Creeping snow drought threatens Canada’s water supply

Snow water is key to water supply in cold regions and beyond. Here we introduce Snow Water Availability that quantifies water stored in the snow-covered portion of an area. By integrating a plausible set of available gridded datasets for snow depth, density, and cover fraction, we form four estimates of Snow Water Availability at the 25 × 25 km2 across Canada and Alaska. We show that annual long-term mean of Snow Water Availability over the domain was 996 ± 170 km³ during 2000–2019. While annual Snow Water Availability increased from 799 ± 121 km³ in 2000-2009 to 1208 ± 231 km³ in 2010-2019, significant losses (p-value ≤ 0.05) were observed in ~3% of the domain, mainly in North American Cordillera, headwaters to major rivers in western Canada. These losses alongside insignificant decreases across southern Canada can threaten water supply in a quarter of the country, where ~86% of its population reside. While 2000-2019 Snow Water Availability increased, nearly 3% of Canada and Alaska, particularly in the North American Cordillera, underwent significant losses. Along with other insignificant losses, water supply for 86% of Canadians is threatened.