Prediction of Surface Runoff and Soil Erosion using WEPP Model with Climate Changes in Korea.

The objective of this study was to apply and adjust CLIGEN parameter values to generate realistic precipitation and temperature change scenarios for soil erosion prediction at three different sub-watersheds of Goseong-Cheon watershed in Korea. Total area of the watershed is 514 ha, which consists of 11.8% paddy field, 4.5% upland, and 73.3% forest. CLIGEN was used to generate 100-year climate sequences with daily climate data such as temperature, precipitation, wind, and solar radiation for a representative climate station in the study site for the period 1973-2005 to predict surface runoff and soil loss with WEPP. Three climate change scenarios were used A1B scenarios, which were resulted from the coupled climate model ECHO-G by the National Institute of Meteorological Research in Korea in this study: 1) adjusting the mean amount of rainfall on a wet day, 2) adjusting the mean amount of temperature, and 3) a combination of 1) and 2). Observed mean annual precipitation at Gong-Ju (1,246 mm) was similar to CLIGEN simulated data (1,279 mm). WEPP model predicted surface runoff and soil loss in Sangwon sub-watershed were higher than that in other sub-watersheds. The combination of topography and soil characteristics strongly influenced this estimate. Climate change scenarios 3 that combined changes in precipitation depths with changes in maximum and minimum temperature showed the largest impacts on predicted surface runoff and soil loss in all sub-watersheds. Especially, a combined 17% increase in precipitation parameter and 4°C increase in temperature parameters in Sangwon sub-watershed resulted in increases of 15, 32, and 139% in generated average annual precipitation, predicted surface runoff, and predicted soil loss, respectively. Increases in rainfall and temperature due to climate change may thus in substantial and nonlinear increases in runoff and soil loss in Korea.