近55年来黄河下游泥沙通量的时空变化分析

利用近55a黄河下游输沙率数据,分析泥沙通量在下游的时空变化,得出在不同的时间尺度下各河段泥沙通量的变化速度,孙口以上和艾山-洛口段变化较大.通过非参数Mann-Kendall检验等方法,发现下游年、汛期、非汛期以及多数月泥沙通量显著性减小,其它月份部分站点也有减小趋势.利用有序聚类法得出各站年泥沙通量序列的一级跳跃发生在1979～1986年间,二级跳跃分别发生在1968年、1996年、1999年.利用小波变换的方法,得出年泥沙通量序列具有2～4a的周期,部分时段有8～12a周期,部分河段有17～21a的周期.泥沙通量序列的趋势、跳跃和周期变化与降雨、水土保持、水库拦蓄等因素有关.

Temporal-spatial Changes of the Sediment Flux in the Lower Yellow River during the Past 55 Years

Based on records of sediment discharge during the period of 1950~2005,the temporal-spatial changes of sediment flux through the lower Yellow River has been studied on temporal scales of year,season,and month.Non-parameter Mann-Kendall test,order clustering and wavelet transform methods were used to analyze the sediment flux series’ structure.The sediment flux shows a higher gradient in the reaches upstream Sunkou and Aishan-Luokou.The yearly,flood and non-flood seasonal sediment flux series indicate a rapid decreasing trend in most of months.The yearly sediment flux series experienced the first-level jumps from 1979 to 1986 and the second-level jumps in 1968,1996 and 1999,which have periodicities of 2～4 a,8～12 a,and 17～21 a.Further analyses suggest that the tendency,jumps,and periodicities of the sediment flux have been closely related with changes in precipitation,soil and water conservation practices on the Loess Plateau which is the principal sediment source of the Yellow River,and dams on the main stream.