流域产水产沙耦合对黄河下游河道冲淤和输沙能力的影响

Sedimentation and sediment transport in Lower Yellow River as influenced by coupling of water and sediment yield in upper drainage basin

在具有水沙异源特征的流域中,不同水沙来源区的来水来沙之间的关系,可以称为流域水沙耦合关系。流域水沙耦合关系通过流域侵蚀带与沉积带的耦合,会进一步影响沉积带的冲淤过程。对于黄河流域,提出以多沙粗沙区的来沙量和河口镇以上清水区的来水量之比来表示流域产水产沙搭配关系,称之为流域产水产沙耦合指标。无论是对于洪水系列还是对于年系列,黄河下游来沙系数、含沙量与流域产水产沙耦合指标之间都具有密切的关系。流域产水产沙耦合指标控制着下游河道的来沙系数、平均含沙量和最大含沙量,并进而影响河道冲淤量和河道泥沙输移比。黄河下游高含沙水流的发生与流域产水产沙耦合指标Iws之间有密切的关系。当Iws<0.314t/m3时,下游可不再发生高含沙水流。这启示我们,通过对多沙粗沙区来沙量和河口镇以上清水区来水量的控制,可以减少下游河道高含沙水流发生的频率。对于场次洪水而言,当流域产水产沙耦合指标Iws<0.2t/m3时,冲淤量、淤积强度变化很小,但当Iws>0.2t/m3以后,冲淤量、淤积强度迅速增大。本文的研究成果对于黄河流域的治理有一定的参考意义。通过对流域水沙耦合关系的调控,来减少下游河道的淤积,是一种可行的途径。

In a river basin where the runoff and sediment are delivered from different source areas,the relation between water and sediment from different source areas may be regarded as the coupling of water and sediment yield in the drainage basin.Through the coupling of erosion and sedimentation zones,the coupling of water and sediment yield in the drainage basin may further affect sediment deposition in the sedimentation zones.For the Yellow River,the ratio of the sediment yield from ＂the coarse sediment producing area between Hekouzhen and Longmen＂ to the runoff from ＂the clear water producing area＂ above Hekouzhen,referred to as Iws has been taken as an index for the coupling of water and sediment yield in the river basin.For either the series of flood events or annual series,the incoming sediment coefficient（C/Q,where C is the sediment concentration and Q is the water discharge） and the sediment concentration are closely correlated with Iws.The Iws controls the C/Q,the annual mean sediment concentration and the annual maximum sediment concentration,and also influences the channel sediment delivery ratio.The occurrence of hyperconcnetrated flows in the Lower Yellow River is closely related with Iws.When Iws is smaller than 0.314t/m^3,no hyperconcnetrated flows occur in the Lower Yellow River.Thus,through controlling the sediment yield in the drainage area between Hekouzhen and Longmen and river flow from the area above Hekouzhen,the frequency of hyperconcentrated flows in the Lower Yellow River may be reduced.For flood events,when Iws is smaller than 0.2t/m^3,the amount and intensity of sedimentation in the Lower Yellow River are low and vary slowly,but when Iws becomes larger than 0.2t/m^3,they increase rapidly.The results of this study can be applied to the river basin management of the Yellow River.Through the regulation of Iws by some measures,sedimentation in the Lower Yellow River may be eased.