Study On Evaluation Index System And Evaluation Method Of River Naturality

Rivers play a very important role in ecological protection in China,and also play an irreplaceable role in water cycle,material exchange and climate regulation.But for a long time,human beings in order to better pursue their own interests,to transform nature,resulting in serious man-made damage to the river ecosystem,the most common situation is the pollution of river water quality.In recent years,river near-natural management came into being,and the evaluation of river status can provide the target basis for managers and decision makers to make better use and management of rivers.Based on the key technology and demonstration research project of green ecological corridor operation and maintenance in Yongding River(Beijing section),this paper takes the Beijing section of Yongding River as the research object,through consulting literature,field sample survey and indoor data processing analysis,and combining with relevant experts' opinions,constructs a system of river natural evaluation,carries on the natural evaluation to Yongding River,and compares the different evaluation methods,the main research contents and conclusions are as follows:(1)Thirty-two candidate evaluation indexes were obtained according to the principle of index construction,and the candidate indexes were selected by principal component factor analysis,Pearson and Spearman rank correlation analysis.(2)The collected evaluation data are first standardized,and the weight relation of different evaluation indexes is determined by the combination of AHP and entropy weight method.That is,the index weights of the criterion layer are: hydrological elements(0.194),river morphology(0.216),physical and chemical properties of water body(0.202),riparian condition(0.258),and social ecological value(0.130).(3)Ranking of 35 survey sections.There are 3 natural reach,7.5 km,about 8.57% of the total length;10 near natural reach,25.0 km,about 28.57% of the total length;16 degraded reach,40.0 km,about 45.71% of the total length;6 artificial reach,15.0 km,about 17.14% of the total length.The evaluation results show that the Beijing section of Yongding River is degraded,but it still has potential near-natural restoration capacity.(4)Using fuzzy comprehensive evaluation method,grey correlation analysis method and principal component analysis method to evaluate the naturality of the river in Beijing section of Yongding River,the results are basically consistent with the actual situation of the river.Based on the stability and reliability of the method,grey correlation analysis and principal component analysis are better than fuzzy comprehensive evaluation.