Quantifying future water resource vulnerability in a high-mountain third pole river basin under climate change.

Understanding the water resource vulnerability (WRV) in global mountain regions under climate change is crucial for water resources management and socio-economic development. However, the WRV in the high-mountain Third Pole region (with quite a few transboundary river basins) remains largely unclear. Here, we have applied a comprehensive assessment framework of WRV to a Third Pole high-mountain river basin (Nujiang-Salween River, NSR) and its dependent downstream. The framework consisted of sensitivity, exposure, adaptability, hazard, and water stress indices, considering climate change, socio-economics, government effectiveness, natural disasters, and water supply capacity of the target river basin. Our results indicate that the downstream area (with intensive human activities) often exhibited significantly higher WRV than the mountain region; while the WRV shows an M-shaped change with increasing elevation, with the highest vulnerability occurring in a relatively low elevation range (e.g., 500-1500 m for the NSR basin). In the near future, we find that the spatial pattern of WRV in the basin is alternately influenced by adaptation, water scarcity, and exposure; whereas climate change serves as the main driver affecting the WRV in the far future. These findings enhance our understanding of the WRV in high-mountain transboundary basins of the Third Pole under global change.