Sediment Transferring Function of the Lower Yellow Riveras Influenced by Discharge and Sediment Load Conditions

The sediment transferring function of the lower Yellow River has been studied in this paper by using a geomorphological approach. An index for sediment transferring function (F_s) of a river has been proposed, which is defined as the output of sediment load from a given river reach divided by the input of sediment load to this river reach. The F_s index was found to be closely related with discharge and sediment load conditions. When water discharge decreased and sediment load increased, F_s decreased. The 0.05mm percentage in suspended load was negatively correlated with F_s. The index C/Q, especially the index C_(0.05)/Q, where C is suspended sediment concentration, C_(0.05) is the concentration of the 0.05mm sediment, and Q is water discharge, is a major factor determining sediment transferring function of the lower Yellow River. The higher the C/Q and C_(0.05)/Q are, the lower the F_s will be. The event-based F_s decreased with both the increasing event maximum suspended concentration and the increasing frequency of hyperconcentrated flows. The construction of Xiaolangdi Reservoir provides some possibility for enhancing the sediment transferring function of the lower Yellow River by means of water discharge and sediment load regulation. This study shows that the event-averaged suspended sediment concentration C=35 kg/m~3 and the event-averaged index C/Q=(0.015 kg·s)/m~6 are the optimal values for the optimization of F_s, and so is the bankfull water discharge.