Comprehensive Assessment Of Eco-environmental Quality Of Zhangye City Based On GIS And Combination Weighting Method

Regional eco-environment is the kernel and foundation of sustainable development of regional economy and society. The regional eco-environmental quality symbolize the ability of sustainable development of regional economy and society, as well as the stability and coordinated degree between social production and human's environment. The regional eco-environmental quality and the problem of regional ecosystem security have become strategic questions attended universally by various countries, the eco-environmental system assessment also has become the front and the hot research area of correlative discipline.Deteriorating ecological environment and worsening quality of ecological environment have already become a great crisis of ecological environment in many areas across the whole country, which seriously restrict the development of regional economy. For fully knowing and understanding the regional eco-environmental condition, scientifically utilizing eco-environment correlated closely with human, comprehensively administrating eco-environmental problems in development, as well as correctly formulating regional development plan of national economy, we must thoroughly study eco-environmental quality which is one of important characteristics of regional eco-environment. But because the regional eco-environment is the giant and multiplex system composed by all kinds of parts which are both interdependent also relatively independent, currently it still is in the exploration to the comprehensive assessment of eco-environmental quality.The case chooses Zhangye city of Hexi corridor in Gansu province located in the northwest. The eco-environmental background of Zhangye is worrying, and the contradictory is incisive between regional development and eco-environmental quality. Because of lacking water, the regional eco-environment is friable. Mutual affection and influence between water resources and ecological environment have become the important restrictive factors which restrict regional sustainable development. The natural environment out of balance interweaves with the artificial environment increasingly worse, the ecological destruction coexists with environmental pollution, which are eco-environmental situation in this area. Therefore, studying the space and time changes of eco-environmental quality of Zhangye and analyzing impetuses of the space and time changes of eco-environmental quality, can provide theoretical basis for improving eco-environmental quality of Zhangye and formulating development plan of national economy.Main achievements in this paper are as flows.(1) Probes primarily into theoretical foundation, condition and developmental tendency of the research on regional eco-environmental quality.(2) With environmental ecology, landscape ecology, mathematical statistics and the sustainable development theory, the author sets up an index system of comprehensive assessment of eco-environmental quality of Zhangye.(3) Using remote sensing datas and statistical datas, the author constructs the background databases on eco-environment of Zhangye city based on ArcGIS8.3 in 1996,2000,2004, including natural environmental database, social economic database and database of eco-environmental pressure and response.(4) Comprehensively applying the subjective and objective methods for determination of weights of evaluating indicators, scientifically reasonably decides the weights of assessment index by combination weighting method based on analytic hierarchy process and entropy weighting method.(5) Carries on comprehensive assessment by applying the comprehensive assessment model of eco-environmental quality, determines the composite index of eco-environmental quality of Zhangye (in 1996,2000,2004) and quality subindex of various essential elements of ecological environment(in 1996,2000,2004), establishes the assessment database of eco-environmental quality in ArcGIS8.3 and various grade charts of indices on the base of quantitative analysis.(6) According to the assessment index of eco-environmental quality and the grade charts of quality index, analyzes spacial difference of eco-environmental quality in every year and every county. According to the grade charts of quality index and the dynamic degree model of quality index quoted for the first time, analyzes the dynamic changes and change degree of eco-environmental quality in every county from 1996 to 2004.(7) According to the assessment of eco-environmental quality of Zhangye, the main problems and the strategies of sustainable development are pointed out.(8) The research serves the administration and construction of ecological environment of Zhangye. Meanwhile, some concepts and methods used in the comprehensive assessment of northwest regional eco-environment are fit to assess other regions in some extent, and they can also be used for reference to homogeneous research.The study shows that, the overall eco-environmental quality of Zhangye is somewhat low. Except eco-environmental quality of Sunan is good, the eco-environmental quality of linze and Gaotai counties is bad, the eco-environmental quality of Gan Zhou district,Shandan and Minle Counties is ordinary. In the dynamic change of eco-environmental quality from 1996 to 2004, because decline rate of eco-environmental quality of Gaotai and Linze counties is higher than improvement rate of eco-environmental quality of others, the eco-environmental quality of Zhangye is on the decline. Differences in these counties are as flows. The eco-environmental quality of Shandan,Ganzhou district and Sunan counties have improved, and the improvement speed of Shandan county is far higher than others. The eco-environmental quality of Gaotai and Linze counties are on the decline, and the decline speed of the former is far higher than the latter.