Change on Characteristics of Runoff and Sediment in the Main Stem of the Yellow River

Based on the data from hydrology stations,the change of characteristics of water and sediment was analyzed in terms of the amount,process,flood and sediment size grade in the main stem of the Yellow River since 1986 Results proposed in the paper show that the amount of runoff and sediment reduced greatly in flood season,the decrease of runoff along the river course in non-flood season becomes more and more serious,the opportunities of medium and large flood reduced enormously and dischanges at flood peaks become less and less.But the law of sediment composed has not changed in trend.These results could be a reference to the development and utilization of water resource and the harness of the Yellow River.