Growing Imbalance Between Supply and Demand for Flood Regulation Service in the Asian Water Tower and Its Downstream Region

Quantifying the supply-demand dynamics of the flood regulation service (FRS) is crucial for effective flood risk management. However, current methods cannot adequately capture high-altitude hydrological processes, leading to flawed assessments of climate change impacts on FRS in such regions. Here, we improve the methodology for estimating the supply-demand dynamics of FRS and quantify this relationship from 1990 to 2020 within the Asian Water Tower (AWT) and its downstream region. By integrating climate model data with bias correction, we estimate the supply-demand ratio (SDR) of FRS during 2020–2050 on multiple scales. Our findings show that the FRS imbalance in the AWT and its downstream region will persist and intensify. Specifically, more than 44% of the region experienced a significant decline in the SDR during 1990–2020. It is projected that 65.8 ± 2.1% of the region will experience a significant decline in the SDR during 2020–2050 (SSP5-8.5 scenario). Climate and socioeconomic changes have jointly exacerbated this imbalance, with relative contributions of 58.4% and 41.6%, respectively, and such an imbalance further amplifies flood risk. We propose addressing the FRS imbalance from both the supply and demand sides and strengthening cooperation among upstream and downstream regions and internationally within the Indus and Ganges-Brahmaputra basins.