Hydrodynamic Model Development And Application Of Medium And Small Rivers In Pearl River Basin

The Pearl River has second largest annual runoff in China with a large population,abundant water resources and developed regional economy.Since the 1990 s,floods have occurred frequently in the Pearl River Basin and have caused serious losses.Especially,in medium and small basins,the regional heavy precipitation increases,the peak discharge of flood season enhances,the frequency of short-duration flood events raises.Furthermore,the lack of hydrological data of medium and small basins restricts the flood forecasting and early warning to a certain level.All these factors make it a weak link in flood prevention and control.Compared with hydrological routing model,although hydrodynamic model demands more input parameters and massive calculation,it can better deal with complex braided water system,and can also simulate discharge,water level and other factors simultaneously.At present,most of the hydrodynamic models of the Pearl River Basin focus on the estuary Delta region.There are few simulations about Xijiang and Beijiang basins,and even less about the hydrodynamic model construction and research of the whole basin.This paper takes the Pearl River Basin as study area,extracts the digital river network according to the actual network,and develops the hydrodynamic routing model of the whole basin based on the solution of the Saint Venant equation.Taking the observed data of hydrological stations as input,the hydrodynamic model is simulated and validated in Beiliuhe River and Liujiang River basin.Coupled with Xin'anjiang hydrological model,the medium and small watersheds of Beijiang River and upstream Yujiang River are selected to simulate and analyze the hydrological process.The main results are as follows:1.The corresponding relationship between links and nodes of the digital river network in Pearl River is established.Combined with the water balance equation at nodes and based on the explicit finite difference method,the unsteady flow pattern of links is iteratively calculated.A one-dimensional hydrodynamic rouging model of the Pearl River Basin is therefore constructed.In order to ensure the stability of the simulation,variable time step calculation is adopted according to the flood wave movement in links and the change of nodes' water depth.Simple parallel algorithm is applied to make full use of the computer performance,which improves the calculation efficiency of the model.2.Based on the observation data in flood season,the flood process of hydrological stations in Beiliuhe River and Liujiang River is analyzed.The observed values are then used as input to simulate the flood process.Compared with the observation,the model can simulate the flood process well in both basins.Based on the simulated results,the discharge and velocity results of Yizhou,Sancha and Liuzhou stations in Liujiang River are further discussed.3.The medium and small rivers in the upper,middle and lower reaches of Beijiang River Basin are selected to carry out hydrological process research.The runoff characteristics of each river are analyzed according to the observed data of hydrological stations in flood season.The Xin'anjiang hydrological model is coupled with hydrodynamic routing model to simulate the hydrological process.The simulation of the model are close to the obeservation,the flood fluctuation characteristics are well performed,and the simulated results are reasonable,which can be further applied to the flood forecasting of medium and small rivers in this area.