关键词: 水沙演变, M-K检验, 小波分析, 荆江三口

Abstract: In order to find out the evolution characteristics of annual runoff and sediment of the three outlets in the Jingjiang River, Mann-Kendall trend, mean difference t-test and wavelet analysis were used in this paper to systematically analyze the long time sequence of annual runoff and sediment of the three outlets (Songzikou, Taipingkou and Ouchikou) in Jingjiang River into the Dongting Lake during 1951-2011. On the basis of identifying the law of runoff and sediment process of the three outlets, this paper probed into the reasons for the variation of the annual runoff and sediment and the influencing mechanism of the Jingjiang River. The result shows: 1) The overall runoff and sediment quantity of the three outlets in Jingjiang River presented a trend of reducing. Annual runoff and sediment evolution process of the three outlets had distinct stages. The shedding sediment of the three outlets into the lake reduced, and the sediment deposition of the Dongting Lake reduced accordingly, which has a positive role to reduce lake sediment deposition. The flow mutation point of the three outlets occurred in the 1960s and the 1970s, and sediment mutation point occurred in the 1950s, since then the runoff and sediment of the three outlets had always shown a significant decreasing trend. 2) M-K trend analysis and average variance t-test indicated in terms of runoff changes: the runoff mutation point of Yichang station occurred in 1969 and 2003; the runoff mutation point of Songzikou occurred in 1969 and 1981; the runoff mutation point of Taipingkou occurred in 1962 and 1976; the runoff mutation point of Ouchikou occurred in 1963 and 1964. As for sediment changes: the sediment discharge fluctuates significantly, and has shown an extremely significant decreasing trend since 1996; the sediment discharge of the three outlets had declined significantly in the past 60 years, and the sediment mutation occurred in the 1950s. In the case of wavelet analysis: the runoff and sediment evolution of the Taipingkou and Ouchikou had the same periodicity, all being 31 years in periodic change. The runoff and sediment changes at Songzikou and Yichang stations have the same cycle respectively, being 16 years and 33 years in periodic change. 3) Human factor has accelerated reducing trend of runoff and sediment of the three outlets of the Jingjiang River, but it is not the root reason for the runoff and sediment evolution mutations.

Key words: wavelet analysis, the three outlets of Jingjiang River, runoff and sediment evolution, Mann-Kendall test