减缓宁蒙河道泥沙淤积方案及效果研究

Reduction Schemes Research and Effect Evaluation of Sedimentation in Ningmeng Reach of the Yellow River

通过对实测资料的分析,阐明宁蒙河道不同粒径泥沙来源及冲淤规律:细泥沙是宁蒙河道来沙的主体,主要来源于下河沿以上和宁夏支流,且细、中泥沙冲淤效率与水沙条件有较好的响应关系,随流量的增大河道淤积效率显著降低;而较粗泥沙和特粗泥沙在来沙量中比例较低,特粗泥沙主要来源于入黄风沙,多发生淤积且流量增大也难以提高输送能力。由此提出宁蒙河道减缓淤积的“拦粗排细”综合治理方案,水库调控恢复洪水过程输送细、中泥沙,水土保持和风沙治理拦减较粗泥沙和特粗泥沙。制定了多种减淤方案,并利用水动力模型进行了方案计算,表明各种单项措施减淤效果都有限,河道仍持续淤积,只有采用“拦粗排细”综合治理方案可使河道微冲,且包含水库调控恢复洪水过程的方案对内蒙古河段的减淤效果较好。

Based on the analysis of the measured data,the source of grouped sediment and the law of erosion and deposition in the Ningxia⁃Inner Mongolia reach of the Yellow River are showed that the fine sediment(d≤0.025 mm)is the main part of the sediment and comes from the upstream of Xiaheyan and the tributaries in Ningxia.The erosion and deposition efficiency of the fine and medium sediment(0.025 mm<d≤0.05 mm)are decreased significantly with the increase of discharge.The coarse sediment(0.05 mm<d≤0.1 mm)and extra coarse sedi⁃ment(d>0.1 mm)account for a small part of the sediment.The extra coarse sediment mainly comes from desert aeolian sand,which often de⁃posits and is difficult to improve the transportation capacity with the increase of discharge.Therefore,the comprehensive control scheme of“intercepting the coarse sediment and discharging the fine”for reducing sedimentation in Ningxia⁃Inner Mongolia reach is put forward,which the reservoirs are regulated recovering flood process to transport fine and medium sediment and water conservation and desert control are im⁃plemented to intercept coarse sediment and extra coarse sediment.The hydrodynamic model was used to calculate the effect of deposition re⁃duction schemes.It shows that the deposition reduction effect of various single measures is limited and the river channel continues to deposit.Only use the control scheme of“intercepting the coarse sediment and discharging the fine”can make the river channel slightly scoured and the schemes including reservoir regulation in the Inner Mongolia reach has a good effect on the flood restoration process.