Hydrologic Characteristics Analysis of Monthly Runoff Series in Lower Yellow River

Taking the 34 years (1970~2003) monthly runoff series and annual runoff series obtained from Lijin station and Huayuankou station as the basic data, the wavelet analysis (WA) method and the self-organized map (SOM) were used to establish a WA-SOM coupling model respectively to comparative analysis variation characteristics of the lower Yellow River´s runoff from the space. It could be seen from the results that: The monthly runoff and the annual runoff decreased significantly of the lower Yellow River, however, coefficient of variation of monthly runoff series and annual runoff series increased remarkably, The main periods of monthly runoff of the lower Yellow River became more complex in the whole, The runoff volume of the lower Yellow River was more concentrated in July, August, September and October, The runoff characteristics of January and February of the lower Yellow River had no much change, but the runoff series of August, September and October became conspicuous different.