| Water resources are one of the key factors for the ecological civilization construction and green development of the Yangtze River Economic Belt.Cities along the Yangtze River Economic Belt are relatively rich in water resources,but there are problems such as waste of water resources,low utilization efficiency,and supply-demand contradictions.In addition,the proposal and implementation of the "Three Red Lines" for the strictest water resource management,water-saving society,and rational and efficient utilization of resources make it necessary to study the green efficiency of water resources and the potential for water conservation and emission reduction in cities along the Yangtze River Economic Belt.This paper takes 45 cities along the Yangtze River Economic Belt as the research object.Based on the use of the SE-SBM model(Super-Efficiency Slacks-Based Model)to calculate the green efficiency of urban water resources.Combined with the decomposition of Theil index,the root causes of regional differences in green efficiency of water resources are explored,and the ML index method(Malmquist-Luenberger)is used to explore the internal causes of changes in green efficiency of water resources;Furthermore,the difference between the actual value and the optimal value of water resources input and water pollutant output is used to calculate the water-saving and emission reduction potential of 45 cities along the Yangtze River Economic Belt.And summarize the following conclusions:(1)From 2010 to 2019,among the 45 cities along the Yangtze River Economic Belt,77.8%of the cities had inefficient water resource green efficiency,resulting in a wide range of redundant resource inputs,insufficient output of social development indicators,and excessive output of sewage and industrial wastewater.From a regional perspective,the spatial distribution of green efficiency of water resources in the three major regions presents as follows:downstream of the Yangtze River Economic Belt>upstream>middle reaches,with efficiency values not reaching effective values and there is a lot of room for optimization.There are significant regional differences in the green efficiency of water resources in cities along the Yangtze River Economic Belt,mainly caused by the efficiency gap among cities in the upstream,middle,and downstream regions.(2)From 2010 to 2019,the green efficiency of water resources in nine cities,including Zhaotong,Lijiang,Panzhihua,Guiyang,Tongling,Huzhou,Shaoxing,Zhoushan,and Ezhou,was in a declining stage and was affected to varying degrees by changes in pure technological efficiency,scale efficiency,and technological progress.The increase in green efficiency of water resources in the middle and lower reaches of the Yangtze River Economic Belt is driven by the optimization of technological efficiency and technological innovation;The main factor contributing to the increase in green efficiency of water resources in upstream areas is the optimization of technological efficiency.In addition,the green efficiency of water resources in45 cities along the Yangtze River Economic Belt was in a declining stage from 2014 to 2015,while the green efficiency of water resources in other years was in an upward stage compared to the original level.(3)Among the 45 cities along the Yangtze River Economic Belt from 2010 to 2019,the water-saving potential,sewage reduction potential,and industrial wastewater reduction potential were divided into three intervals: "low,medium,and high".The 45 cities along the line were also divided into five types: "three high,two high,one high,medium,and three low".Four cities,including Yueyang,Ma’anshan,Huangshi,and Jingzhou,belong to the "three high" type;In terms of spatial pattern,cities with the "three low" potential for water-saving and emission reduction exhibit a clustering pattern of "large settlement,small scattered".The watersaving and emission reduction potential of nearby cities is influenced by each other,and to some extent,there is a spatial spillover effect;In terms of time variation,the number of cities with the "three low" type has been showing an increasing trend during the research period,while the number of cities with the "three high" type has been decreasing significantly before 2012,and has been relatively flat since 2012.Based on the above conclusions,this paper proposes corresponding policy recommendations in three aspects: efficient cities should break through existing technological bottlenecks,inefficient cities should adopt differentiated policy measures based on water conservation and emission reduction potential,and regional water resource green efficiency improvement.To promote the rational development and utilization of water resources in cities along the Yangtze River Economic Belt and achieve high-quality green development in the region. |
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