Variations in the key hydrological elements of the Yarlung Zangbo River basin

Based on the monthly water level, runoff, precipitation and evaporation data from the four main hydrometric stations in the middle section of the Yarlung Zangbo River basin from 1956 to 2000, the periodic oscillations, trends and transformation characteristics at different time-scales are investigated via wavelet analysis. Moreover, the main periods of each time-series are identified by estimating the wavelet variance. The results show that the transformation scales of the monthly variation of the key hydrological elements over the last 44 years were 80-120,40-70 and 16-24 months and that a high level of consistency was maintained at 16-24 months, where the periodic oscillation was the most significant. In addition, the first and second main periods of all hydrological elements were 18 and 9 months, respectively.