Intraannual variation of runoff in the Chengbi River Basin

Eight intraannual indexes of runoff,including non-uniform adjustment coefficient and concentration ratio,were calculated for Bashou and Pingtang stations during 1963-2014 in the Chengbi River Basin.,The trend of annual runoff was detected with linear regression,Mann-Kendall trend test and R/S analysis.The results show that the intraannual runoff distribution is highly uneven in the past 52 years and varies with time in the Chengbi River Basin.The inhomogeneity of runoff distribution is increasing,and all other indices decrease.The concentration period is mainly in July,and Lorenz asymmetry coefficient shows that the main cause of uneven annual runoff distribution is the months with larger runoff.The Hurst values of eight indices are all greater than 0.5,which can be used to predict the annual distribution of runoff in the Chengbi River Basin.A positive continuity is consistent with the overall trend of the past.The intraannual distribution of runoff became lower and lower as time goes,which gradually transform from non-uniformity to homogeneity processes in the Chengbi River Basin.

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