A Coupled Model of System Dynamics and Environmental Models for the Development Process Deduction of the Yangtze River Basin: Model Construction Method

The Yangtze River Basin, the largest river basin in China, faces complex challenges in population, economy and water issues. This study builds a Systemic Deduction Model of the Development of Yangtze River Basin (SDMY), which is based on system dynamics coupled with the water environmental model. It generalizes the Yangtze River Basin into five subsystems at the province level as well as two subsystems at the river basin level, quantifying the interaction and feedback relationships within and among each subsystem through functions. SDMY has passed the feasibility verification and the sensitivity analysis. The application results from 2000 to 2100 of SDMY show the positive development trend of gross domestic product (GDP), grain production, energy consumption, and forest coverage, as well as the significant risk of population decline. The water pollutants chemical oxygen demand (COD) and total phosphorus (TP), the water security level, and the river longitudinal connectivity of the Yangtze River Basin show reasonable and meaningful development trends, as the results indicate. This paper proves that SDMY could be a quantitative simulation tool for analyzing the long-term mutual feedback and evolution of the human–water relationship and society–economy–environment system in a large river basin.