Climatic influences on streamflow timing in the headwaters of the Mackenzie River Basin

The Mann–Kendall non-parametric test for trend is used to explore the trend behaviour of nine measures of the timing of runoff. The relationship between trends in timing measures and trends in meteorological variables are investigated using partial correlation analysis. The relationships between six climate indices and trends in the timing measures are also examined. The analysis is conducted for 26 streamflow gauging stations from three sub-watersheds of the Mackenzie River Basin in northern Canada. The results reveal that for several of the timing measures, many more trends are identified than can be expected to occur by chance. The spring freshet is observed to be occurring earlier with this timing shift appearing particularly strong in headwater catchments. Based on the partial correlation analysis, it is plausible to attribute some of the observed trends to trends in meteorological variables. Timing of runoff is affected by the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO), the North Pacific (NP) index and the Atlantic Multidecadal Oscillation (AMO) but not by the El Niño-Southern Oscillation (ENSO) or the Arctic Oscillation (AO).