Analysis on the Change of Stream Flow and Silt Load in the Upper Reaches of the Yellow River since Recent 43 Years

Based on the statistical results of the data of stream flow and silt load measured at Toudaoguai Hydrological Station during the period from 1960 to 2002,in this paper the wavelet analysis theory is applied to study the change trends of annual and seasonal runoff volumes and silt transport quantities in the upper reaches of the Yellow River.The results are mainly as follows:(1) The proportions of inflow and the silt load from the upper reaches of the Yellow River are decreased in flood season but increased in non-flood season.Temporally,the annual runoff volume and the annual silt transport quantity are decreased year by year. The correlativity between the discharge and the silt load is changed to some extent;(2) There are the similar multiple temporal-scale changes of stream flow and silt load.For the same temporal scale,the change of stream flow is different from that of silt transport;(3) The change trend of the annual runoff volume is similar to that of annual silt transport quantity,and both of them are in an obvious decrease trend since the 1980s,but their change trends in non-flood reason are quite different.