Attribution of Hydrologic-Cycle Changes to Climate Change and Human Activities in the Shaying River Basin, China

The Shaying River Basin, the largest tributary basin of the Huaihe River in eastern China, is a representative north–south transitional basin with strong mountain–plain contrasts and intensive human disturbance. This study quantified hydrologic-cycle changes and attributed them to climate change and human activities using the Simulation Water-cycle and Allocation Model (SWAM). Hydrologic processes were simulated for a baseline period (1971–1980) and a changed-environment period (2001–2010). Four scenarios were designed to isolate the effects of climate change, land-use change, and water-resource development. The results show clear spatial differences in hydrologic response. At the basin scale, human activities and climate change contributed 59% and 41%, respectively, to hydrologic-cycle changes. In the plain area, human activities were dominant, contributing 67%, whereas in the mountainous area, climate change was dominant, contributing 61%. Water-resource development reduced surface-water, soil-water, and groundwater storage, especially in the plain area. These findings highlight the need for differentiated water-management strategies in transitional basins and provide a representative case for understanding climate–human impacts on hydrologic-cycle changes.