Spatial disparities and water resource green efficiency improvement potential in the four-city area in middle China

To address the dual constraints of resource shortages and environmental degradation, the water resource green efficiency (WRGE) concept, which takes into account socioeconomic and green development, has been adopted as a basis for implementation of cleaner production strategies and sustainable economic development. In the present study, the meta-frontier undesirable super-efficiency slack-based measure (Meta-US-SBM) model, which allows for technological heterogeneity across regions, was employed to estimate WRGE in 38 regions in the four-city area in middle China in 2010–2019, and the technology gaps of different regions and categories were discussed. Subsequently, the improvement potential of WRGE (WEIP) in different regions was mapped using the slacks of water resource ecological footprint input and GDP output obtained using the Meta-US-SBM model. According to the results, the regions with the highest average WRGE under group-frontier and meta-frontier groups were Huangshi and Qianjiang, respectively, whereas the category with the highest average WRGE was EOU (regions where economic benefits outmatch urbanization benefits). Surprisingly, the WRGE technology gaps among different regions and categories showed considerable differences. We observed a negative correlation between WEIP and WRGE. Moreover, there were obvious differences in water resource ecological footprint improvement potential among different regions and categories.