Bigger Wildfires Are Threatening America’s Drinking Water for Years After the Flames Go Out
Bigger and more frequent wildfires are contaminating the rivers and streams that supply drinking water to much of the United States, and new research shows the damage can linger for more than a decade after the flames go out.
So far in 2026, there have been 68,179 wildfires across the country, burning more than 14,062 square miles — over 9.5 million acres. After a fire sweeps through hillsides and forests, rains carry ash and organic matter into the streams that feed water treatment plants for towns and cities alike. Communities are working to adapt, but it can take years and require stopgap solutions.
A town that lost its water for months
People in the city of Las Vegas, New Mexico, went without water for months after the Hermit’s Peak/Calf Canyon wildfire contaminated the Gallinas River in 2022. In the four years since, they have had to give residents bottled water and ship tanks in from nearby towns while they collected funds to build a new treatment plant.
Karen Pettine, who has owned the Hillcrest Restaurant for 50 years, said the water crisis forced the restaurant to close, sometimes for a week at a time. “It’s hard to run a restaurant without good water,” she said. “They brought in semi-truckloads of bottled water. You could pick up four cases at a time. The water situation is ongoing because when it rains, it floods and it brings dirty water down the stream.”
Las Vegas Mayor David Romero said climate change has made the things that used to be reliable less predictable.
“It’s a scary situation that we’re all going to encounter,” he said.
Why burned watersheds are so vulnerable
Wildfires are a natural part of forest ecosystems, but an increase in their severity has made the areas that capture, filter and regulate the flow of water — known as watersheds — vulnerable, said Amanda Hohner, an assistant professor at Montana State University who specializes in wildfires and water quality.
Forested watersheds provide water to nearly two-thirds of municipalities in the U.S., according to Carli Brucker, lead author of a University of Colorado Boulder study that assessed wildfire-affected water quality in hundreds of burned basins and compared them to unburned areas. Their study found that the impacts can last up to eight years. A separate U.S. Forest Service research paper found that nitrogen and dissolved organic carbon remained elevated for 15 years following a high-severity fire.
Garrett McKay, an associate professor of civil and environmental engineering at Texas A&M, said utilities are extremely concerned about the impacts wildfires have on water. They are reaching out to experts like him for help finding different water sources or learning how to treat the organic matter coming into their plants.
Water treatment facilities that rely on streams and rivers typically treat high-quality water, aided by trees and soil that act as a natural filtration system, Brucker said. But wildfires cause spikes in heavy metals or dissolved organic matter, which the plants are not built to handle.
That can force treatment facilities to shut off the incoming water and resort to other sources, which may not be immediately available, Brucker said. Some have groundwater or reservoir backups, but even those can be impacted.
The hidden chemistry of post-fire water
Reservoirs can serve as a “sedimentation basin” where particles can settle, said Kyle Shimabuku, an associate professor of civil engineering at Gonzaga University. But sediments from burned vegetation are rich in nutrients, like nitrogen and phosphorus, and as they sit in still water, algal blooms can grow, he said. The algae can make people sick and kill the fish.
Chlorine, routinely used to treat water, is also affected by wildfires, said McKay at Texas A&M. When facilities add disinfectants like chlorine to water, they react with the dissolved organic matter left behind by the fires to form “disinfection byproducts,” which are regulated by the U.S. Environmental Protection Agency because they can cause illnesses, including cancer.
Since plants cannot remove the disinfection byproducts, they must get rid of the organic matter before disinfecting the water, which can cause delays in the water supply.
Fixing the damage costs millions
When a 2020 wildfire burned the area around No Name and Grizzly creeks, the primary water sources for Glenwood Springs, Colorado, officials scrambled to protect against sediment expected to wash down the slopes when spring rains arrived. Within two months, the Colorado Water Conservation Board authorized an emergency loan of $8 million for improvements to the treatment system.
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Fort Collins faced a similar challenge that year when ash and sediment from the Cameron Peak fire forced the city to close its river intake and pull water from the Horsetooth Reservoir, fed by a different watershed.
Las Vegas, New Mexico, was hit harder when the Hermit’s Peak/Calf Canyon fire damaged the Gallinas River watershed in 2022. A massive rainstorm swept ash and sludge from the burn scar into the river and reservoirs, forcing the town to shut down its water treatment plant while it installed additional filters and looked for additional water sources. A massive flood in 2024 carried more burn debris into the town’s two reservoirs, leaving it with only a few days of safe water, and the town hired trucks to bring 2.2 million gallons of water from the nearby towns of Santa Fe and Santa Rosa.
It was hit again in February 2025, when burn scar debris, bad weather and equipment failure caused a pressure drop that resulted in a monthlong boil-water advisory and more water shipments.
“The February event was probably the scariest,” Romero said.
Ultimately, the state and federal governments allocated $148 million to rebuild the town’s treatment plant and help support its efforts to find other options, including drilling wells and reusing water. Groundbreaking on the first phase of the new water treatment plant is slated for Nov. 18, the mayor said.
“We’ve been doing a lot of work for other sources of water and we know with climate change and what we experienced in the past, the Gallinas River is something we can’t depend on forever.”
Why this matters
The findings are especially concerning because climate change and increasingly strong El Niño weather events, which intensify drought conditions, have led to bigger and more frequent wildfires in the U.S. The threat does not end when a fire is put out: it arrives with the first rains after the burn, and it can return with every storm for years.
Water systems are under strain elsewhere too: winter flooding in Gaza has left health officials warning of surging respiratory illness, and natural disasters such as the Mayon volcano’s new lava dome have kept a Philippine province on alert this week. But the wildfire threat strikes the water supplies of American towns directly — and the research now shows the damage is measured in years, not weeks.
Frequently asked questions
How long can wildfire contamination affect drinking water?
A University of Colorado Boulder study of hundreds of burned basins found water-quality impacts can last up to eight years. A U.S. Forest Service research paper found nitrogen and dissolved organic carbon remained elevated for 15 years after a high-severity fire. The Associated Press reports that new studies show contamination can remain for more than a decade.
Why can’t water treatment plants just filter out the ash and sediment?
Most plants are built to treat high-quality water, with trees and soil acting as a natural filter. Wildfires cause spikes in heavy metals and dissolved organic matter that the plants are not designed to handle. Adding chlorine to that water creates disinfection byproducts the EPA regulates because they can cause illness, including cancer — so plants must remove the organic matter before disinfecting, which can delay the water supply.
What happened to the water supply in Las Vegas, New Mexico?
The 2022 Hermit’s Peak/Calf Canyon wildfire contaminated the Gallinas River, leaving the city without water for months. Residents relied on bottled water and trucked-in supplies. A 2024 flood and a February 2025 pressure failure caused further shortages and a monthlong boil-water advisory. The state and federal governments have allocated $148 million to rebuild the treatment plant, with groundbreaking scheduled for Nov. 18.
What to watch next
Las Vegas, New Mexico, breaks ground on the first phase of its new water treatment plant on Nov. 18 — four years after the fire that wrecked its water supply. Researchers are also tracking how this year’s record fire season will affect watersheds in the months ahead, as winter rains wash ash and sediment into the rivers that supply drinking water to towns across the West.
Sources: Associated Press (via KCAU9), The Weather Channel, TIPP Insights, Climate Cosmos.
