Getting dry high and low
Changes in snowpacks were most evident in mid-elevation regions of the Rockies. Snow depth loss emerged as the main driver of SWA decreases in these areas.
The Okanagan-Similkameen drainage region in the British Columbia interior, the Assiniboine-Red River in Saskatchewan and Manitoba, and the vast Saskatchewan River basin which runs from the Rockies across the Prairies to Lake Winnipeg and beyond were the most affected.
The compact, densely populated Okanagan-Similkameen region is heavily reliant on mountain snowpack melt to meet its water needs. Snow storage in the area was shown to have dropped drastically over the two-decade study period.
Meanwhile, the Assiniboine-Red and Saskatchewan River basins show the cumulative effect of small drops in snow cover across large land areas. The researchers say these findings reveal how seemingly insignificant SWA losses can eventually have serious consequences.
More snow in north, less water in south
Unlike traditional methods for measuring water stored in the snowpack, SWA captures rapid changes in snow cover at the beginning and end of the snow season. By analyzing snow depth, density and cover on 25 by 25 km2 grids roughly 18,000 of them, covering 4.5 million km2 the researchers captured regional subtleties such as slopes, terrain types and uneven snow cover distribution in annual, seasonal and monthly time scales.
Nazemi points out that despite popular belief, total SWA across Canada has actually increased, particularly in northern regions and near to the Arctic coast. Warmer temperatures have caused Arctic Ocean ice to recede, releasing more moisture into the atmosphere. That moisture can fall as snow in cooler inland areas, but it does not necessarily contribute to the hydrological cycle that supports Canadian populations and socio-economic activities.
“The asymmetric effect of this drought in which a three per cent significant drop in SWA can impact 26 per cent of the land containing 86 per cent of the population shows that this requires a re-evaluation of our water management system,” Nazemi says.
Robert Sarpong, MASc 2025, and Amir AghaKouchak of the University of California, Irvine, contributed to this study.
This research received funding from Canada’s New Frontier Research Fund Exploration and the Natural Science and Engineering Council Discovery grant program.
Read the cited paper: “Creeping snow drought threatens Canada’s water supply“