Analyzing the Relationship between El-Niño Southern Oscillation and Streamflow in Ontario and Quebec Using Wavelet Transforms

Abstract

Abstract. The impacts of El NiA±o Southern Oscillation (ENSO) on streamflow variability have been studied extensively in many different parts of the world. Due to the non-stationary nature of streamflow data, wavelet transform approaches are useful for analyzing these types of data. In the Canadian context, applying the wavelet transform approaches, especially those that involve the use of continuous wavelet transform (CWT) and wavelet coherence (WTC) to analyze the influence of ENSO on streamflow variability, is still rare. This present study assessed the influence of ENSO activity on streamflow in Ontario and Quebec. Monthly data from a total of 8 stations were used. Spearman correlation was used to determine the amount of time taken by streamflow to respond to ENSO activity. The wavelet spectra of streamflow CWT revealed significant periodicities at the 6-month and 12-month wavebands throughout the period covered by the data – this observation is consistent from one station to another. The CWT spectra of the SST data showed significant regions of up to 8 years, most of which occur after 1960. The influence of ENSO on streamflow as seen in the WTC spectra occur both up to and over 8 years. Areas of significant regions observed for periodicities of over 8 years mostly occur after 1960. Spearman correlation analyses indicate that the influence of ENSO is significant for all stations except for Sydenham River. Correlations between SST and reconstructed streamflow data also indicate that the influence of ENSO occurs both at low and high time scales.