Study On The Influence Of Water Conservancy Project On Inflow Flood In Xueye Reservoir Basin

The topography and geological structure of the hilly area are complex,and heavy rainfall is prone to flood disasters.In order to achieve the purpose of flood control and disaster mitigation,the construction of a reservoir at the appropriate location can intercept the upstream water and play a role in flood storage and detention.The construction of the reservoir directly or indirectly affects the flood production and convergence process and reduces the accuracy of flood forecasting.In this paper,the Xueye Reservoir Basin is taken as the research object.A semi-distributed hydrological model of hilly watershed is established by using HEC-HMS model to simulate the process of rainfall runoff and flow evolution.By comparing the simulation results of two working conditions with and without reservoirs,the effects of water conservancy projects on inflow flood in Xueye Reservoir Basin are quantitatively analyzed.The main research contents and conclusions are as follows:(1)Using ArcGIS to process and analyze the DEM elevation data of the study area.According to the study area watershed characteristics,the SCS curve number method,SCS unit hydrograph method,Recession method and Muskingum method are used in the calculation model.Selecting 10 rainfall data and flow data from 1984 to 2016 to form a time series module.The Tyson polygon method is used in the meteorological module to determine the weight of the rainfall station.The reservoir module is added to the model,and the HEC-HMS model is used to construct the runoff and convergence model of the Xueye Reservoir Basin.(2)Ten flood runoff models were calibrated and validated.Six of them were used for parameter calibration and four for model validation.In this paper,the method of combining distributed sub-basin calibration with overall basin calibration is used to calibrate lumped parameters.Firstly,the subbasin parameters are calibrated by trial-and-error method,and then the whole watershed parameters are calibrated by Nelder and Mead optimization algorithm to obtain the optimal value of the global parameters.During the periodicity and verification period,the relative error between the calculated and measured peak flow is within 15%.Overall,the simulation results are in good agreement with the measured flow process,and each parameter meets the accuracy requirements.The model can be well applied to thecalculation of flooding in the study area.(3)Considering the single reservoir factor in the basin,the model of the small river basin is constructed and calculated.According to the calculation results,the reservoir intercepts the upstream water,which reduces the flood peak by 4.5%~33.7% and the peak time is delayed by 0.5~1.5h.For small reservoirs with the same water storage state,the distribution of rainfall schedule has a greater impact on the delay of peak time.When the rainfall schedule is short,the flood peak appears to be delayed.When the rainfall schedule is steeply steep,the peak time is postponed relatively small.(4)Keeping the model parameters unchanged,the two working conditions models in Xueye Reservoir Basin was calculated.According to the calculation results,reservoirs in the basin reduced the peak flow by 5%~15%,and the peak time was delayed by 0.25~0.75 h.The influence of water conservancy project on inflow flood in the same water storage state is closely related to the time-course distribution of rainfall.Short-duration and high-intensity rainfall,the peak time delay is shorter.The initial storage capacity of the reservoir is also a key factor affecting the peak and peak time of the river basin.The smaller the initial storage capacity of the reservoir,the stronger the ability of the reservoir to reduce the flood peak,and the greater the peak time delay.The reservoir changed the runoff generation and concentration mechanism of the original natural environment,which reduced the flood peaks and floods in the basin,delayed the peak time,and played a role in flood control and mitigation for downstream villages along the river.Due to the difference in rainfall schedule and the initial water level of the reservoir,the impact of the water conservancy project on the inflow flood is also different.Therefore,for the forecasting and early warning of watersheds,the impact of the water conservancy project in the basin on the runoff process is a factor to be considered.