Impacts of Large-Scale Circulation Variability on Low Streamflows over Canada: A Review

Abstract

Low streamflows constitute an important component of hydro-climatic extremes. This is particularly true for Canada where reduced flows can affect several economic and environmental activities ranging from less hydro-electric production and increased freshwater transportation costs, to reduced water quality and ecological habitat destruction. This paper reviews past research regarding the impacts of large-scale circulation patterns on streamflow variability (including low flows) over Canada. Results from the various studies reveal that streamflow responses are generally consistent with those observed for large-scale climate. For western Canada, this includes a higher frequency of low-flow events in association with the warmer/drier conditions during El Niño events and positive phases of the Pacific Decadal Oscillation (PDO) and the Pacific North American (PNA) pattern. Relationships in northern/northeastern regions of the country are less robust but in general, reduced streamflows occur during positive phases of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). However, it is clearly evident that the spatial and temporal aspects of these relationships are greatly influenced by hydro-climatic complexities associated with individual watersheds, especially in the cordilleran areas of Canada. Future research requires more in-depth analyses into the spatial and temporal aspects of relationships between circulation variability and low-flow occurrences over critical watersheds within Canada including the combination of climatic patterns and associations with regional, synoptic-scale circulation. The incorporation of fully coupled climate and hydrologic models to assess the impacts of projected climate change on future low-flow occurrences is also needed. This research would result in a better understanding and enhanced prediction of low streamflow events that is critical for the current and future efficient management of water resources throughout the country.