黄河枯水和断流对下游河道冲淤及防洪的影响

Influcence of the Yellow River Waterflow Cut-off and Low Water on the flood Protection and Erosion and Silt in the Lower Reaches

近几年，由于上游水库水量的调节与中游地区产沙、三门峡水库排沙不协调，汛期水少沙多矛盾突出。特别是中游产沙集中的高含沙洪水，得不到上游来水的稀释，形不成输沙强度高的较大流量的洪水，导致下游主槽严重淤积。非汛期沿程大量引水，艾山以上河段冲刷主槽的水量减少，艾山以下河道输沙水量减少。由于上段河道主槽严重淤积，虽然断流期间泥沙不进入断流的河段，但非断流时期排往断流河段的水流含沙量增高，加重了非断流时期断流河段的淤积，使艾山以下河段汛期淤积加重，非汛期也无明显减淤，下游河道沿程行洪能力降低。

The contradiction of less water flow and much sediment in flood seasons are becoming more and moreevident in current years owing to the nonharmonious coordination in adjustment of reserviors in upperreaches with the sediment yield in the middle reaches and sediment discharge in Sanmenxia reserviors,especially because of the hrperconcentrated floods from the middle reaches which are unable to be dilutedby the water from upper reaches and can not form flood of large discharge of high capacity for sedimenttransPOrt, which leads to seriously silt in the lower reaches main channel. In the dry seasons, largevolume water drawing along the river resulted in the decrease of flow for main channel erosion in the reachesOf upper Aishan and reduction of water flow for river sediment transport in the reaches of lower Aishan.Because of the heavy silt in the upper channel, though the sediment did not enter the reaches of flow cut-off, there had been increased sediment content in the water delivered to the cut-off reaches in the non-cut-off periods that resulted in much more silt in the cut-off reaches and made critical silt in lowerAishan reaches in rainy seasons, and inevident silt reduction in dry seasons bring about lower floodtransporting capacity in the lower river channel.