No abstract

Revegetation projects are beneficial measures used to control soil erosion, though they can adversely affect the water yield of semiarid watersheds. In this study, Dali River basin that is a semiarid basin with intensive ecological restoration strategies on the Loess Plateau of China was selected as an extreme condition to examine how revegetation projects affect watershed runoff. In the study watershed, the vegetation indicator Normalized Difference Vegetation Index (NDVI) and Soil Adjusted Total Vegetation Index (SATVI) increased by 6.9% and 189.1% after 2000, respectively.Human activities contributed most to vegetation increase (77.1% for NDVI and 98.6% for SATVI). We quantified the response of runoff change to revegetation within a physically based modelling framework that incorporated the effects of check-dam construction and was constrained by the observed runoff data. The results showed that revegetation explained 29.2% of the runoff decrease in the impact period 2 (2000-2010), but its contribution was lower than that of check-dam construction (75.2%). Compared with climatic factors, implementation of the two ecological restoration projects was the dominant driver of runoff reduction after 2000. This study demonstrates the importance of attribution analysis in an integrated modelling framework with revegetation and other ecological restoration projects and constrained by the observed runoff data.