Earlier Snowmelt Across Western North America Threatens Summer Water Supplies

Nature Communications Earth & Environment, 22 May 2023

The ability of mountain snowpack to store water has significantly decreased across 25% of the Cascades, Rockies, Sierra Nevada and Columbia Mountains over the past seven decades. In coming summers, the Western U.S. and Canada will experience increased risk of wildfires and water shortages, with some regions reliant on late summer meltwater at higher risk than others. This study bridges a gap in hydrology research, creating a new metric – a “snow storage index” – to evaluate how future changes in climate may decrease local and regional water availability based on the timing of snowfall and snowmelt. The relationship between these two factors is crucial; in regions such as the Cascades where snow accumulates during the fall and winter, meltwater is released early in the spring and can disappear entirely before the end of summer, leading to water scarcity. Communities that have grown up and for decades, or even centuries have relied on these frozen water resources will need to find other sources, adapt or relocate. In contrast, the Rocky Mountains experience alternating patterns of snowfall and snowmelt throughout the winter and spring, which should make it somewhat easier for communities to adjust to declining snowpack as temperatures rise. These findings make it clear however that limiting emissions is the best way to preserve these natural water towers, and prevent water scarcity during the warm and dry seasons towards the end of summer into the fall, when demand is the greatest.

https://www.nature.com/articles/s43247-023-00751-3