Co-evolution and Adaptive Management of the Water-Sediment- Ecology-Socioeconomic Nexus under Climate-Socioeconomic Change

Understanding the coupled interactions among water resources, sediment processes, ecological restoration, and socio-economic development is critical for sustainable river basin management under changing environments, particularly in arid and semi-arid regions. The Ningxia reach of the Yellow River Basin represents a strongly human-impacted system in arid/semi-arid area, where water scarcity, intensive regulation, and ecological vulnerability coexist. In this study, we develop an integrated water-sediment-ecology-socioeconomic (WSES) nexus framework based on System Dynamics to investigate long-term co-evolutionary processes and policy trade-offs in this region. The model explicitly couples hydrological dynamics, sediment transport, ecological restoration measures, and socio-economic development, and is calibrated using long-term observational and statistical data. By combining afforestation and grassland restoration scenarios with SSPs-RCPs climate-socioeconomic pathways, we simulate system responses from 2010 to 2050. Results reveal pronounced nonlinear relationships and trade-offs between ecological benefits and water availability, identify threshold behaviors in water-sediment regulation, and demonstrate that high-emission pathways substantially amplify hydrological and environmental risks. Moderate ecological restoration under low-emission development pathways emerges as a more robust and adaptive strategy for balancing water security, sediment control, and economic growth. This WSES-oriented modeling framework moves nexus research beyond static coupling toward dynamic risk-informed decision support, offering a transferable approach for managing complex human-natural river systems under compounded climate and socio-economic uncertainty.