Research on new characteristics of runoff and sediment in Yichang-Wuhan reach of middle Yangtze River after TGR impoundment

The impoundment of the Three Gorges Reservoir(TGR) has changed the characteristics of runoff and sediment at the downstream of the dam.In order to research the new characteristics of runoff and sediment in Yichang-Wuhan reach of the middle Yangtze Rive after TGR impoundment,the variation tendency and sudden change of the runoff and sediment data of Yichang and Hankou hydrologic stations were analyzed with MannKendall method.The analysis results demonstrate that:after TGR impoundment,the water runoff process has been adjusted.The time in dry season has been shortened and that in median water period has been prolonged.Annual sediment discharge and some of monthly sediment discharge in the two hydrologic stations have changed suddenly,and the sediment passing into Yichang-Wuhan reach has been substantially reduced,so the water discharged from the dam can be ahnost thought of as water.Research shows unsaturated degree of the clear water released from reservoirs decreased after obtaining sediment along the river,so the sediment discharge would be partly recovered.