Spatial patterns of industrial water efficiency and influencing factors -based on dynamic two-stage DDF recycling model and geographically weighted regression model

Facing water scarcity and water pollution, improving recycling water efficiency has become a crucial task, especially in urban areas. This research proposes a dynamic two-stage recycling model within the directional distance function (DDF) which takes reused water in the wastewater treatment (WT) as a recycled product for clean water use (WU) stage's input in the next period. To comprehensively evaluate the efficiency of industrial recycling water from the perspective of quality and quantity, greywater footprint and wastewater discharge are treated as unexpected outputs. Moran' I and Spatial Error Model (SEM) are applied to analyzing the spatial correlation and screening out the key influencing factors of industrial recycling water efficiency in China, furthermore, geographically weighted regression (GWR) model being built to measure spatial heterogeneity of the key influencing factors. The results reveal that: The overall efficiency of industrial recycling water efficiency in China is 0.75, which has not reached the effective utilization status. The integrated system is efficient if and only if both subsystems are efficient, especially wastewater treatment subsystems. China's industrial recycling water efficiency does not show obvious spatial autocorrelation, and its local differences have experienced the transformation from spatial agglomeration dominated by wastewater treatment subsystems to spatial hetero-geneity dominated by clean water use subsystems. Besides, water resource endowment and water structure are conducive to improving the efficiency, while industrial water intensity inhibits its improvement. There still existed spatial heterogeneity of influencing factors where regional industrial structure and industrial water in-tensity effect acted as a stimulus to industrial recycling water efficiency in the central and western regions, in contrast, water resources endowment and water structure mainly boosting in the eastern region, and environ-mental negative effect mainly inhibiting in the southeast coast and central region of clean water use efficiency. Some policy implications from provincial and national perspectives are suggested.