Analysis of Three Gorges Reservoir Water-sediment and the Period of Change of Temporal Series of Annual Runoff

According to hydrologic and sediment observation data,the flow and sediment features flowing into and out of Three Gorges Reservoir were analyzed systematically.By selecting representative hydrolagical stations located in the upper reaches of the Yangtze River,including mainstream and its tributaries,a comparative analysis on its changes of annual runoff,annual sediment yield,and annual average sediment concentration before and after the years of the Three Gorges Project starting water storage was conducted.In addition,based on the multi-resolution function of wavelet analysis,from the multi-time scale point,the time series of annual runoff data from 1950 to 2008 of Zhutuo,Cuntan and Yichang station was analyzed.The results indicated that the ratio of reservoir inflow volume to the multi-year average discharge changes little after the Three Gorges Project storing water,but the sediment concentration is significantly less than normal.In the past 50 years,the annual runoff time series of the upper reaches of the Yangtze River periodically varies,presenting as a cycle of abundance-low-abundance,and the dominant period is 12-year.At present,the incoming runoff of the upper reaches of the Yangtze River lies at a relative low status.