River basin, China

ABSTRACT: Daily precipitation data of 148 weather stations located in the Yangtze River basin (P.R. China) are analysed to detect cycles in the annual frequency of occurrence of precipitation events of 1-, 5- and 10 days duration. These events were defined in terms of exceedances of some selected thresholds. The events corresponding to 10, 25 and 30 mm thresholds for 1-, 5- and 10-day precipitation totals, respectively, are analysed in detail. For the identification of cycles, basin-wide averaged standardized time series of frequency of precipitation events are used. It is found that peaks in the smoothed time series occurred around 1974, 1982 and 1991. The Fourier, autoregressive and wavelet analyses reveal distinct cycles of 7–9 and 2–3 year periods, which dominate large parts of the time series. In addition, a shift towards a 4–5 year period in the annual frequency of precipitation events is noticed since the mid- to late-nineties. Major peaks in the annua