中文摘要：

通过对黄河宁夏河段下河沿、青铜峡、石嘴山3个水文站近60 a来实测水文泥沙资料的分析，运用统计分析方法，研究了黄河宁夏河段水沙变化特性以及河道冲淤情况，尤其是龙羊峡、刘家峡水库投入运行后所带来的影响。在此基础上，从输沙率与流量、汛期和非汛期输沙量与水量的关系探索了维持青铜峡—石嘴山段河道冲淤平衡的临界来沙系数和分粒径临界来沙系数。结果表明：（1）龙刘水库联调对宁夏河段来水来沙量影响较大，以下河沿站为例，来水量与来沙量呈减少趋势，且减少主要发生在汛期，输沙量减幅大于来水量减幅；青铜峡—石嘴山段汛期临界来沙系数为0．00236 kg·s／m6；粗、中、细沙的临界来沙系数不同，其中细沙的临界来沙系数最大，中沙和粗沙的相近。

英文摘要：

By analyzing the historical hydrology and sediment data in recent 60 years of Xiaheyan,Qingtongxia and Shizuishan hydrologic sta-tions,we studied the flow and sediment process and the river’s erosion and deposition using the statistic analyzing method. We highlighted the study of the influence of the operation of Longyangxia and Liujiaxia. On this basis,from the relations of sediment transport rate and flow discharge,flood season and non-flood season’s sediment and water amount,we explored the overall and size distinguished critical incoming sediment coefficient of QS section（shortly for the section from Qingtongxia to Shizuishan）. The result shows that the joint regulation of Longy-angxia and Liujiaxia has a great influence on the flow and sediment in Ningxia section. The incoming sediment coefficient of QS sections is 0. 002 36 kg·s/m6 ,and it’s different for coarse,medium and fine sand. Among the three size- distinguished critical incoming sediment co-efficients,the fine sand is the largest and the coarse and medium sand are similar,meaning that transporting fine sand requires the least flow discharge and the others are almost the same.