Spatiotemporal Contributions of Advected and Recycled Moisture to Water Resource Variability in China

Water security in China is challenged by pronounced spatial and temporal heterogeneity in water resources, driven by distinct moisture sources: advected (externally transported) and recycled (locally generated) moisture. However, the quantitative impacts of different moisture sources on hydrological variability remain unexplored. This study quantified their contributions to precipitation (P) and water availability (WA) across China and its nine major river basins from 2000 to 2022 using atmospheric moisture tracking. We propose a novel decomposition framework to partition the variability of total P and WA into independent contributions from each moisture source and their synergistic interactions. We find that synergistic effects between the two sources amplify national-scale spatial disparities but mitigate intra-basin heterogeneity in five of the nine major basins. At the national scale, advected moisture peaks earlier in the year than recycled moisture. However, a distinct north-south contrast emerges: southern regions depend more on advected moisture, while northern regions depend primarily on recycled moisture. Unsynchronized peaks between advected and recycled moisture in southern basins buffer seasonal extremes, whereas synchronized peaks in northern basins intensify intra-annual variability. These findings underscore the need for region-specific water management: climate-informed strategies for advected moisture-dependent regions and land-atmosphere feedback-aware approaches for recycled moisture-reliant areas. This study provides a framework for addressing hydrological imbalances under changing climate and land-use patterns.