Quantifying the altitudinal response of water yield capacity to climate change in an alpine basin on the Tibetan Plateau through integrating the WRF-Hydro and Budyko framework

Alpine areas play a substantial role in supplying the world’s water resources. The hydrological cycle in these areas has been experiencing notable alterations owing to climate change. However, the present comprehension of how water yield capacity (WYC) responds to climate change at varying elevations within alpine basins is impeded due to the complex terrain and simplified representation of coupled water-energy processes in traditional hydrological models. Through integrating the Weather Research and Forecasting hydrological modeling system (WRF-Hydro) and Budyko framework, this study quantitatively assessed the influence of climate change on WYC across different elevations in a Tibetan Plateau alpine basin, named Xiying River Basin (XRB). The results indicated the WRF-Hydro adeptly reproduced the streamflow and evapotranspiration (ET) within the XRB. The combination of the WRF-Hydro model allows the Budyko framework, traditionally limited to the watershed scale, to be applicable at the grid scale. We found that the XRB underwent substantial climate change from 1980 to 2015, and there existed an abrupt change in 1997. Climate change caused the WYC reduced by −17.06% during the post-1997 period (1998–2015), compared to the pre-1997 period (1980–1997). Additionally, all elevation bands displayed the WYC reductions, ranging from −3.69% to −24.31%, with diminishing magnitude at higher elevations. This WYC reduction is primarily attributed to an increase of 11.38% in ET. Although ET and precipitation increased with elevation, the former consistently exceeded the latter, resulting in decreasing water deficits and an altitudinal gradient of the WYC reduction. Besides the increasing vapor pressure deficit and decreasing albedo, our findings emphasized the significance of precipitation event timing in influencing WYC. The longer time intervals between precipitation events in the XRB led to more soil moisture loss through ET. These findings shed valuable implications for policymakers, offering guidance for the formulation of sustainable policies for water resource management and ecological conservation.