Research On Integrated Assessment Of Aquatic Ecological Environment Of Yue River Basin

Yue River basin is located in the central Ankang city, Shaanxi Province, stepping acrossHanyin County and Hanbin District of Ankang city. Due to the hospitable climate and theimportant geographical position, this basin is gradually rapid developed in recent years, whichcauses a threatening on eco-environment. In order to prevent further deterioration of theenvironment in this basin as well as provide practical and effective measures for the futuredevelopment, it is necessary to explore an integrated approach combining quantitative andqualitative methods for studying the situation and the changing of aquatic ecologicalenvironment in the basin, which would safeguard healthy life and promote sustainablesocio-economic development.Through studying the literature on aquatic eco-environment at home and abroad, also anon-the-spot investigation and the amount of related documents, this thesis is to devide intotwo subsystems based on the most serious problems of aquatic ecological environment in thebasin currently, which are water quality evaluation and risk assessment on geological hazards.Besides, through the application and analysis of different evaluation models, it aims at gettinga reasonable assessment result separately for each subsystem so as to select the pessimisticevaluation method as the final comprehensive approach. As far as the different mathematicaltheories and methods used in the course of the research, they can help find the potential rulesamong data as well as compare and explore the quantitative or qualitative methods forsupporting the evaluation results and providing rational ways in the same type research. Themajor conclusions are as follows:(1) In water quality evaluation: first, using rough set theory eliminates complexinformation and dependency among data, and determine the evaluation indicators and theircorresponding weighting coefficients; Subsequently, to eliminate the possible impact onevaluation results due to the different index weight values from different methods, fix indexweight values, and use three mathematical models for water quality assessment; Finally, selectthe optimal solution through contrast and comparison of different evaluation results.The three models are attribute recognition model, grey correlation model, and fuzzy greymodel respectively. Considering the first model, its unique concepts of "ordered partition" and "confidence criterion" improve the overall precision of evaluation results. As far as the othertwo, they judge the relationship between samples and evaluation levels from the perspectiveof membership degree, even though few deviation may be found, the most of results areaccurate. Therefore, they could serve as reasonable references in study to justify the accuracyof other methods.Final result of assessment: the water quality of Yue River, the mainstream of the basin, isthe worst, as level IV; Apart from one is heavier level III among the primary tributaries, therest are level II; The overall band of secondary branches is better, as level II; Finally, due tointensive factories and outlets for discharging sewage at the junction of the basin which isactually the boundary between Hanyin County and Hanbin District, water pollution is quiteserious, as level IV.(2) In risk assessment on geological hazards: extension theory regards the objectiveworld as a complex and interrelated network through the “matter-element”. Thus, multiplevariables can be integrated as one matter-element to analysis, so the issues can be solvedfrom both the quantitative and qualitative perspective. Differed from the last chapter, this partplans to fix the calculation model while change the means of getting index weight values, thenchoose the optimal solution through comparison the relationship between several results.Choosing three weighting methods to improve extension model, they are AHP as asubjective weighting method, entropy as an objective weighting method, and optimalcombination weighting method which can not only use the experts’ judging experience, butalso take advantages of objective data themselves. However, the results show that althoughthe principle of various weighting means are completely different, the final assessment resultsbased on correlation degree and maximum relevance of extention theory remain the same. Itindicates that, to some extent, the accuracy of extention theory itself can weaken the impact ofweight values, therefore, the results are more accurate.Final outcome of assessment: Yue River Valley area including the mainstream Yue Riverhas the highest risk, as level IV; Qinlin Lower Mountains area containing parts of thesecondary tributaries and the primary tributaries, has lower danger as level III, and the sameas two sides of Heng River; the risk of Phoenix Mountain protection area where partialsecondary tributaries located is level II; Finally, two sides of Fujia River which is one of theprimary tributaries has the lowest risk, as grade I.(3) In order to integrate both results of the two subsystems objectively and effectively,from the perspective of human and biological living circumstances, we establish pessimisticassessment system for aquatic ecological environment of Yue River basin. The pessimisticassessment is what takes the bad situation from various results so as to determine the level of aquatic eco-environment within each area and satisfy basic survival needs both for humansand creatures. Thus, it can provide some guidance and reference for watershed management,policy plan and future projects’ construction.Ultimate results of aquatic eco-environment assessment: First of all, Yue River Valley isworst area with category IV; Secondly, both Qinlin Lower Mountains area and two sides ofHeng River are better in rank, as class III; As a contrast, Phoenix Mountain protection areaand two sides of Fujia River have the best aquatic eco-environment situation within the wholebasin, as class II. Abviously, the current situation of aquatic eco-environment in this basin isnot optimistic, therefore, there is an urgent need to be increased and improved the aquaticeco-environment. In addition, through analysis and comparing with relevant documents, it canbe confirmed that the integared assessment is objective, reasonable and authentic as well.Finally, according to the integrated assessment results and the characteristic of each area,summarize the current five assessment units into four function districts, which are SensitiveDistrict, Conservation District, Recovery District and Open District. Based on this, putforward some constructive measures. Besides, The most important is that the result of thisthesis can promote comprehensive management and future engineering construction withinthe basin, which would guarantee fit life and promote sustainable development.