关键词: 径流变化; 周期分析; 气候变化; 极点对称模态分解; 长江; 黄河; 澜沧江;

Abstract: Climate change and the strengthening of human activities have influenced the earth's water cycle system.Therefore, it is of great significance to re-understand and master the evolution of water cycle in the basin.We use the extreme-point symmetric mode decomposition(ESMD) method to analyze the runoff variation in the Three-River Headwaters Region from aspects of trend, sudden change, and cycle, and compare the ESMD with existing detection methods.The results showed that:(1) in the source region of the Yellow River, the increasing trend of precipitation was not obvious and the evapotranspiration increased as the temperature increased, which resulted in an insignificant downward trend of annual runoff.The annual runoff in the source region of the Changjiang River and the Lancang River increased significantly due to the increase of precipitation and glacial snow melting.(2) The 61 years runoff process of the Yellow River source region experienced significantly abrupt changes between 1990～1994 and around 2008.The runoff process of the Changjiang River source region experienced significantly abrupt change around 2006.The runoff process of the Lancang River source region had an abrupt changes in the 1990 s and around 2008.The 61-years runoff process of the Yellow River source region had cyclic variation of 12～15 a and 30 a.The 60-years runoff process of the Changjiang River source region had 13～15 a cyclic variation.The 49-years runoff process of the Lancang River source region had cyclical changes of 15～16 a and 28 a.And these cyclical changes dominate the characteristics of the annual runoff variation of the Three-River Headwaters Region.

Key words: runoff variation; cycle analysis; climate change; ESMD; Changjiang River; Yellow River; Lancang River;