Study on the variation characteristics of annual rainfall and runoff in Oujiang River Basin of Zhejiang Province

Abstract

In this paper, Mann-Kendall method and wavelet analysis method are used to analyze the annual rainfall and runoff data in Oujiang River Basin of Zhejiang Province, and the following conclusions are obtained: in the past 50 years, the annual average rainfall series increase and the annual runoff series decrease in Oujiang River Basin. The reason for this is that in 1960s, many hydraulic structures were built near Xuren station, such as river dams, which led to the rapid decline of runoff in the flood season. The results of Morlet wavelet analysis show that there is significant multi-time scale variation characteristic in the annual average rainfall and runoff series. The periodicity of the annual rainfall series exhibits three types of variation trends for different time-scales, i.e. 22-to 30-year scale, 10-to 22-year scale, and 3-to 10-year scale. While the periodicity of the annual runoff time series exhibits three types of variation trends for different time-scales, i.e. 15-to 25-year scale, 8-to 15-year scale, and 3-to 8-year scale.