Analysis on the Process of Flow-Sediment in Jianli Reach of Yangtze River before and after the Construction of Three Gorges Project

摘要

Jianli Reach has long been exposed to labile main flow and the frequent translocation between the main channel and the lateral branch. To investigate how the long-term process of flow-sediment influences the adjustment of river channel pattern, monthly time series (1951-2009) of runoff and sediment load at Jianli hydrological station of Yangtze River were analyzed using three methods: R/S analysis to estimate Hurst exponent, Mann-Kendall method and the time series anomaly analysis. The result shows that on 1 year time scale, the values of Hurst exponent are indicating persistence, that is to say, the trend of runoff and sediment in the future will generally be the same as the past, and the persistence in runoff series is stronger than that in the sediment load. The period of oscillation in annual runoff and in sediment load is about 30 years. The result of Mann-Kendall test shows an abrupt change point of runoff time-series at 1967 and an abrupt change point of sediment load time-series at 2003. And during the flood season, the values of Hurst exponent still indicate persistence, which is weaker than that in whole year correspondingly.