长江流域近期水沙变化趋势及成因分析

Analysis of Recent Variation Trend and Cause of Runoff and Sediment Load Variations in the Yangtze River Basin

采用双累积曲线法分析了2000—2013年长江流域7大水文站水沙变化关系,基于Mann-kendall检验法和Yamamoto突变检验法研究水沙变化趋势和突变年份。结果表明,屏山、朱沱和寸滩站的双累积曲线较为顺直。宜昌、沙市、汉口和大通站则均在2005年发生转折,斜率减小,输沙量大幅减小;长江干流径流量的变化趋势较为平稳,发生突变的现象少,仅屏山站于2001—2002和2005—2006年发生突变,而输沙量的变化趋势则较为明显,常发生强突变现象,且宜昌、沙市、汉口和大通站均无虚假点出现;造成长江干流2000年以来输沙量显著减小的主要原因是三峡水库的蓄水运用和水土保持工作的持续开展,而降雨量下降是导致径流量减小的因素之一。

The double mass curve method was adopted respectively to analysis the seven hydrological stations＇s relationship between water and sediment in the Yangtze river basin from 2000 to 2013 in this paper. Based on the non-parameter statistical methods of Mann-Kendal test and Yamamoto mutation test, the change trend and mutation years of water and sediment were analyzed. The results showed that the double mass curves of Pingshan, Zhutuo and Cuntan station were more straight. However, all the double mass curve of Yichang, Shashi, Hankou and Datong station had an obvious turning point in 2005. The slope was reduced after the turning point which showed that the sediment load was decreased significantly; The runoff trend of the Yangtze river was relatively stable and the catastrophe phenomenon was less, and only pingshan station had an obvious turning points in 2001-2002 and 2005-2006. However, the changed tendency of annual sediment discharge was more obvious and the catastrophe phenomenon often occured. Besides, no false points were found in Yichang, Shashi, Hankou and Datong station; the the three gorges reservoir and the closure work of Xiluodu and Xiangjiaba hydropower station＇s closure work, coupled with the continuous work of soil and water conservation are the main reasons of sediment-transportation decreasing in the mainstream of the Yangtze since 2000, and the declining rainfall is an important factor that causes the decrease of runoff.