三门峡水库典型运用时段黄河下游粗细泥沙的输移和调整规律

Transportation and Adjustment of Different Grain Sized Sediment Along the Lower Yellow River under Typical Operation Modes of Sanmenxia Reservoir

通过对黄河下游实测资料的分析 ,探讨了三门峡水库不同典型运用时段粗细泥沙的冲淤特点 。

The degradation and aggradation of the Lower Yellow River are affected by the operation modes of the Sanmenxia Reservoir. Under the influences of clear water or water of low sediment concentration released from the reservoir, the channel of the Lower Yellow River was eroded and the sediment concentration was recovered, but the concentration of fine sediment recovered slowly in a long distance, while the coarse and medium sediment recovered fast in a rather short distance. When the reservoir was flushed, the Lower Yellow River was serious silted because of the low discharge, high sediment concentration and coarse sediment sluiced from the reservoir. The quantity of siltation accounted for 60%～70% of the incoming sediment load, in non\|flood season, the channel of the Lower Yellow River was eroded by clear water from the reservoir. The eroded sediment from the channel bed was relatively coarse in the reach upstream of Huayuankou. The eroded coarse and medium sediment accounted for 30%～40% respectively with the median size of 0 04mm. The erosive distance was increased with the increasing of discharge. After the Spring flood, the capabilities of sediment transport for different sized sediment were decreased because of the armouring of the composition of the channel bed, and the quantities of eroded sediment were also decreased correspondingly. When the reservoir was flushed in pre\|flood season, the grain size of flushed sediment was 0.005～ 0.042mm. The deposition mainly occurred in the reach upstream of Huayuankou. The quantities of deposition for different sized sediment were determined by the incoming sediment and were not related to the incoming discharge. The grain size also was a significant factor affecting the quantities of deposition.