小浪底水库运行以来对黄河下游河道河床演变特性的影响

小浪底水库自1999年10月下闸蓄水，23年来深刻改变了进入黄河下游河道的径流泥沙过程，进而引起了下游河道的再造床。本研究以1960—2022年长序列水文泥沙、断面地形、遥感影像等多源资料为基础，从径流泥沙、冲淤演变、形态调整三个方面阐明了小浪底水库运行以来对下游河道河床演变特性的影响。结果表明：(1)水库拦沙效果显著，下泄水量在年内分配更加均匀、沙量则向汛期更加集中;大流量和高含沙事件的严重程度和发生频率均有所降低;悬沙调整不明显，床沙粗化显著。(2)扭转了黄河下游河道持续淤积的趋势，冲淤调整主要发生在花园口至高村的游荡性河段;冲刷效率持续下降，主槽过流能力得到显著恢复。(3)游荡性河段横断面形态向窄深发展，二级悬河发育得到有效缓解，整体河势处于相对稳定状态。研究成果丰富了多沙河流修建水库对下游河道影响的科学认识，也可为小浪底水库优化调度提供科技支撑。

Morphological effects of the operation of Xiaolangdi Reservoir on the Lower Yellow River in recent years

Since its operation in October 1999，the Xiaolangdi Reservoir has profoundly changed the process of runoff and sediment entering the lower reaches of the Yellow River for 23 years，leading to the reconstruction of the riverbed in the lower reaches.This study is based on multi-source data such as long-term hydrological and sediment，cross-sectional topography，and remote sensing images from 1960 to 2022.It elucidates the impact of the Xiaolangdi Reservoir on the downstream river channel since its operation from three aspects：runoff and sediment，erosion and sedimentation evolution，and morphological adjustment.The results show that：(1) The sediment retention effect of the reservoir is significant，with a more uniform distribution of discharged water within the year and a more concentrated sediment amount towards the flood season;the severity and frequency of extreme floods，droughts，and hyperconcentration events have significantly decreased;the adjustment of suspended sediment is not significant，and the coarsening of bed sediment is significant.(2) The trend of continuous sedimentation in the lower Yellow River has been reversed，and the adjustment of erosion and sedimentation mainly occurs in the wandering river section from Huayuankou to Gaocun;the erosion efficiency continues to decrease，and the flow capacity of the main channel has been significantly restored.(3) The cross-sectional morphology of the wandering river section has developed towards narrow and deep depths，and the development of secondary suspended rivers has been effectively alleviated.The overall river regime of the river section is in a stable state.The research results have enriched the scientific understanding of the impact of reservoir construction on downstream rivers in sandy rivers，and can also provide scientific support for the optimal operation of the Xiaolangdi Reservoir.