Multi-Scale Evaluation Of River Habitats In Taihu Lake Basin

River habitat is a comprehensive environment of aquatic plants and animals' habitats and neighbouring environments,providing a natural connection between the natural environment and various living beings,which is an important reference for river health assessment.Since the urbanization of the Taihu Lake Basin,river ecosystems have been strongly affected by various human activities,leading to serious degradation of river habitats,including water quality deterioration,river landfill and habitat loss.This paper sorts out the domestic and foreign literatures.Based on the two evaluation angles of river basin scale and urban river section scale and the combination of remote sensing data interpretation and field survey,the current situation and differences of river habitats in Taihu Lake Basin are studied to provide a scientific basis for habitat management and restoration.The main work content and conclusions of this paper can be summarized as the following aspects:(1)This paper defines the connotation,time and space characteristics and functions of river habitats,summarizes the evaluation theories,scales and model methods of river habitats in Western developed countries such as Australia,the United States and the United Kingdom and classifies and discusses the domestic empirical research from the perspectives of methodology and research scale.In order to provide enlightenment and reference for the establishment of multi-scale study of river habitat in Taihu Lake Basin,this paper attempts to study the river habitat of Taihu Lake Basin from the basin scale and urban river scale.(2)At the basin scale,this paper selects river geomorphic indicators and river network structural characteristics indicators(regional river network weighted curvature,box dimension,actual integration of river network,regional river slope,backbone river network density,river network complexity),based on the DEM elevation data of the Taihu Basin and the river network data of the Taihu Basin processed by ArcGIS and uses improved entropy weights meta-model to evaluate the river habitat quality in seven water conservancy areas(Huxi District,Zhexi District,Wucheng Xixi District,Yangchengdianyu District,Hangjiahu District,Puxi District,Pudong District)in Taihu Basin.(3)In the urban river scale,based on the British Urban River Survey(URS)evaluation system,the status and characteristics of river habitats in Taihu Lake Basin,this paper conducts on-the-spot investigations on the habitats of 50 typical cities in seven prefecture-level cities in Taihu Basin.There are 28 indicators in 4 aspects,including physical habitats and vegetation index,material index and pollution index.The Spearman rank correlation analysis and principal component analysis were used to screen the dominant indicators.The evaluation system of habitat quality index(SHQI)of urban river sections was established with reference to the URS rating.And the one-way ANOVA and independent sample T test were used to explore the differences between the urban river habitat quality status and the dry river tributary urban river habitat quality in seven prefecture-level cities.(4)The results show that at the basin scale,the river habitats in the Taih u Lake Basin have obvious spatial heterogeneity.The river habitats of the east ern plains in the Wuchengxi District,Yangchengdian District,Puxi District and Pudong District are all “poor”.The overall situation of river habitats in the w estern hilly areas is better than that of the eastern plains.The river habitat rati ng in the west of Zhejiang Province is “good”,and the river habitat rating in Huxi District and Hangjiahu District is “moderate”.At the urban river scale,th ere are 3 river sections with a “excellent” habitat level in 50 cities,accounting for 6%;6 with the “good” level,12%;27 with the “moderate” level,54%;9with the “poor” level,18%;5 with the “very pool” level,accounting for 10%.From the perspective of river habitat quality characteristics,the situation of th e vegetation index in urban river habitats in Taihu Lake Basin is good while t hat of the physical habitat and material index is bad.The overall situation of habitats is spatially represented as Zhenjiang>Huzhou>Hangzhou>Jiaxing>Suzhou>Wuxi>Changzhou.There are obvious differences between physical habitats,mat erial indices and pollution indices(P<0.05).Between the main stream and the tributary section,there is obvious difference in the material index and pollution index while no such difference in SHQI index(P<0.05).