确定了黄河下游河道处于泥沙存贮-释放临界状态的水沙临界条件。当场次洪水平均含沙量小于31.68 kg/m3,或者来自中游多沙粗沙区场次洪水来沙量小于4 543×104 t,下游河道将由泥沙存贮状态变为泥沙释放状态。当河口镇以上清水区径流占场次洪水总径流量比率大于0.70时,也会由泥沙存贮状态变为泥沙释放状态。场次洪水泥沙输移比随洪水平均流量的增到而增大,流量为4 000 m3/s(相当于平滩流量)时达到峰值,此后有所减少。这表明,平滩流量时泥沙存贮最少,低于平滩流量和高于平滩流量时泥沙存贮均增大。
Based on data from the Huanghe (Yellow) River, the sediment storing-releasing process in an alluvial channel has been studied. The results show that in a hydrological year, sediment storing occurs during the high-flow season and sediment releasing occurs in the low-flow season. The amount of sediment storage in the high-flow season exceeds that of sediment release in the low-flow season, and net storage is positive for the whole year. Some thresholds for the critical storing-releasing state of the channel have been identified. When the event average suspended sediment concentration is smaller than 31.68 kg/m3, or the event sediment amount supplied from the "coarse sediment producing area" is smaller than 45.35?106 t, the channel would change from a state of sediment storing to sediment releasing. When the ratio of event water amount supplied from the "clear water source area" in the upper Huanghe River to the event total flood water is high than 0.70, the channel would also change from a state of sediment storing to sediment releasing. The event sediment delivery ratio (Rsd) of lower Huanghe River channel increased with the event mean water discharge (Qmean) to a peak, at which Qmean=4 000 m3/s, roughly equaling the bankfull discharge, and then Rsd decreased. This indicates that channel sediment storing is the least at bankfull discharges, and when Qmean is larger or smaller that bankfull, sediment storing increased.
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