Long-term trend and change point analysis on runoff and sediment fluxes into the sea from the Yellow River during the period of 1950-2007

This paper addressed long-term change characteristics of runoff and sediment fluxes into the sea from the Yellow River based on runoff and sediment load observed at Lijin hydrological station from 1950 to 2007.The Mann-Kendall statistic test was used to estimate the significance of long-term trends in the runoff and sediment time series,and the change point of runoff and sediment time series was determined by the nonparametric Mann-Whitney-Pittitt test and the Bayesian analysis approach.The results show that annual runoff and sediment fluxes change negatively over time at rates of-0.8114 billion m~3/a and-0.0223 billion t/a,respectively.Trend lines have steeper slope during flood season than low water season,especially for the sediment flux.Different significant change points are detected in the runoff and sediment time series.The change points of runoff occurred in 1968,1985 and 2002,and those of sediment flux in 1968,1985 and 1996.The negative long-term change trend and the occurrence of change points are highly associated to natural variation and human activities in the Yellow River basin.The occurrence time of some change points accords even with man-made events.