Abstract: The runoff time series during 1956-2012 in the source region of Three Rivers (the Yangtze River, the Yellow River, and the Lancang River) are analyzed by using linear regression, moving average, Mann-Kendall test, accumulative anomaly, moving t test and Morlet wavelet analysis method. Results indicate that: 1)during the past 57 years, the annual runoff at Zhimenda station, Jimai station and Xiangda station presented upward trend, among which the runoff trend at Zhimenda station was significant, whereas at Tangnaihai station the annual runoff presented a downward trend; 2) abrupt change occurred in 2004 at Zhimenda station and Jimai station rather than the other stations; 3)annual runoff in the source region of Three Rivers had main oscillation cycles in common of 6-8 years and 23 years, of which the interval of 23 years experienced the most significant fluctuation. There were three more-than-normal periods and two less-than-normal periods. The research results provide reference for the protection and management of water resources in the middle and lower reaches.

Key words: Source Region of Three Rivers, runoff variation, Mann-Kendall test, Morlet wavelet analysis, accumulative anomaly, moving t test