Change of bankfull and bed-forming discharges in the Lower Yellow River

Based on the data of the Lower Yellow River from 1950 to 2003,this paper analyzes the change processes of the bankfull and bed-forming discharges and their response relationships to the runoff of Huayuankou Station.The result shows that the bank-full and bed-forming discharges decreased slowly in the past 50 years and they varied with the runoff of Huayuankou Station.The large runoff made large bed-forming discharge and the good bed-forming ability,and therefore caused large bankfull discharge.The comparison of the bed-forming and bankfull discharge shows that the bed-forming discharge was smaller than the bankfull discharge,and the channel shrinkage in the Lower Yellow River was resulted from the change of incoming flow.The research results furtherly suggest that one of the most efficient measures to increase the flood-conveying capacity of the Lower Yellow River should be to regulate flow processes released from Xiaolangdi Reservoir.