Wildfires Threaten Water Quality for up to Eight Years After They Burn, Study Shows

Scientists sound alarm over dangerous long-term impacts of wildfires

Wildfires can pollute rivers and streams for nearly a decade after they burn

Residents still trying to rebuild after 2021 White Rock Lake wildfire

In July, four years will have passed since the White Rock Lake Wildfire swept through communities.

Wildfires threaten water quality for up to eight years after they burn

Wildfires don’t just leave behind scorched earth—they leave a toxic legacy in Western rivers that can linger for nearly a decade. A sweeping new study analyzed over 100,000 water samples from more than 500 U.S. watersheds and revealed that contaminants like nitrogen, phosphorus, organic carbon, and sediment remain elevated for up to eight years after a blaze.

Wildfires contaminate water quality for nearly a decade after the blaze

The results showed contaminants like organic carbon, phosphorus, nitrogen, and sediment can degrade water quality for up to eight years after a fire.

Wildfires drive multi-year water quality degradation over the western United States

Wildfires can dramatically alter water quality, resulting in severe implications for human and freshwater systems. However, regional-scale assessments of these impacts are often limited by data scarcity. Here, we unify observations from 1984–2021 in 245 burned watersheds across the western United States, comparing post-fire signals to baseline levels from 293 unburned basins. Organic carbon and phosphorus exhibit significantly elevated levels (p 

Wildfires threaten water quality for up to eight years after they burn, study shows

Years after wildfires burn forests and watersheds, the contaminants left behind continue to poison rivers and streams across the Western U.S.—much longer than scientists estimated.