Quantitative contribution of climate change and human activities to runoff changes in the Bahe River watershed of the Qinling Mountains, China

Climate change and human activities are the two major driving factors that affect the hydrological cycle. This study analysed the streamflow changes during 1958-2015 and related them to climate and land surface alterations in the Bahe River watershed of the Qinling Mountains by using the Budyko framework. The Pettit test method was used to investigate abrupt changes, and the Mann-Kendall test method was employed to assess monotonic trends. The results showed that annual runoff exhibited a significant declining trend, with a change point found in 1989. Annual precipitation and potential evapotranspiration showed decreasing and increasing trends, respectively, but neither were significant. The hydrological responses were more sensitive to land surface alterations than climate variability. The contributions of climate change and land surface alterations to changes in runoff were 25.50 and 74.50%, respectively. The watershed characteristics parameter played a primary role, which indicates that runoff variability is most sensitive to land surface alterations due to vegetation change and land use and land cover change. This study could provide a scientific basis for how to effectively and efficiently mitigate changes in water resources and guide measures to be implemented in the region under future climate change.