Influence of the floods from different sediment source areas on the relationship between discharge and sediment concentration of the lower Yellow River

Based on the measurements during 1950-1960 and 1974-1985,the analysis are made on the influence of the floods from different sediment source areas on the relationship between the discharge and the sediment concentration at stations of Huayuankou,Caocun,Aishan and Lijin on the lower Yellow River. When the runoff between Hekou and Longmen,Malian River and Beiluo River accounts for rmre than 20% or 25% of the total water wlumes at stations of Sanmenxia,Heishiguan and Xiaodng,the flood is referred to as from the coarse sediment source area of the Yellow River. When the runoff between Hekou and Longmen,Malian River and Beiluo River covers less 20% or 25% of the total runoff at stations of Sanmenxia, Heishiguan and Xiaodong,the flood is referred to as from the fine-sediment source area or from the area with small sediment concentrations. As a result,the relationship between the mean discharge and the mean sediment concentration at stations of Huayuankou,Caocun,Aishan and Lijin on the lower Yellow River is divided into two classes:(1) the mean sediment concen-tration increases greatly for small variation in the mean discharge,and (2) the concentration does not increase much even when the mean discharge increases by several times. Meanwhile,the flood between Hekou and Longmen,Malian River and Beiluo River causes great increase in the mean inflow sediment coefficient and the mean sediment concentration of the lower Yellow River and consequently leads to a large amount of the deposition.