[1] Changes in air temperature, precipitation, and, in some cases, glacial runoff affect the timing of river flow in watersheds of western Canada. We present a method to detect streamflow phase shifts in pluvial, nival, and glacial rivers. The Kendall-Theil robust lines yield monotonic trends in normalized sequent 5-day means of runoff in nine river basins of western Canada over the period . In comparison to trends in the timing of the date of annual peak flow and the center of volume, two other less robust metrics often used to infer streamflow timing changes, our approach reveals more detailed structure on the nature of these changes. For instance, our trend analyses reveal extension of the warm hydrological season in nival and glacial rivers of western Canada. This feature is marked by an earlier onset of the spring melt, decreases in summer streamflow, and a delay in the onset of enhanced autumn flows. Our method provides information on streamflow timing changes throughout the entire hydrological year, enhancing results from previous methods to assess climate change impacts on the hydrological cycle.

Trends and variability in the 1964–2007 annual streamflow for 45 rivers spanning 5.2 × 106 km2 of northern Canada are investigated. Discharge averages 1153 km3 yr−1 with a standard deviation of 71.4 km3 yr−1 and coefficient of variation (CVQ) of 6.2% over the 44‐year period. A trend analysis reveals a recent (1989–2007) 15.5% increase in the annual flows owing to much‐above average values recorded over the past decade. Trends in CVQ computed from 11‐year moving windows of annual streamflows exhibit spatially coherent signals with increasing variability across most of northern Canada, excluding some rivers with outlets to the Labrador Sea and eastern James Bay. For the period of interest, 46% and 30% of the available gauged area and river discharge, respectively, experienced detectable increases in variability. This provides observational evidence of an intensifying hydrological cycle in northern Canada, consistent with other regions of the pan‐Arctic domain.

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