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It is well known that the spatial and temporal patterns in streamflow can be correlated with many teleconnections, e.g., solar activity and climatic phenomena such as El Niño. However, fewer studies have attempted to analyze both the influence of solar activity and large scale climatic phenomena on natural processes, particularly hydrological processes. In this study we examine long term records of solar activity and El Niño for their combined influence on streamflow across southern Canada. Data used in the analysis include sunspot number, sea surface temperature anomaly in Niño region 3.4, and annual mean streamflow from 50 Canadian Reference Hydrometric Basin Network (RHBN) stations with record lengths ≥50 years (14 of them ≥90 years). Analysis is performed using Fourier spectrum analysis (FSA), continuous wavelet transform (CWT), and cross wavelet transform coherence analysis (WTC). Results of FSA show that for almost all the 14 RHBN stations with record lengths of ≥90 years, streamflow exhibits periodicities of approximately 11 and 22 years (which is in accordance with solar activity), as well as shorter term periodicities consistent with El Niño (2–7 years). WTC analysis confirms the correlation between these periodicities (2–7 years, 11 years, 22 years) in streamflow with solar activity and El Niño records. Both solar activity and El Niño's influences on annual mean streamflow in 18–32 year bands are common, while the influence of El Nino is more extensive in the 2–7 and ∼11 year bands. Through examination of correlations between solar activity and streamflow, El Niño and streamflow, and finally El Niño and solar activity, WTC analysis has identified that solar activity affects El Niño first, and this influence is then transferred by El Niño to streamflow. This study expands on earlier efforts examining linkages between El Niño and streamflow across southern Canada to an examination of linkages between solar activity, El Niño, and streamflow.

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