Multi-criteria decision making and fairness evaluation of water ecological carrying capacity for inter-regional green development.

Determining water ecological carrying capacity (WECC) is of great significance to ensure inter-regional green development. This study presents a comprehensive evaluation framework for WECC assessment in the Yangtze River Economic Zone (YREZ), China. Effects of water resources, socio-economic, and ecological elements on WECC can be evaluated based on multi-criteria decision analysis. Gini and unbalance coefficients are used for measuring the regional fairness between WECC and socio-economic development. Surface water production pressure (SWPP) and groundwater pollution risk (GPR) are further regarded as indicators for expressing water resources constraint on shale gas extraction in the YREZ. Results disclose that the average WECC level decreases from 0.439 in 2000 to 0.4007 in 2016, which is the opposite of the changing trend in the Beijing-Tianjin-Hebei Region. A high WECC level appears in Zhejiang (0.5126) with a good state, but that of Guizhou (0.3983), Anhui (0.3968), Hunan (0.3914), and Chongqing (0.3651) are at the alert state. The obstacle factors of WECC in the eastern YREZ mostly originate from socio-economic and water resource subsystems, while that in the middle and western YREZ mainly arise from water resources and ecological subsystems. Fairness analysis shows a well-matching characteristic between the overall WECC and socio-economic performances due to a majority of their Gini coefficients lower than 0.4, while a poor matching characteristic exists in terms of provincial differences owing to their varied unbalance coefficients, especially in Guizhou, Jiangsu, and Shanghai. Moreover, Chongqing with most of shale gas reserves is characterized by slight SWPP (1.0202) and GPR (0.0188), but the prospect of shale gas development in Sichuan is not optimistic due to its high SWPP (1.0846) and GPR (0.0647). Recycling of flowback and product waters can significantly lighten regional water resources pressure. This presented framework can be applied into many other Chinese cities (e.g., Beijing-Tianjin-Hebei Region) with slight modifications according to their actual situations for supporting water resource managers and government with decision making.