Bigger and more-frequent wildfires threaten water supplies across the US

Wildfires in the United States are becoming larger and more frequent, threatening water supplies across the country. New studies reveal that contamination from these fires can persist for over a decade in the streams and rivers that provide drinking water to much of the nation.

These charred trees and scorched vegetation from wildfires impact water quality, and the effects are particularly concerning as climate change and strong El Niño weather events intensify drought conditions, leading to more destructive fires. In 2026 alone, there have been 68,179 wildfires burning more than 9.5 million acres.

After a wildfire, rains carry ash and organic matter into streams, which then flow into water treatment plants serving towns and cities. Communities are adapting, but effective solutions often require years and stopgap measures. Las Vegas, New Mexico, experienced a water crisis after the Hermit's Peak/Calf Canyon wildfire contaminated the Gallinas River in 2022. Residents had to rely on bottled water and even ship in tanks from nearby towns while funds were raised to build a new treatment plant.

The sediment from burned landscapes poses a significant challenge for water-treatment plants. Amanda Hohner, an assistant professor at Montana State University, explains that forests provide water to nearly two-thirds of U.S. municipalities, and wildfires are making watersheds vulnerable.

High-quality water sources, aided by trees and soil acting as natural filters, are threatened by wildfires. The heavy metals and dissolved organic matter in the aftermath can overwhelm treatment facilities, forcing them to shut off the incoming water and resort to alternative sources that may not be immediately available. Reservoirs, which can serve as sedimentation basins, may also be impacted by nutrient-rich sediments from burned vegetation, potentially leading to algal blooms that can make people sick and kill fish.

Chlorine, commonly used to treat water, can also be affected by wildfires, forming harmful disinfection byproducts that pose health risks. Utilities are reaching out to experts for help finding alternative water sources or learning how to treat the organic matter entering their plants. Implementing new options to address these challenges can cost facilities millions of dollars.