Simulation methods of bankfull discharge in the Lower Yellow River
Under the background of water and sediment variation in the Yellow River Basin,accurate calculation of the bankfull discharge of the lower Yellow River is crucial for predicting the trend of river erosion and sedimenta-tion and controlling the suspended river.On the basis of comparing and analyzing multiple existing methods for cal-culating the bankfull discharge in the lower Yellow River,this article first establishes a delayed response model for bankfull discharge considering the effect of non-flood season water and sediment conditions.Then,a simulation method for bankfull discharge based on delayed response model and energy method is proposed.The results show that:(1)the significant changes have occurred in non-flood season water and sediment conditions after the opera-tion of the Xiaolangdi reservoir.Among the three methods proposed in previous studies for calculating the bankfull discharge in the lower Yellow River,the sliding average method,delayed response model,and energy method are all unable to effectively simulate the bankfull discharge in the lower Yellow River after 2000.(2)A delayed re-sponse model considering the effect of non-flood season water and sediment conditions has been established to re-flect the impact of non-flood season water and sediment conditions since the operation of Xiaolangdi Reservoir.Al-though the simulation accuracy of bankfull discharge has been improved,some parameters in the calculation formula for the balance value of bankfull discharge have significant differences and the structural form is unstable.(3)Drawing on the advantages of the energy method,the formula for calculating the equilibrium value of bankfull discharge has been improved.The improved bankfull discharge calculation method can not only reflect the impact of annual incoming water and sediment,but also simultaneously reflect the effect of bed resistance represented by the median particle size of bed sediment.The new method not only has a certain theoretical basis,but also improves the simulation accuracy of bankfull discharge.
Lower Yellow Riverbankfull dischargewater and sedimentmedian size of bed sedimentdelayed responseenergy method
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