Dynamic assessment and influencing factors analysis of water environmental carrying capacity in the Yangtze River Economic Belt, China

Improving water environmental carrying capacity (WECC) is pivotal to support water sustainability and continued economic development. The improvement pathways of WECC based on both subsystem coupling and driving factors have not yet been identified. Therefore, taking the Yangtze River Economic Belt (YREB) as a case study, this paper firstly constructed a set of scientific comprehensive evaluation index system of WECC based on the coupling system of water resources-water environment-society-economy. Secondly, the improved catastrophe progression method was properly introduced to dynamically evaluate the level of provincial WECC from 2010 to 2018. Finally, the coupling coordination degree (CCD) and obstacle factor diagnosis model were creatively combined to identify the main influencing factors of WECC. The main findings were as follows: (1) The WECC of the YREB was generally low at the provincial and subsystem levels without any obvious upward trend. In comparison, the WECC was higher in Shanghai City, Zhejiang Province and the lower reaches of the YREB. (2) The CCD among the four subsystems was generally low in the YREB. Meanwhile, there was a significant positive correlation between the CCD and WECC in each provincial area, and thus the low CCD was a vital reason for the low WECC in the YREB. (3) Overall, the economic subsystem had the highest restriction on WECC improvement in the YREB, while that of the water resources subsystem had the least. Seen from the mean, the top five obstacle factors of WECC were proportion of ecological environment water consumption, urbanization rate, per capita GDP, proportion of tertiary industry and water consumption per unit of GDP respectively. Furthermore, the rankings of main obstacle factors showed a certain time fluctuation. In general, it could be found out that the CCD of subsystems and main obstacle factors should be focused on simultaneously when improving regional WECC. Additionally, this study has provided a new analytical framework for identifying the pathways of improving WECC, which is also applicable to find the improvement pathways for stability and safety of other complex systems.