Navigating Climate Adaptation Boundaries for the World's Largest Inter‐Basin Water Transfer Projects

Abstract As global climate change and human impacts intensify, their effects on streamflow are becoming critical for water security. This study investigates the hydrological impacts of future scenarios on the Yangtze, Yellow, Huaihe, and Haihe basins using a 5‐km daily resolution Spatial Processes in Hydrology model. We integrate water use and water transfer processes to establish a climate‐human‐hydrology framework and apply a threshold‐based climate‐responsive water transfer strategy to improve Directional Impact of Outflow (DIO) of each water transfer route. Our findings suggest that increased glacier melt and precipitation drive a net increase in streamflow and prolonged autumn flooding across all basins. Decomposition analysis reveals distinct regional vulnerabilities in Huaihe River Basin with extreme nonlinearity, where opposing climate and human interaction effects nearly cancel out, creating profound uncertainty. The Central Route, historically the most efficient among three transfer routes, shows a significant decline in DIO under future climate (28%–31% reduction), as wetter conditions reduce transfer demand. The Western and Eastern Routes remain stable and less sensitive to climate change. To address these shifting patterns, we apply a threshold‐based climate‐responsive strategy. Results demonstrate that optimizing reallocation yields up to a 7% improvement in DIO for the Central Route. This study highlights that resilient water management must move beyond static infrastructure, adopting adaptive strategies that account for non‐linear hydrological responses and shifting seasonal availability to buffer against climate extremes.