长江中下游许多汊道河段主支汊易位频繁,但对产生这一现象的主要驱动机理与影响因素一直争议不休。研究采用距平分析法、Mann-Kendall分析与基于分形理论的极差分析法相结合的方式,详细分析了监利河段1951年-2009年间流量和输沙率时间序列年尺度的变化过程。结果表明,流量及输沙率的Hurst数分别为0.943 0和0.923 9,均十分接近1.0,具有很强的持续性。Mann-Kendall分析发现,输沙率序列无明显突变,流量序列仅在1967年出现突变,主要由上游实施裁弯工程所致。系统分析来水来沙的匹配关系发现,该河段主支汊易位时间与水沙序列匹配状态有明显的相关关系,在＂水多沙少＂时期,监利右汊为主汊;而在＂沙多水少＂时期,监利左汊为主汊。
Many anabranching reaches in the middle and lower reaches of Yangtze River frequently switch the main flow from one channel to another.The mechanism and influencing factors of the phenomenon are still elusive.To examine how the phenomenon is related to the changes in hydrological process,this study applied rescaled range analysis,Mann-Kendall test,and anomaly analysis methods and examined in detail the changes in the time series of annual flow discharge and annual sediment transport rate based on observations from 1951 to 2009at Jianli hydrological station in the Middle Yangtze River.It was shown that the Hurst exponents of the time series of flow discharge and sediment transport rate were respectively 0.9430 and 0.9239,implying that both time series had very strong persistence.The Man-Kendall test showed that a significant abrupt change occurred to the flow discharge time series in 1967,mainly resulting from a river cutoff project taking place upstream;and there was no significant abrupt change in sediment transport rate time series during the same period.An obvious correlation was found between the time of main channel switches in this reach and the matching relation between flow and sediment series.When there was abundant flow discharge and inadequate sediment,the right channel was the main channel;when there was abundant sediment and inadequate flow discharge,the left channel was the main channel.
South-to-North Water Transfers and Water Science ＆ Technology
main channel switch
sediment transport rate