Effect of watershed subdivision on simulation runoff and fine sediment yield

The objective of this study was to establish the subwatershed size dependency of the Soil and Water Analysis Tool (SWAT) erosion model to adequately simulate annual runoff and fine sediment (< 0.063 mm) from the 21.3 km(2) Goodwin Creek Watershed (GCW). Results of the GCW application show that runoff volume is not appreciably affected by the number and size of subwatersheds. However an upper limit to subwatershed size is required to adequately simulate fine sediment yield produced from upland sources. Decreasing the size of subwatersheds beyond this threshold does not substantially affect the computed fine sediment yield. The proper identification of this threshold size cart optimize input data preparation requirements and computational resources needed for effective utilization of the SWAT model, and simplify the interpretation of results.