前汛期中小洪水小浪底水库调水调沙方式

Water and Sediment Regulation of Xiaolangdi Reservoir in Medium and Small Floods During Recent Pre-Flood Season

小浪底水库运用进入拦沙后期以来水沙偏枯,洪水期多采用蓄水拦沙方式运用,2007—2016年水库整体排沙较少,排沙比为26.7%,细沙排沙比约38.7%。前汛期是水库的主要排沙时段,排沙比为29.4%。分析认为,前汛期潼关站出现流量大于等于1 500 m^3/s持续2 d且含沙量大于50 kg/m^3的洪水过程时,小浪底入库沙量较多,2007—2016年满足条件的洪水仅出现5场,入库沙量占前汛期的72.5%;数学模型计算结果表明,上述洪水期间通过优化水库调度,可有效减缓水库淤积,同时下游河道淤积主要集中在小浪底—夹河滩河段,实测资料及前期研究表明淤积在小浪底—夹河滩河段的泥沙对河道影响不大,且在下次汛前调水调沙或者小浪底水库清水下泄过程中能够冲刷并向下游输送。

Since the Xiaolangdi Reservoir entering into the late stage of sediment control operation, because of its persistent low levels of water and sediment, water storage and sediment trapping have been the most commonly used modes of its operation during the flood season. From 2007 to 2016, the overall sediment discharge was low, with a sediment discharge ratio of 26.7% and fine sediment discharge ratio of approximately 38.7%. During the early flood season, which was when most of the sediment discharge took place, the sediment discharge ratio was 29.4%. Analysis results show that from 2007 to 2016, there are only five flood events with discharge greater than 1,500 m^3/s for two consecutive days and sediment discharge greater than 50 kg/m^3 occurred at Tongguan Station during the early flood season. The amount of inflow sediment during these five events accounts for 72.5% of the early flood-season sediment, making it an optimal time for sediment discharge and regulation. Simulation results demonstrate that the optimization of reservoir regulation during such flood events can effectively slow reservoir deposition, with most of the deposition in the lower Yellow River occurring in the Xiaolangdi-Jiahetan reach. Moreover, measurement data and previous studies show that the sediment deposited in the Xiaolangdi-Jiahetan reach has limited effect on the downstream channel, because it can be transported during the subsequent clear-water discharge from the Xiaolangdi Reservoir.