Quantitative Research On Environmental Bearing Capacity Of Small Town In Three Gorges Reservoir Areas

With rapid growth of economy of small towns in Three Gorges reservoir area, environmental pollution is deteriorating day by day.How to coordinate economic development with environment, which is a much-needed solution to the problem. As the EBC (Environmental Bearing Capacity) to reflect the relationship between economic developtment and environmental system,the research of EBC to achieve sustainable development of small towns have a certain significance. As for the complexity of environmental system of small towns, it is difficult to measure the impact of human activities on the environment,and quantitativ eresearch of environmental carrying capacity is even more difficult.Based on previous studies,this paper defined the EBC of small towns of the concept,features, functionality in theory,and further researched the mechanism of the EBC of quantitative methods.Base on a full consideration in a comprehensive analysis of resource, environment subsystem,economy and social environment system features in small towns of Three Gorges reservoir,factors impacting EBC were found. An index system composed with four components of target layer, criteria layer, field layer and indicator layer was built up to evaluate EBC of these towns,which is concluding 30 specific targets and has been given weight with AHP.With the basic principles of state-space law and logistic curve,two conceptual models of the structure and function of small towns'environmental system have been proposed. A model was built up to calculate towns'environmental carrying level with the composite index value of the "law of multiplication".In accordance with certain criteria, Synthetic Index of Environment Bearing Capacity (ECSI) in small towns is divided into crisis, alert, general and good state of the four grade rating.According to the industrial structure, economy of scale and the ability of the different environmental pollutant,three typical of small towns were selected among Three Gorges reservoir area to do case studies that come to some conclusions.Due to ignore the environmental governance,economies of scale in Baishiyi town over EBC.Futher more,ECSI of the town is very low, only 0.382, in a state of crisis. Although the value of ECI(Index of Environment Subsystem Carrying Capacity) of Longtan town is relatively high, ECSI of the town is 0.484 and in a state of alert. ECSI of Youxi town is 0.605 and in a good state. Key factors of impacting ECSI of small towns include the following five aspects: capacity of carrying surface water pollutant, treatment rate of urban sewage, treatment rate of waste solid in urban, treatment rate of soil erosion, treatment rate of animal feces and utilization of straw. In response to these critical factors, combined with various of the actual situation of small towns , corresponding policies and measures have been proposed,which raise ESCI and promote the sustainable development.