中文摘要：

由于自然地理条件的差异,黄河上游（兰州至头道拐河段,以下简称兰头河段）具有十分显著的水沙异源特征,这对于河道冲淤有深远影响.本文以实测资料为基础,建立冲淤量与异源水沙之间的定量关系,为减淤措施的确定提供参考.划分了3个水沙来源区,即兰州以上清水来源区、祖厉河和清水河多沙细沙来源区和十大孔兑多沙粗沙来源区.基于清水区的汛期来水量与多沙细沙区、多沙粗沙区来沙量的对比关系,提出了不同来源区水沙的耦合指标,这些指标反映了清水区汛期来水对多沙区高含沙洪水的稀释作用.建立了兰头河段的年冲淤量SL-T与不同来源水沙量之间的多元回归方程,并按半偏相关系数的大小估算出兰州站汛期径流量Qwh,L、兰州站年输沙量Qs.祖厉河和清水河年输沙量Qs,ZQ和十大孔兑年输沙量Qs,KD对于SL-T变化的贡献率,分别为39.6％,23.8％,14.0％和22.6％.兰州汛期径流量对于兰头河段冲淤的贡献率居第一,十大孔兑的贡献率超过多沙细沙区.两个多沙区来沙贡献率之和为36.6％,为干流来沙贡献率的1.41倍.建立了兰头河段河道冲淤量与不同来源区水沙耦合指标的关系,并计算出使该河段达到冲淤平衡的临界值.这一临界值对于冲淤调控有一定的应用意义.基于本研究的成果,提出了减淤对策：（1）改变龙羊峡水库现有运用方式来增大兰州站汛期径流量;（2）在祖厉河和清水河多沙细沙区加强水土保持,减少从多沙细沙区进入干流的泥沙量;（3）在十大孔兑多沙粗沙区加强水土保持和进行风沙治理,减少输入黄河的粗泥沙量.

英文摘要：

Due to the difference in physico-geographic settings,the decoupling of water and sediment sources in the upper Yellow River basin is marked,namely,the main source area of runoff does not coincide with the main source area of sediment.This has a profound influence on channel sedimentation processes in the Lanzhou-Toudaoguai reach.The purpose of this paper is to establish the quantitative relationship between the channel sedimentation （SL-T） and different water and sediment source areas,whereby providing some reference to the decision-making for sedimentation reduction.Three water and sediment source areas have been identified,the clear water area below Lanzhou （Area 1）,the fine sediment source area of the Zulihe and Qingshuihe Rivers （Area 2）,and the coarse sediment source area of the ＂10 kongdui＂ （Area 3）.The water-sedi-ment coupling indices between the three areas have been proposed,which can be used to reflect the dilution effect of the clear water from Area 1 on the sediments from Area 2 and Area 3.A multiple regression equation has been established that relates the annual SL-T with suspended sediment load and runoff from different source areas.According to the semi-partial correlation coefficients of the influencing variables,the contributions of the high-flow season runoff （Qwh,L） from Area 1 and the annual sediment quantities from Area 1 （Qs,L）,Area 2 （Qs,ZQ） and Area 3 （Qs,KD） to the variation in the channel sedimentation have been estimated as 39.6％,23.8％,14.0％ and 22.6％,respectively.The contribution from Qwh,L ranks the first,the contribution from Qs,KD is larger than that from Qsh,ZQ,and the sum of the contributions fromQs,ZQ and Qs,KD is 1.41 times as large as the contribution from Qs,L.The relationships between SL-T and the water-sediment coupling indices have been established,based on which the threshold for no fill,no scour state of the channel has been estimated,which may be used for the SL.T adjustment through the reservoir regulations.According to the r