• wavelet analysis;
  • Turkey;
  • precipitation;
  • runoff


This study focuses on the variability of precipitation and runoff over time and the relationship between precipitation and runoff at the Aegean region of Turkey. The wavelet transform technique, which has been widely used for the analysis of hydrological data in the last years, provides detailed information regarding time-frequency representation of the data. According to the continuous wavelet transform (CWT), the main periodic events are seen at the scale levels of 1–4 and 16 years. This study shows that variability of both the runoff and the precipitation over time is generally similar, with noticeable decrease in the runoff in all the stations. The dominant inter-decadal periodic events are seen approximately at the 16-year scale level. This periodicity is dominant between 1962 and 1985 for the runoff data. The power of the 16-year periodicity becomes less apparent after 1985. In addition, the global wavelet spectrum (GWS) and the decomposed series of the hydrological data were studied to investigate the effective periodic characteristic of the observed data. In this study, the period of investigation is 39 years extending from 1962 to 2000. The validity of the decreasing trend founded by previous studies for the Aegean hydrological data is verified by the wavelet analysis. Copyright © 2010 Royal Meteorological Society