Spatio-temporal heterogeneities in hydrologic dynamics across the Asian Water Tower

This study presents a multi-decadal (1979–2018) analysis of hydrologic changes across the entire Asian Water Tower (AWT) region, using high-resolution hydrological-hydrodynamic modeling. We find significant spatiotemporal heterogeneity in hydrological trends across the AWT basins, characterized by diverse changes in river discharge, water storage, flood regimes, and terrestrial water storage (TWS) dynamics. Western basins such as the Amu Darya and Tarim show increasing flood risks (up to ∼60 % increase in flood occurrence) and significant snow water equivalent (SWE) contributions to TWS (up to ∼41 %), while central basins are transitioning to regions of increasing water scarcity with strong subsurface storage contribution evident in the Ganges (up to ∼79 %). The dominance of subsurface storage reaches its peak in the eastern basins, where the Yangtze and Yellow River exhibit the highest proportions (∼78 % and ∼83 % respectively), with the Yangtze further distinguished by a notable river storage contribution (∼21 %). In contrast, southeastern basins including the Mekong, Irrawaddy, and Salween present complex, temporally varying patterns that defy simple categorization. These findings highlight the complex interplay of surface and subsurface processes in the AWT, underscoring the need for basin-specific approaches in water resource management and climate change adaptation strategies.