Abstract: The runoff change and responses to precipitation in the source regions,-huangheyan, Huangheyan-Jimai, Jimai-Maqu and Maqu-Tangnaihai, of the Yellow River were investigated. The results showed that:The flood season runoff varied annually in the studied area as a whole. The runoff increased in the Jimai station, but decreased in Jimai-tangnaihai. Concentrated period of runoff in all segments came earlier and the trend in the downstream was more obvious than that in the upstream. The flood season precipitation declined with a significant increase, significant increase, decrease, significant increase for the four segments, respectively. The concentration degree of precipitation was higher than that of runoff. The runoff generation capacity of precipitation weakened from the late 1980s to the middle 1990s.The runoff generation capacity of precipitation increased around 2005 compared with the early stage of the analysis period in the middle and upper reaches. While reduced in middle and lower reaches. The relationship between annual runoff and precipitation in different periods were different. Lagging days of concentrated period of runoff relative to precipitation reduced in Maqu, but increased in Maqu-Tangnaihai.

Key words: Yellow River, runoff, precipitation, time lag