The DPSIRM - Grey cloud clustering method for evaluating the water environment carrying capacity of Yangtze River economic Belt

Water Environment Carrying Capacity (WECC) is a complex system affected by society, economy, population and other factors. In this study, "Driving force- Pressure -State - Influence - Response -Management" (DPSIRM) method is introduced to analyze regional WECC, that is, WECC system is classified into six subsystems to illustrate its internal mechanism, establishing a systematic evaluation index system affecting WECC. The Fuzzy Analytic Hierarchy Process (FAHP)-Grey cloud clustering method is developed for making comprehensive WECC evaluation. Three major regions composed of 11 provinces in the Yangtze River Economic Belt (YREB) of China are selected as the study case. With regard to subsystem weights, the results show that pressure and state subsystems occupy a leading position on the whole system. For indicator weights, there are significant differences among them, and the top 5 indicators in importance are respectively: annual average total phosphorus (TP) concentration, soil erosion control rate, sediment delivery modules, wastewater effluent amount of industrial output value per 10,000 Yuan, and population density. In addition, through analyzing synthetic evaluation results, it can be found that WECC levels of different provinces present obvious spatial heterogeneity on each subsystem and overall system along the YREB, that is, they decrease along the Yangtze River from west to east except for minor deviations. Meanwhile, comprehensive scores of each regional WECC show an overall increasing trend from year 2014 to 2019, displaying significant temporal variations. Through making sensitivity analysis for WECC index system, it can be concluded that the most sensitive indicators of each subsystem are Population density, Wastewater effluent amount of industrial output value per 10,000 Yuan, Annual average TP concentration, Sediment delivery modules, Soil erosion control rate, Green coverage rate of built-up areas, respectively, which also turned out to be the top six sensitivity indicators among the whole index system. Finally, the demonstration conducted proves that the introduced DPSIRM - Grey cloud clustering method is applicable and effective to evaluate WECC at regional level.