Evaluation Model And Application Of Urban Water Environment Carrying Capacity

The water environment is the basic factor and important supporting force of the population,the social economy and the natural ecological environment system.However,with the growth of population some problems appearing in the process of rapid social and economic development,such as and extensive production,industrial structure,unreasonable layout and so on,water shortage and water environmental damage are also becoming more and more serious,which has restricted the development of social and economic.Although the water environmental protection work has achieved great results,the current water environment quality is generally good,but the water ecological damage to the river basin in some areas is still serious,the water environment quality is still deteriorating,and the water environment situation is still grim.As the natural attribute of water environment,water environment carrying capacity(WECC)is one of the important indicators to measure the sustainable development of a city.Therefore,the study of urban water environmental carrying capacity is of great significance for improving water environment quality,realizing the rational development and optimal allocation of water resources,improving the urban industrial structure,and maintaining the coordinated and sustainable development of urban and ecological environment.The Party Central Committee and the State Council attach great importance to the status and role of the water environmental bearing capacity in improving the water environment quality and promoting the construction of ecological civilization.The "Water Pollution Prevention and Control Action Plan"(abbreviated as "Water Ten Article")proposes to establish a monitoring and evaluation system for water resources and water environment carrying capacity,implement monitoring and early warning of bearing capacity,and complete the assessment of water environment carrying capacity of cities and counties in 2020.Based on the “Water Ten” task schedule and national environmental protection work requirements,combined with the development of water environment management,the Department of Water Environment Management of the Ministry of Environmental Protection has determined the assessment of water environmental carrying capacity,and identified Chengde,Zibo,Changzhou,Zhangzhou,Bijie and Yulin.The six pilot cities will first assess the water environmental carrying capacity,aiming to establish and improve assessment methods for water environmental carrying capacity,and to promote the use of the entire country.With the support of this project,this paper combines the achievements and experiences of previous studies to construct a set of evaluation models for water environment carrying capacity that can be promoted nationwide.First,the evaluation index system of urban water environment carrying capacity is constructed by "three step method".The first step is to determine a series of indexes of high frequency in the study of water environment carrying capacity through frequency analysis.Second steps are selected from 25 cities in southern China,North and Northwest China to analyze this series of indexes,and third steps are used to make grey correlation analysis on the results of principal component analysis,and the evaluation indexes of 14 water environment bearing capacity with national universality are determined.Secondly,the water environment carrying capacity was quantitatively calculated using the vector norm method.Furthermore,change trend of the water environment carrying capacity index was described.Finally,the simulation model was constructed based on the theory and method of system dynamics,simulating the development trend of water environment system under different development schemes and predicting the change of urban water environment carrying capacity index.This method is applied to the assessment of water environmental carrying capacity in Yulin,Guangxi Province,and water environment carrying capacity index of Yulin is predicted in the middle and long term.Based on the prediction results,combined with the current development situation and existing water environmental problems in Yulin,the countermeasures and suggestions for improving water environmental carrying capacity are put forward from three aspects: improving water resources utilization efficiency,strictly controlling pollutants entering the river and strengthening water environmental management.The evaluation model is successfully applied to Yulin,and puts forward rationalization proposals for improving its WECC,which verifies the scientificity of the evaluation model.The applicability of the index system makes the evaluation index easy to spread in the whole country.The quantifying of the index makes the quantification and evaluation of the water environment carrying capacity index operate.The regional difference and pertinence of the system dynamics model can reflect the different development structure of the city and provide theoretical basis for the sustainable development of its social and economic development.