Coupling the modified SCS-CN and RUSLE models to simulate hydrological effects of restoring vegetation in the Loess Plateau of China

摘要

Predicting event runoff and soil loss under different land covers isessential to quantitatively evaluate the hydrological responses ofvegetation restoration in the Loess Plateau of China. The Soil ConservationService curve number (SCS-CN) and Revised Universal Soil Loss Equation(RUSLE) models are widely used in this region to this end. This studyincorporated antecedent moisture condition (AMC) in runoff production andinitial abstraction of the SCS-CN model, and considered the direct effect ofrunoff on event soil loss by adopting a rainfall-runoff erosivity factor inthe RUSLE model. The modified SCS-CN and RUSLE models were coupled to linkrainfall-runoff-erosion modeling. The effects of AMC, slope gradient andinitial abstraction ratio on curve number of SCS-CN, as well as those ofvegetation cover on cover-management factor of RUSLE, were also considered.Three runoff plot groups covered by sparse young trees, native shrubs anddense tussock, respectively, were established in the Yangjuangou catchmentof Loess Plateau. Rainfall, runoff and soil loss were monitored during therainy season in 2008–2011 to test the applicability of the proposedapproach. The original SCS-CN model significantly underestimated the eventrunoff, especially for the rainfall events that have large 5-day antecedentprecipitation, whereas the modified SCS-CN model was accurate in predictingevent runoff with Nash-Sutcliffe model efficiency (EF) over 0.85. Theoriginal RUSLE model overestimated low values of measured soil loss andunderpredicted the high values with EF values only about 0.30. In contrast,the prediction accuracy of the modified RUSLE model improved with EF valuesbeing over 0.70. Our results indicated that the AMC should be explicitlyincorporated in runoff production, and direct consideration of runoff shouldbe included when predicting event soil loss. Coupling the modified SCS-CNand RUSLE models appeared to be appropriate for evaluating hydrologicaleffects of restoring vegetation in the Loess Plateau. The main advantages,limitations and future study scopes of the proposed models were alsodiscussed.