近60 a来长江干流输沙量变化及原因分析

根据长江干流宜昌、汉口、大通3个站点1954~2013年的输沙量数据，采用有序聚类和泥沙归因诊断分析等方法分析了3个站点输沙量时间序列的跳跃点以及降水、产流、产沙等各因素在输沙量变化中的贡献和作用。分析结果表明：3个站点的输沙量均存在明显的跳跃点，在跳跃点前后，输沙量出现较大幅度的下降，产沙能力的下降对输沙量比例变化率的贡献超过90%。人类活动造成的水库总库容量变化和长江流域植被覆盖度变化是造成长江干流输沙量变化的主要原因。结果表明：1985~2000年相比1954~1984年输沙量下降的585%、2001~2013年相比1985~2000年输沙量下降的831%是由于水库建设所造成。研究时段内流域植被覆盖度呈现先下降后上升的趋势。与1954~1984年相比，1985~2000年长江流域植被覆盖度下降，造成的输沙量变化为输沙量实际下降的 -436%，与1985~2000年相比，2001~2013年长江流域植被覆盖度上升，造成的输沙量下降贡献了输沙量实际下降的180%。 关键词： 长江；输沙量；突变点；人类活动

Analysis on the Change of Sediment Discharge of the Yangtze River in Recent 60 Years

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.