Multple time scales analysis and cause of runoff changes of the upper and middle reaches of the Yellow River
黄河上中游天然径流多时间尺度变化及动因分析

Because of the influence of climate change and human activities,runoff change has oc-curred.This paper analyzes the natural runoff series of the upper and middle reaches of the Yel-low River with the theory of wavelet transformation,reveals multi-time scale changes rule of runoff,and discusses the influencing factors of runoff multi-time scale changes.The results showed that climatic conditions such as precipitation mainly controlled river runoff variations.But varia-tions in drainage basin underlying surface and local climate factor brought by human activity af-fected natural annual runoff.The results are important to know runoff changes and to exploit wa-ter resources of the upper and middle reaches of the Yellow River.