Dynamic successive assessment of water environment carrying capacity based on a system dynamics model and an improved variable fuzzy pattern recognition method

Water environment carrying capacity (WECC) is both a natural attribute of the water environment and a social attribute that governs regional sustainable development. Jiangsu Province, characterized by a large population and rapid economic growth, faces increasing challenges such as imbalance between water supply and demand and deteriorating water quality. Therefore, assessing WECC in this region is of great importance. Based on an analysis of water resource utilization and water quality conditions, a set of indicators for evaluating WECC was established using the Driving-Pressure-State-Impact-Response (DPSIR) framework. Grey correlation theory was applied to screen these indicators. To account for the different interpretations of index weights with respect to evaluation targets and objects, the variable fuzzy recognition method (VFPR) for water quality evaluation was enhanced by integrating the Analytic Hierarchy Process (AHP) and entropy weight method (EWM). This integration ensures that index weights reflect both objective data and expert judgment, thereby improving their rationality. The results indicate that from 2003 to 2021, WECC in Jiangsu Province declined due to rapid economic development and population growth, but gradually stabilized as economic advancement continued, highlighting a reciprocal relationship between WECC and socio-economic development. A dynamic WECC model for Jiangsu Province was developed using Vensim software and applied to scenarios designed to enhance WECC. The predicted development trends under different scenarios allowed the identification of an optimal scenario. A comprehensive evaluation of six scenarios between 2022 and 2030 suggests that maintaining the current high-speed development model would lead to a continued decline in WECC. In contrast, effective water-saving measures and strengthened sewage treatment can greatly improve water resource carrying capacity, maintaining it at a “positive carrying” level while supporting steady socio-economic growth. These findings provide valuable guidance for Jiangsu Province in enhancing its WECC and aligning socio-economic development with environmental sustainability in its top-level planning.