Study On The Characteristics Of Water Flow And Topography Of Fish Habitat From Chaotianmen To Fengdu In The Upper Yangtze River

River habitats,also known as river aquatic habitats,are not only an important channel for humans to carry out periodic circulation,energy flow and utilization of natural materials in the biosphere,but also a space where various fish communities rely on for survival and reproduction.It is closely related to the environment and aquatic biodiversity.As an important cradle for the development of my country's freshwater fishing industry,the Yangtze River Basin has a large river basin,a vast drainage area,and a dense number of rivers,lakes and reservoirs.It is currently one of the river basins with the richest diversity of rare aquatic biological resources in my country and even in the world.With the rapid economic development,the construction of ecological waterways has become the development direction of the upper Yangtze River waterway construction.For this reason,the investigation and research of the river habitat before the construction of the waterway has become a top priority.In this paper,the Chaotianmen to Fengdu section of the upper reaches of the Yangtze River is selected as the representative section.Field surveys were carried out in the Chaotianmen to Fengdu section of the Yangtze River from 2019 to 2020,and the composition and distribution of aquatic organisms and fish resources were counted and identified.The relationship between river habitats and fish communities in the upper reaches of the Yangtze River is analyzed,and a scientific theoretical basis is provided for determining suitable habitats for fish in the upper reaches of the Yangtze River and river ecological protection and health management.Through the analysis of topography and geomorphology,the physical characteristics of topography and hydrodynamic factors of 20 fish habitats in the upper reaches of the Yangtze River from Chaotianmen to Fengdu were analyzed to determine the topography and hydrodynamic factors that affect fish habitats.The main research contents are as follows:(1)Through to the Yangtze river upstream fuling to video fish habitats and ecological environment survey,mastered the Yangtze river upstream fuling to video section of fish and its surrounding environment,the basic situation of the 49 species were identified,belonging to 4 orders,10 families,35 genera deepwater channel,the jet stream benthic and static water/slowly to the bottom is a major place for life fish,Shallow and deep pool river reach,channel bifurcation river reach and channel curving river reach are the main river reach of fish distribution in three fields.A total of 46species(genera)of 5 phyla of phytoplankton,27 species(genera)of zooplankton and28 species of macrozoobenthos were collected.(2)The physical characteristics of the different factors and their variation patterns along the river direction were analyzed.Among the hydrodynamic factors,the flow velocity can be used as a criterion for fish habitat in the whole river section,with values ranging from 0.4 to 1.0 m/s,while the Froude number does not have obvious characteristics;among the topographic factors,the wet perimeter and hydraulic radius can be used as a criterion for fish habitat in the whole river section,with values ranging from 564.5 to 1212.13 m for the wet perimeter and 13.04 to 38.92 m for the hydraulic radius;the water depth and overwater area can be used as a local criterion for fish habitat,with values ranging from 13.04 to 38.92 m for the difference in water depth.The values range from 564.5 to 1212.13 m for wet perimeter and 13.04 to 38.92m for hydraulic radius,and from 5 to 15 m for water depth and overwater area between5000-15000 m~2,while the width to depth ratio does not have obvious characteristics.(3)Based on the study area in the upper Yangtze river and the particularity of the position of the habitat,from each description of the upper Yangtze river topography and factors related to physical characteristics,according to different factors and the relationship of the natural ecology,fish scales and levels to choose and define describes the upper Yangtze river fish habitat river hydrodynamic and physical characteristics of the terrain.Protected area fish resources and data,hydrodynamic and topography of each physical factor in the upper Yangtze river fish habitat suitability situation has made the corresponding evaluation,according to its characteristics can be divided into the global or local level of impact factor,the secondary impact factor and no impact factors,including velocity,wet and hydraulic radius as the level of impact factor,Water depth and water crossing area were the second-order influencing factors,while Froude number and width-depth ratio were the non-influencing factors.