed in coastal South Carolina.
Since hydrology is one of main factors controlling wetland functions, hydrologic models are useful for evaluating the effects of land use change on we land ecosystems. We evaluated two process-based hydrologic models with different structures, MIKE SHE and DRAINMOD, using a 3-year (2003-05) dataset collected from a coastal South Carolina forested wetland watershed (WS80) on Santee Experimental Forest to evaluate the effects of land use change on hydrology of wetlands. The model performance was evaluated using the coefficient of determination (R2) and Nash-Sutcliffe model efficiency (E). The two models were further tested by applying them for assessing effects of land use change on streamflow and water table in WS80 under four scenarios of converting forested watershed to varying proportions of cropland, 30, 40, 50 and 100%. Simulation results showed that, for both models, the outflow proportionally increases with an increase in the fraction (0— 1.0) of agricultural land area with a rate ranging from 0.30 to 0.35. Depending on precipitation patterns, those values for a normal year represent a change in annual runoff of 64 - 69 mm for conversion from 50% of forestland to cropland, and an increase of 113 - 122 mm for a complete watershed conversion. The water table was predicted to increase by an average of 8 - 10 cm across the watershed for a complete land use conversion scenario. The change in runoff and water table due to converting forest to cropland is primarily a result of decreased evapotranspiration from croplands after conversion.