Characteristics of Flow and Sediment Change in Yangtze River in Recent 50 Years

In this paper,the flow and sediment change characteristics in the Yangtze River Basin in recent 50 years was studied.Seeing from the long-term average runoff and sediment transportation,the flow and sediment distribution is very unbalance in the upstream of the Yangtze River.For example,from Shigu to Yichang,the sediment discharge is increasing along the reach,and in the downstream of the Yichang station,it reduces along the reach,and the nominal diameter of the suspended load thin down accordingly.From 1991 to 2002, the runoff at the control stations has almost no change,but the sediment discharge reduced evidently.From 2003 to 2010,the reducing trend of the sediment discharge from the upstream of the Yangtze River is still continuing,and together with the function of the Three Gorges Reservoir(TGR),the sediment discharge downstream the dam reduced with large extent,and accordingly,the grain size of the suspended load coarsen along the reach,up to Jianli station,the coarse sand capacity has almost resumed to the level that before the impoundment of the TGR.After the impoundment of the TGR,new change occurred to the runoff distribution, sediment source and composition in the middle and downstream of the Yangtze River.The flow and sediment diversion capacity continues to decrease,and the sediment deposition velocity in the Dongtinghu Lake slows down.The TGR not only changed the erosion and deposition environment,but also accelerate the adjustment of sediment distribution situation in the middle and downstream of the Yangtze river.