Study on multi-objective water resources optimal allocation in water network areas based on water-energy-carbon synergistic governance

Study area Northern Jiangsu Study focus Water resources optimal allocation is essential for coordinating regional water-use conflicts and promoting sustainable development. However, existing models face challenges in representing complex hydrodynamic processes in plain river networks with strong human interventions, and the integration of carbon considerations into water allocation remains limited. This study develops a Water-Economic-Carbon-Spatial Multi-objective Optimization Model (WEC-SMOM). The framework integrates generalized river network hydrodynamic modeling with NSGA-III-based multi-objective optimization and a projection pursuit-based compromise solution selection method to coordinate water-supply reliability, economic benefits, and carbon emissions under complex flow conditions. New hydrological insights for the region Applied to Northern Jiangsu, the proposed framework quantifies trade-offs among economic benefits, water-supply reliability, and carbon emissions. Results reveal two independent pathways for reducing water shortages. Under unchanged infrastructure conditions, the regional water shortage rate decreased from 2022 to 2035 by 4.4, 0.3, and 0.2 %age points under the 95%, 75%, and 50% water-supply guarantee scenarios, respectively. Under identical demand-year and hydrological conditions, HRSC-II reduces water shortages by an additional 2.7–5.4 %age points during extremely dry years compared with the pre-project scenario, with reductions exceeding 6 %age points in some terminal cities. These findings distinguish the contributions of demand management and infrastructure development and provide insights for sustainable allocation in complex river network systems.