Water resources system vulnerability in high mountain areas under climate change

Influencing socio-economic development and ecological environment, water resources system vulnerability (WRSV) is becoming increasingly prevalent in high mountain areas, which are strongly affected by climate change. In this study, the Upper Yangtze River (UYZ) located in hinterland of the Tibetan Plateau was selected for assessing spatiotemporal variations in WRSV, predicting future WRSV and identifying the main influencing factors of WRSV. The spatiotemporal variations in WRSV were estimated based on a framework including sensitivity, exposure, hazard and adaptability, which considered impact of both natural and human activities on WRSV. Moreover, the main influencing factors of WRSV and its future evolution were obtained based on SPHY (Spatial Processes in Hydrology) model, GCMs (General Circulation Models) and attribution analysis. The average WRSV of the UYZ corresponded to medium-low grades during 2001-2019. Overall, the value and increasing trend of WRSV in downstream areas were higher than that of upstream areas. Under various scenarios (SSP 1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) with global warming of 1.5 degrees C and 2 degrees C, the average WRSV would continue to be of medium-low grade. However, the average WRSV of the basin and the area ratio for medium vulnerability and medium-high vulnerability would increase. As the main influencing factor, the hazard level contributed to more than 93% of the change in WRSV during both the historical and future periods. The results indicated that climate change may increase the WRSV of the UYZ and suitable countermeasures would be required to better cope with the impact of climate change on the water resources system. These findings provide a scientific basis for designing adaptive strategies to mitigate the adverse effects of climate change and achieve social and economic sustainable development.