Changes in High and Low Flow Cycles of the Upper Reaches of Yellow River and Their Circumfluence Backdrop
The changing characteristics of high and low flows of the runoff in the upper reaches of Yellow River and the circumfluence backdrop corresponding with the typical high and low flow years were analyzed according to some relational hydrologic and meteorological data, aimed at searching the weather factors that control the flood discharge in flood season, at affording warranty to the long-term and super long-term forecasts of flood discharge rate, and at programming the use of water resources in the upper reaches of Yellow River. It is revealed that cycles of high and low flows in the upper reaches of the river alternately occur, but the time of the high flow is less than that of low flow on the whole, and the period of an integrated high and low flow cycle is about 18 years in the upper reaches. There is a close relation between the high or low flow of the reaches and the abnormity of circumfluence. The subtropical high over the west Pacific extending to west and the westerly trough occurring in the mid and west of the Tibetan Plateau are the two important factors that bring abundant precipitation and more runoff in flood season of the upper reaches. Thus, the flood discharge rate in flood season of the reaches can be forecasted approximately based on the relations between the high or low flow and the abnormity of circumfluence and the characteristics of prophase circumfluence.
upper reaches of Yellow Riverhigh flow and low flow cyclescircumfluence backdropsubtropical high over west pacificwesterly trough