Efficiency and driving force assessment of an integrated urban water use and wastewater treatment system: Evidence from spatial panel data of the urban agglomeration on the middle reaches of the Yangtze River.

With the rapid development of urban agglomerations, urban water use and wastewater environments have gradually constrained sustainable development and caused increasing concern. In this paper, we selected the urban agglomeration on the middle reaches of the Yangtze River (UAMRYZ) as a typical area. We proposed an integrated urban water use and wastewater treatment (UWUWT) system and its urban water use (UWU) subsystem and urban wastewater treatment (UWT) subsystem. Moreover, an integrated two-stage slacks-based measure (SBM) data envelopment analysis (DEA) model was used to evaluate the efficiency of the UWUWT system and its subsystem during 2010 to 2017. Additionally, the multiscale geographically weighted regression (MGWR) model was adopted to analyze the influence mechanism of each factor on the defined system. The results indicated that the tendency of UWU efficiency and UWUWT efficiency were similar and mainly showed the same trend with an 'N' shape in a time-dependent manner for the UAMRYZ and provinces, respectively. Furthermore, the UWU efficiency and UWUWT efficiency of each city showed strong spatiotemporal heterogeneity. The UWT efficiency of the UAMRYZ and its representative cities was stable in the region and always had a higher value. With continuous economic development and increased interregional foreign trade, the UWU subsystem efficiency and the UWUWT system efficiency had a significant increase for cities along the entire river in the Yangtze Basin. The regional differences of the overall UWU efficiency, UWT efficiency and UWUWT efficiency gradually decreased and the efficiency has gradually improved from 2010 to 2017. Attribution analysis showed that the secondary industry was the main constraining factor, while the water resource was the most acceleration factor for the UWUWT system in most areas and the UWT subsystem for all cities. Our study evaluated the specific insufficiencies of the defined system and supported regulatory policies.