本文采用Morlet小波对1956~2000年雅鲁藏布江流域6个站点的径流序列进行了分析,揭示了不同时间尺度下四个季节以及年平均径流量的丰枯交替特性、突变性和周期性,通过小波方差确定各序列存在的主要周期。结果表明:在15年时间尺度上,雅江流域四个季节的径流变化趋势基本一致;发生突变的年份主要在1957、1967、1976、1983、1992年;径流序列第一主周期主要以15年长周期和2年短周期为主,第二主周期以15、6、2~3年的长、中、短周期为主;秋季和冬季径流序列的周期空间分布基本一致,年平均径流序列的周期分布与夏季最为接近;除拉萨河子流域春季在2~3年尺度上处于枯水期外,其他子流域其他时段在任何时间尺度上未来几年里都将处于丰水期。

In order to analyze the spatial structure and multi-scale characteristics of runoff time series in the Yarlung Tsangpo Zanggo River basin, the monthly runoff data at 6 meteorological stations in the study area from 1956 to 2000 are investigated. The periodic oscillation of runoff variation and the points of abrupt change at different time scales are investigated by using wavelet method in this study. At the same time, the main periods of each time series are identified by estimating wavelet variance, which is helpful to determine the spatial distributions of periodicity. Application of the Morlet wavelet function for the runoff time series has shown that the seasonal and annual trends of runoff change in the last 44 years were consistent at the scale of 15 years, and the abrupt change occurred mostly in 1957, 1967, 1976, 1983 and 1992. There are more points of abrupt and more numbers of alternation between low flow and ample flow at the smaller scales. There is an obvious periodic oscillation of 15 and 2 years for the first main periods for the seasonal and annual runoff variation, and 15, 6 and 2~3 years for the second main periods. The spatial distributions of periodicity for autumn and annual runoff time series are similar to some degree with those of winter and summer runoff, respectively. Both seasonal and annual runoff at any scales in the Yarlung Zangbo River basin will increase in the near future except the spring runoff in the Lhasa River basin at the scale of 2~3 years. The characteristics of runoff time series such as long-term trends, points of abrupt and periodic oscillation are consistent well with those of precipitation time series in the study area. It has been shown that the runoff recharge is mainly from precipitation in the Yarlung Zangbo River basin.