Assessment of Riparian Buffer Impacts within the Little River Watershed in Georgia USA with the SWAT Model

Abstract

The Soil and Water Assessment Tool (SWAT) contains a simple function to simulate riparian buffers as a function of filter strip width (FILTERW). The objectives of this study are 1) evaluate the response of SWAT hydrology and sediment components to changes in watershed subdivision and FILTERW and 2) provide guidance for selecting appropriate watershed subdivision and FILTERW values. Watershed subdivision is controlled by the Critical Source Area (CSA), used to define the minimum drainage area required to form the origin of a stream. SWAT was calibrated on a subwatershed (15.7 km2) within the Little River Experimental Watershed, Georgia, USA, and the calibrated parameter set applied to 32 different watershed configurations: four different FILTERW representations for each of eight CSAs. Streamflow predictions were stable regardless of watershed subdivision and FILTERW. Predicted sediment loads from upland areas decreased with increasing CSA. Sediment yield at the watershed outlet showed dynamic responses to different combinations of CSA and FILTERW. A subdivision level that simulates a watershed drainage density similar to the actual stream length was suggested as the upper CSA boundary.