Moisture Transport and Recycling Shape Wetting and Drying Across China: Implications for Water Sustainability

Global warming is reshaping the global dry–wet pattern, yet its future trajectory remains uncertain, with important implications for sustainable water resources. China, influenced by both the monsoon system and the mid-latitude westerlies, requires an integrated assessment linking net water balance (precipitation minus evaporation, PME) to moisture transport. Here we use precipitation, evaporation, and air temperature records for 1981–2023, together with Lagrangian moisture tracking and precipitation recycling diagnostics, to quantify changes in PME across China and to identify the underlying mechanisms. We further assess future evolution under different warming levels (1.5 °C, 2 °C, and 3–4 °C) for 2024–2099 using a CMIP6 multi-model ensemble. China experienced a pronounced warming during the historical period, while precipitation declined overall and evaporation remained nearly stable. As a result, reduced moisture supply strengthened drought sensitivity. Spatially, warming-driven drying is concentrated in the eastern and southern monsoon regions. In contrast, the inland arid and semi-arid Northwest and parts of high-elevation transition zones show a relative shift toward warmer and wetter conditions. Moisture transport diagnostics indicate that China’s moisture supply is jointly sustained by the mid- to high-latitude westerlies and low-latitude oceanic monsoon pathways. These pathways form a continuous transition from the Northwest to the Southeast. Land–atmosphere recycling is stronger in the Southeast, whereas the Northwest depends more on imported moisture, with plateau topography further reshaping the main transport corridors. In the future, PME continues to decline under 1.5 °C warming. Under 2 °C warming, PME enters a transitional state with patchy regional patterns. Under 3–4 °C warming, PME shifts to an overall increase, but uncertainty becomes larger. These results identify a critical turning window at around 2–3 °C warming for China’s PME response, providing a physical basis for sustainable water-resource management and adaptation planning.