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冲积河流平滩流量既反映了河道尺度上的水文-地貌耦合关系,又与流域因素密切相关。从这一概念出发,以黄河上游内蒙古河段为例,研究了平滩流量的变化,并在流域层面与河道层面上对其成因进行了研究。结果表明:上游水库调节改变了出库流量过程,使汛期流量大幅度减小,泄流过程均匀化,因而平滩流量减小。在龙羊峡水库修建后洪水流量减小导致漫滩机遇降低的情形下,泥沙淤在主槽内,也是平滩流量减小的重要原因。泥沙冲淤对于平滩流量的影响存在着某种累积或滞后效应,巴彦高勒平滩流量Qbf,BY不仅与当年的冲淤量有关,还与以前冲淤量有关,前4 a平均淤积量对平滩流量的影响最大。建立了平滩流量与前4 a累计淤积量、年均流量、年最大日流量的多元回归方程,该方程表明平滩流量既与当年的流量特征相联系,也与一定时间尺度上河道冲淤造成的后果相联系,反映了某种水文地貌耦合关系。研究还表明,存在着以下因果关系链:龙羊峡水库修建→汛期来沙系数增大→河道淤积加强→平滩流量减小。因此,通过改变龙羊峡水库的运用方式,增大汛期下泄流量,可以减小河道淤积、增大平滩流量,从而增大下泄洪水的能力,降低凌汛期间的防洪压力。平滩流量的变化是流域因素变化的结果,所建立的多元回归方程表明,在50 a的时间尺度上,暖干化指标的增大、引水率的增大、水库总库容的增大和天然径流系数的减小,是黄河上游平滩流量减小的原因。
The alluvial river flat beach flow reflects not only the hydrological-geomorphological coupling of the river scale, but also the river basin factors. Starting from this concept, taking the Inner Mongolia section of the upper reaches of the Yellow River as an example, the change of the flat beach flow was studied, and the causes of this phenomenon were studied at the basin and river level. The results show that the adjustment of the upstream reservoir changes the flow of the outflow, so that the flow in the flood season decreases drastically and the discharge process is uniform, so the flow of the flat beach decreases. In the case of the decrease of flooding flow after the construction of Longyangxia Reservoir, the sediment deposition in the main channel is reduced, which is also an important reason for the decrease of the flat beach flow. Sediment deposition has some cumulative or lag effect on the flat beach discharge. The Bayan Gul flat beach discharge Qbf, BY is not only related to the amount of scouring and silting in the current year but also related to the amount of scouring and silting. The average of the first 4 a The amount of siltation has the greatest impact on the flat beach flow. A multiple regression equation was established for the flat beach discharge and the accumulated sediment, average annual discharge and annual maximum daily discharge in the first 4 years. The equation shows that the flat beach discharge is not only related to the current flow characteristics but also to the scour and silting of the river at a certain time scale The consequences linked to the reflection of some of the hydrogeological coupling. The study also shows that there is a chain of causality: the construction of Longyangxia Reservoir → the increase of sediment yield in flood season → the increase of siltation in the river → the reduction of beach flow. Therefore, by changing the operation mode of Longyangxia Reservoir and increasing the flood discharge in flood season, the siltation of the river can be reduced and the flat beach flow can be increased, so as to increase the capacity of releasing floodwater and reduce flood control pressure during flood season. The change of flat beach flow is the result of the change of basin factors. The established multiple regression equation shows that on the time scale of 50 a, the warming and drying index increases, the water diversion rate increases, the total reservoir capacity increases and the natural runoff The reduction of the coefficient is the reason for the decrease of the flat beach flow in the upper Yellow River.