Numerical Simulation Analysis Of Sediment Deposition In Yazidang Reservoir And Study Of Sediment Regulation Scheme

Sediment deposition is one of the important factors that endanger the normal service life of the reservoir,especially in the area where the upstream flow carries sediment,a large amount of sediment enters the reservoir with the water flow,which will reduce the effective storage capacity of the reservoir and affect the normal operation of the reservoir.Restrain the economic and social benefits of the reservoir.The research object of this paper is Yazidang Reservoir in Ningxia,which undertakes the main water supply task in Ningdong area.In order to ensure the normal operation of the reservoir and the function of water supply and benefit,MIKE21,MIKE11 model is used to simulate the sediment transport and scouring and silting in the reservoir.Through the mutual verification and comparison of the measured data of the calculation results of the first and two dimensional models,the rationality of the model is verified,the siltation law of sediment in the reservoir area is obtained by analyzing the results,and the silting condition of the reservoir in the later stage of operation is predicted.In view of the siltation status of the reservoir in the water transmission channel and the reservoir area under different water level conditions,a reasonable optimization scheme is put forward,which provides the basis for the operation decision and optimal operation of the Yazidang reservoir in the later stage.The main research contents and achievements are as follows:(1)by using mathematical statistics method,the existing hydrological data of Yazidang Reservoir are calculated and analyzed,and the timely and empty distribution law of incoming water and sediment transport is obtained.Through the data collation,on the basis of the original topographic data,the two-dimensional and one-dimensional mathematical models are established by MIKE21 and MIKE11 respectively,the definite solution conditions are set,and the siltation form and suspended sediment distribution of the first stage reservoir are calculated.The comparison between the calculated water level and the measured water level verifies the accuracy of the hydrodynamic module,and calculates the terrain and compares it with the actual measured terrain.It mainly pays attention to the position of sediment deposition,the distribution of sediment and the change of topographic elevation.The suspended sediment distribution and outlet sediment concentration are compared and analyzed,and the rationality of the model is verified.(2)on the basis of the first stage simulation calculation,the water and sediment transport from the reservoir is designed to be normal and maximum.The time limit of one-dimensional simulation calculation is fast,so MIKE11 is used to simulate the later operation of the reservoir for 60 years.According to the design flood level interval of the first and second phase of the project,the sediment deposition and silting position of the water transmission channel and the reservoir area are calculated under different fixed water level operation conditions.Because the one-dimensional calculation results are the average value of the section,the siltation range and the highest siltation position of the sediment can not be refined and analyzed,so the two-dimensional model is combined with the simulation analysis.The sediment deposition in the reservoir area and the distribution of suspended sediment without siltation in the reservoir area are calculated by two-dimensional model.As Yazidang Reservoir is mainly responsible for the task of water supply,it focuses on the water quality of the export and whether to meet the water supply demand.At the same time,according to the calculation results of one and two dimensional model,the accuracy of the model is further verified(3)in order to ensure the normal operation and effective storage capacity of the reservoir,it is necessary to control the incoming water and sediment transport conditions of the reservoir so as to keep the water transmission channel flowing smoothly.Therefore,according to the prediction and calculation of the reservoir water transmission channel and the siltation condition of the reservoir area under different fixed water level conditions,the scheme of optimizing the reservoir operation and operation is put forward: first,to reduce the reservoir operation water level in the month of high sediment transport concentration,that is,to increase the sediment transport efficiency;Second,the high water level runs in the high sediment transportation month,which makes the sediment drop and silts,and lowers the reservoir operation water level to scour the sediment in the low sediment transportation month.Finally,through the comparison and selection of various schemes,according to the requirements of reservoir operation,the best scheme of reservoir operation and operation is recommended.