Bigger and more-frequent wildfires threaten water supplies across the U.S.

Wildfires are increasingly damaging US watersheds that supply drinking water to towns and cities, while new research suggests contamination can persist for years after a fire. The findings raise concerns as hotter, drier conditions and stronger El Niño events contribute to larger and more frequent fires.

A University of Colorado Boulder study found water-quality impacts lasting up to eight years across hundreds of burned watersheds; other studies cited in the article suggest contamination may persist for more than a decade. In Las Vegas, New Mexico, the 2022 Hermit's Peak/Calf Canyon fire polluted the Gallinas River, leaving residents reliant on bottled water and temporary supplies while the city raises funds for a new treatment plant. Ash, organic matter and nutrients can overwhelm treatment systems and contribute to algal growth in reservoirs.