Comprehensive assessment of the water environment carrying capacity based on the spatial system dynamics model, a case study of Yongding River Basin in North China

The Chinese water environment system is severely degraded by intensive anthropogenic activities. To relieve these problems, the national government has proposed to establish a comprehensive evaluation system of water environment carrying capacity (WECC). However, few studies provide a comprehensive depiction of the spatiotemporal heterogeneity of WECC within a basin/region owing to the limitations of interdisciplinary research methods. By integrating the system dynamics model, cellular automaton model, and gridded geographic information system technology, we developed a spatial system dynamics model to explore the spatiotemporal pattern of the WECC of Yongding River Basin in North China. The spatial system dynamics model works well and the simulation accuracy was close to 85%. Our results showed that inadequate water resources and water quality induced the overloaded WECC in Yongding River Basin, which was unevenly distributed within the river basin. From 2017 to 2035, Zhangjiakou often suffered an overload of WECC throughout the year due to quantity-related water shortages. However, in Beijing's mountainous area, the WECC status of control units 1 and 4 was in good status owing to sufficient water quantities. Considering the overload of the WECC and its feedback relationship with anthropogenic activities, effective and feasible management measures, such as reducing agricultural irrigation water use and domestic pollution, improving the rate of sewage collection and treatment, or industrial restructuring should be prioritized in this arid river basin. Our study improved methodologies in WECC modeling for river basins, helped overcome difficulties in revealing the spatiotemporal dynamic patterns of WECC, proposed a calculation method of WECC in terms of population and GDP, and verified that the threshold of WECC was not static, which provides information for finding a balance between economic development and water safety, especially in regions with water scarcity.