Study On The Variation Law Of Sediment Deposition In The Three Gorges Reservoir Area Under The Condition Of New Water And Sediment

Reservoir sedimentation is one of the focus and difficult issues at home and abroad,and has a significant impact on riverbed landform evolution,engineering operation and scheduling,and ecological environment.The sedimentation problem in the reservoir area of the Three Gorges Project in China is the focus and difficulty of widespread concern.Since the storage of water storage in the Three Gorges reservoir area in 2003,sediment deposition in the reservoir area has presented new sedimentation in the new water and sediment environment.trend.How to more accurately understand the sedimentation mechanism in the reservoir area and reach a new balance of erosion and siltation,which will have a direct impact on the dam operation scheduling,effective storage capacity,etc.This is an urgent problem to be solved in the sedimentation of the Three Gorges reservoir area.In order to analyze the sedimentation of sediments in the reservoir area,this paper discusses the trend of water and sediment change after dam storage,the total amount of sedimentation in the reservoir area and the sedimentation morphology along the path.Combined with on-site measurement experiments,numerical simulation calculations,etc.The causes of sedimentation,the change of hydraulic conditions and the physical process of sediment movement after dam storage are described separately.On this basis,the sedimentation discriminating model suitable for the mountain rivers in the Three Gorges reservoir area is proposed,and the following conclusions are drawn:First,the influencing factors of sediment flocculation in the reservoir area were analyzed by on-site measurement experiments.The results show that the chemical composition of sediment in the Three Gorges reservoir area after water storage,the influence of salinity,organic matter,pH and temperature on the sediment flocculation in the reservoir area can be neglected.Secondly,through the analysis of the data before and after the impoundment in the Three Gorges reservoir area,the results show that the water runoff after the impoundment of the Three Gorges Reservoir has no obvious change trend compared with that before the reservoir,and the sediment suspended sediment is reduced compared with the amount of sand coming from the reservoir.The particle size of the sediment in the reservoir is thinner,and the median particle size of the sediment in the reservoir area is below 0.01mm.The sedimentation amount in the reservoir area from 2003 to 2014 is 1.554 billion tons,which is calculated based on the section method from 2003 to 2012.The actual sedimentation in the reservoir area was 1,292.6 million m3,accounting for 94.6%of the total siltation in the reservoir area.Thirdly,through the on-site measurement experiment and the indoor flocculation and sedimentation velocity analysis in the reservoir area,based on the understanding of the physical process of the actual sediment movement in the river channel,two sedimentation discrimination modes in the reservoir area are proposed.The one-dimensional model of sediment transport in the reservoir area was established by using the sand silting sedimentation discriminating model,and the siltation of the Three Gorges reservoir area(2015?2065)was calculated to be 3.384 billion tons.