A Comparison of Trends in Hydrological Variables for Two Watersheds in the Mackenzie River Basin

A study of trends and variability of hydrological variables was conducted for natural streamflow gauging stations within two watersheds that are important sources of flow within the Mackenzie River Basin. A comparison was made between trend results for the Liard River Basin and for the Athabasca River Basin. These basins represent a north-south transect of high elevation headwater basins within the Mackenzie River system and are significant since they produce 34% of the annual flow, while occupying only 24% of the total drainage area. Trend analysis was conducted using the Mann-Kendall test with an approach that corrects for serial correlation. The global (or field) significance of the results for each watershed was evaluated using a bootstrap resampling approach. The relationships between trends in hydrological variables and trends in meteorological variables were investigated using partial correlation analysis. The results reveal more trends in some hydrological variables than are expected to occur by chance. In general, both basins exhibit an increase in winter flows and some increase in spring runoff. These increased flows are somewhat offset by decreases (not field significant) in summertime flow. Almost 50% of the stations used in the analysis show an increasing trend in annual minimum flows. Other differences in trend responses are noted for the two watersheds and possible explanations for the differences are hypothesized.