The N-shaped industrial water use environmental Kuznets curve and its formation mechanism: a case study from Shandong Province

The industrial water use environmental Kuznets curve (EKC) and its formation mechanism can not only indicate the relationship between industrial water use and economic development,but also provide important information for industrial water use management. The cubic model,quadratic model,and Locally Weighted Scatterplot Smoothing (LOWESS) were used to identify this relationship in Shandong Province. To quantitatively analyze the formation mechanism of the industrial water use EKC,the contributions to the change in industrial water use by the three drivers,including water use efficiency (WUE),industrial structure and economic scale,was calculated by the logarithmic mean divisia index (LMDI) method;while the long-term change characteristics of industrial WUE was analyze by the four-parameter logistic curve. Results indicate that the industrial water use in Shandong Province during 1980-2016 first increased,then declined,and finally increased again;further,there is an N-shaped EKC,in addition to the inverted U-shaped one. After the WUE is greatly improved and industrial water use continuously reduced,the WUE will gradually approach its limit. Thus,the rate of improvement of water use efficiency slows down and the water saving effect is greatly reduced. When the increase in water use caused by the expansion of the economic scale cannot be offset,the industrial water use will increase again instead of decline,and the shape of the curve changes from an inverted U-shaped to N-shaped. The existence of an N-shaped curve indicates that the industrial water use may increase again instead of an automatic continuous decline. To reduce industrial water use,it is necessary to make full use of the water-saving potential,continuously improve water use efficiency,and adapt the industrial structure to promote water saving.