Simulation and Dynamic Assessment of Urban Water Metabolism Using an ABM–SD-Coupled Model: A Case Study of Beijing

Water-scarce megacities undergoing rapid urbanization and climate change often face imbalances in urban water metabolism, characterized by the coexistence of socioeconomic growth and increasing pressure on water environmental carrying capacity. To address the limitations of existing studies in capturing the dynamic evolution of urban water systems, this study develops an urban water metabolism simulation model based on an agent-based modeling and system dynamics (ABM–SD)-coupled framework. The model represents the system evolution mechanism of “micro-level decision making–macro-level feedback” by incorporating the behavioral interactions of multiple agents, including the government, residents, and enterprises. On the basis of model simulation, the coupling coordination degree (D) and the Nemerow index (PI) are introduced to construct a two-dimensional D–PI state space, thereby enabling the dynamic assessment of the coordination and sustainable development status of the urban water metabolism system. Taking Beijing as a case study, the simulation results show that the coordination degree between socioeconomic development and the water environment continues to improve, while pressure on the water environmental carrying capacity continues to accumulate. Overall, the system exhibits a non-synchronous evolutionary pattern characterized by improved coordination alongside increasing carrying-capacity risks.