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

G Y Gao,B J Fu,Y H Lü,J Zhou,S Wang,Y Liu

doi:10.5194/hess-16-2347-2012

Abstract

Abstract. Predicting event runoff and soil loss under different land covers is essential to quantitatively evaluate the hydrological responses of vegetation restoration in the Loess Plateau of China. The Soil Conservation Service curve number (SCS-CN) and Revised Universal Soil Loss Equation (RUSLE) models are widely used in this region to this end. This study incorporated antecedent moisture condition (AMC) in runoff production and initial abstraction of the SCS-CN model, and considered the direct effect of runoff on event soil loss by adopting a rainfall-runoff erosivity factor in the RUSLE model. The modified SCS-CN and RUSLE models were coupled to link rainfall-runoff-erosion modeling. The effects of AMC, slope gradient and initial abstraction ratio on curve number of SCS-CN, as well as those of vegetation cover on cover-management factor of RUSLE, were also considered. Three runoff plot groups covered by sparse young trees, native shrubs and dense tussock, respectively, were established in the Yangjuangou catchment of Loess Plateau. Rainfall, runoff and soil loss were monitored during the rainy season in 2008–2011 to test the applicability of the proposed approach. The original SCS-CN model significantly underestimated the event runoff, especially for the rainfall events that have large 5-day antecedent precipitation, whereas the modified SCS-CN model was accurate in predicting event runoff with Nash-Sutcliffe model efficiency (EF) over 0.85. The original RUSLE model overestimated low values of measured soil loss and underpredicted the high values with EF values only about 0.30. In contrast, the prediction accuracy of the modified RUSLE model improved with EF values being over 0.70. Our results indicated that the AMC should be explicitly incorporated in runoff production, and direct consideration of runoff should be included when predicting event soil loss. Coupling the modified SCS-CN and RUSLE models appeared to be appropriate for evaluating hydrological effects of restoring vegetation in the Loess Plateau. The main advantages, limitations and future study scopes of the proposed models were also discussed.

Highlights

Flash flood and soil erosion affect adversely the natural and human-management ecosystems
It substantially incorporates antecedent moisture condition (AMC) in runoff production and directly considers runoff in soil loss to overcome the major disadvantage of the traditional Soil Conservation Service curve number (SCS-CN) and Revised Universal Soil Loss Equation (RUSLE) models
In the modified RUSLE model, direct effect of runoff on event soil loss was considered by adopting a rainfall-runoff erosivity index (QREI30) to replace the traditional rainfall erosivity factor (EI30) (Eq 14)

Summary

Introduction

Flash flood and soil erosion affect adversely the natural and human-management ecosystems. In arid and semi-arid regions, water shortage is the key limiting factor (Wang et al, 2012). Changes in anthropogenic (e.g. land use) and natural (e.g. climate change) forcings will further affect hydrological cycles and water availability at all scales in these regions (Wang et al, 2012; Feng et al, 2012). Modeling of event- based rainfall-runoff and soil erosion processes under different land use conditions has significant importance, and has fundamental impact on hydrological practices. Gao et al.: Coupling the modified SCS-CN and RUSLE models

Objectives

Discussion

Conclusion