Abstract: Annual sediment data (from 1954 to 2013) at Yichang, Hankou and Datong stations are analyzed by the order cluster analysis and sediment identity factors decomposition methods to find the turning points in the time series of the sediment discharge data.The contributions of different factors to the relative change of sediment load are also studied. Results show that obvious turning points exist in the sediment discharge data at all the considered stations. Sediment discharge decreases significantly before and after the turning point. The decrease in the sediment concentration accounts for over 90% of the reduction in the sediment discharge at the three stations. Reservoir construction and vegetation coverage changes are the main causes for the decrease of sediment discharge in the Yangtze River.Our study shows that reservoir construction accounts for 585% of the total reduction in sediment discharge compared with the data from 1954 to 1984 and from 1985 to 2000; and 831% of the total reductionin sediment discharge compared with the data from 1985 to 2000 and from 2001 to 2013.The vegetation coverage decrease causes a -436% change in the sediment discharge compared with the data from 1954 to 1984 and from 1985 to 2000.Compared to the situation in 1985-2000, the increase in the vegetation coverage accounts for 180% of the total sediment discharge reduction in 2001-2013.
Key words：Yangtze River; sediment discharge; turning point; human activities