湖南四水入洞庭湖水沙演变及成因分析

以湖南四水入洞庭湖的代表性控制站1951-2009年长系列水文数据为基础,运用Mann-Kendall趋势突变检验等方法探讨水沙演变过程并分析了其成因。结果表明:四水年径流量变化比较复杂,存在多个上升-下降过程,但总体上无明显上升或下降趋势;年输沙量总体上呈明显下降趋势,且突变时间存在差异,湘水是1996年,资水是1973-1974年,沅水是1997-1998年,澧水是1998年。年径流量的减少、植被覆盖增加以及大中型水库的建设等综合作用是2001年后年输沙量较大幅度减少的主要原因。

Changes of Runoff and Sediment Discharge into Dongting Lake from the Four Rivers in Hunan Province

On the basis of hydrological data from 1951 to 2009 of four representative gauging stations(Xiangtan,Taojiang,Taoyuan,Shimen),the changes of runoff and sediment discharge into Dongting Lake from the Four Rivers(Xiang River,Zi River,Yuan River and Li River) in Hunan Province were investigated using Mann-Kendall trend test,moving average value and double mass analysis.The results showed that annual runoff was highest in Xiang River(657 × 108m3),intermediate in Yuan River(640 × 108m3) and Zi River(229 × 108m3),and lowest in Li River(147×108m3).However,the changes of annual runoff of the Four Rivers were insignificant(P > 0.05),with several up-down processes.Annual sediment discharge was highest in Yuan River(1 051×104t),intermediate in Xiang River(959×104t) and Li River(382×104t),and lowest in Zi River(199×104 t).The annual sediment discharge from the Four Rivers showed a significantly decreasing trend generally(P < 0.001).Changes of annual runoff and annual sediment discharge were consistent in Xiang River before 1980s,in Zi River after 1960s,in Yuan River before 1980s and in Li River before 1990s.Moreover,the time of abrupt change in annual sediment discharge was different among the Four Rivers,with Xiang River in 1996,Zi River in 1973-1974,Yuan River in 1997-1998 and Li River in 1998,and the time of abrupt beyond 95% confidence interval was 1999,1963,1988,2001 in Xiang River,Zi River,Yuan River and Li River,respectively.Double mass analysis between annual runoff and annual sediment discharge showed that Xiang River had one turning point in 1991,Zi River three points in 1961,1981 and 1997,Yuan River two points in 1979 and 1997,Li River one point in 1996.Turning points of annual sediment discharge in Four Rivers were closely related to the construction of large-scale reservoirs.The reduction of annual runoff,increase of vegetation cover and construction of medium-and large-scale reservoirs were the main reasons accounting for the great reduction of annual sediment discharges of Four Rivers after 2001.