Qualitative and quantitative analysis of the relationship between water pollution and economic growth: a case study in Nansi Lake catchment, China

Investigation of water pollution–economic growth nexus is an important component for the sustainable development of eco-environment and socio-economy. This study combined the improved Grey relational degree (GRD) model with the environmental Kuznets curve (EKC) to quantitatively and qualitatively investigate the relationships between water pollution and economic growth in Nansi Lake catchment (Jining, Zaozhuang, and Heze) under the context of the Five-Year Plan in Shandong. Results showed that the relational degree of industrial wastewater and economic growth was Heze (0.652) > Zaozhuang (0.581) > Jining (0.538), and of domestic wastewater and economic growth was Jining (0.722) > Heze (0.721) > Zaozhuang (0.650). Meanwhile, the EKC of industrial wastewater rose and then declined, whereas that of domestic wastewater increased upwards. Overall, coordinated development had been gradually obtained between industrial wastewater emissions and economic growth. And, uncoordinated development between domestic wastewater emissions and economic growth still existed, indeed, in recent years it had intensified. Further, domestic wastewater emissions continue to rise, to the point where they now constitute one of the main sources of water pollution in Nansi Lake catchment. Results of this study indicated that combining the improved GRD model with the EKC provides a new approach to comprehensive investigation of the water pollution–economic growth nexus from a qualitative and quantitative perspective.