Impacts of Rainfall, Soil Type, and Land-Use Change on Soil Erosion in the Liusha River Watershed: Fid-Bau Portal

Impacts of Rainfall, Soil Type, and Land-Use Change on Soil Erosion in the Liusha River Watershed

Zhang, Shanghong / Li, Yueqiang / Fan, Weiwei / Yi, Yujun

To assess the impacts of rainfall and land-use changes on soil erosion, the Liusha River watershed in China was chosen as a case study for its representative topography and climate. Investigations were conducted using the soil and water assessment tool (SWAT) model and maps of land-use and soil types, together with meteorological data from six gauging stations. The Nash-Sutcliffe efficiency $E_{n s}$ (0.84 and 0.75), correlation coefficient $R^{2}$ (0.93 and 0.90), and percent bias (PBIAS) ( $+ 13.36$ and $- 34.88 %$ ) values attained during the calibration (1985–1994) and validation periods (1995–2006), respectively, indicate that the SWAT can be used in this area to simulate the average annual soil erosion under different land-use scenarios. Two scenarios of land-use change, namely the conversion of farmland to forest and the conversion of grassland to farmland, were used to estimate runoff and sediment yield under typical rainfall conditions. In both land-use change scenarios, the value of sediment-yield change caused by land-use change increased with rain intensity, while the rate of sediment-yield change remained unchanged. Of the different soil types investigated, the greatest variation in sediment yield caused by land-use change occurred where loess is the underlying surface. Red soil shows the next greatest variation, followed by black and finally purple soil. The sensitivity of the four soils to the rate of sediment-yield variations is the opposite, with purple soil being the most sensitive, followed by red then black soils, and loess displaying the least sensitivity. The results of this study provide a reference that can assist in the evaluation of benefits of soil conservation projects in different regions and inform investment decisions.