Study on Runoff and Sediment Process Variation in the Basins System of the Middle Reaches of the Yellow River

River sediment yield is the reaction of various natural factors and human action factor comprehensive role in basin, wash with sedimentation of river course to change, is related closely.Since 1970's, the Yellow River mainstream discharge and sediment yield load to occurred variation, which discharge of water and sediment yield load decrease apparently, the new condition of the river course of lower reaches occurs dwindlingly and break to flow.The cause of runoff and sediment yield process variation is studied according to used analysis method of the geography environmental factor and data from the Hekou town to Longmen area of the middle reaches of the Yellow River.The result shows that runoff and sediment yield load of basins from the Hekou town to Longmen area of the middle reaches of the Yellow River is related closely with geography environmental factor, the climate fluctuation with human activities influence reduce runoff and sediment in average to 53.4%, 28.6% and 46.6% and 71.4% respectively from 1970's to 1980's .