Attribution of Future Water Stress in a Two-Way Coupled Socioeconomic–Hydrological Framework

Abstract

Water scarcity arises from the complex interplay between socioeconomic water demand and hydrological water availability, yet most global assessments represent these components separately or through one-way coupling. This limits their ability to capture dynamic feedbacks between socioeconomic and hydrological processes. In this study, we developed a two-way coupled socioeconomic–hydrological framework linking the Global Change Analysis Model and the Integrated Land Simulator. The framework dynamically exchanges land-use and hydrological water-availability information between the two models, enabling internally consistent representation of water demand and hydrological water availability through bidirectional feedbacks. We performed century-scale simulations from 2020 to 2100 under SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5, with ILS at 0.5° resolution and Global Change Analysis Model operating over 32 geopolitical regions. Benchmark evaluation showed that the coupled configuration maintained statistically consistent performance in reproducing global water withdrawals and agricultural prices while modestly improving river-discharge consistency. Using this framework, we decomposed future changes in water stress into socioeconomic and hydrological contributions. Across all four Shared Socioeconomic Pathways and Representative Concentration Pathways scenarios, roughly 80% of global geopolitical sub-basin area exhibits increases in water stress. Areas where hydrological change is the dominant contribution account for about 20% under SSP1–2.6 and SSP2–4.5, rising to roughly 30% under SSP3–7.0 and SSP5–8.5. Regionally, Africa's future water-stress intensification remains largely socioeconomic because of sustained demand growth, whereas Central Asia increasingly exhibits hydrologically driven water stress as water availability declines. These results demonstrate that future water scarcity cannot be explained by climate or socioeconomic demand alone, but is shaped by coupled socioeconomic–hydrological feedbacks. The proposed framework provides a foundation for dynamic, region-specific water resources management under future Shared Socioeconomic Pathways and Representative Concentration Pathways scenarios.