Bigger and more frequent wildfires are threatening drinking water supplies across the United States, and new research shows the contamination they leave behind can last for years — in some cases more than a decade, the Associated Press reported on November 13. Wildfires leave charred trees and scorched vegetation on hillsides, and when rain comes, it carries ash and organic matter into the streams and rivers that supply water treatment plants for towns and cities alike.

The scale of the fire problem is growing. So far in 2026, there have been 68,179 blazes in the United States burning more than 9.5 million acres (3.8 million hectares), according to figures cited by the AP. Researchers say climate change and increasingly strong El Niño weather events, which intensify drought conditions, have led to bigger and more frequent fires — and each major fire can damage the watershed its community depends on long after the flames are out.

The New Mexico town still living the crisis

The clearest example is Las Vegas, New Mexico, where residents went without reliable water for months after the Hermit's Peak/Calf Canyon wildfire contaminated the Gallinas River in 2022. In the four years since, the town has had to give residents bottled water and ship tanks of water in from nearby towns while collecting funds to build a new treatment plant. A massive rainstorm swept ash and sludge from the burn scar into the river and reservoirs, forcing the town to shut down its treatment plant while it installed additional filters and looked for other water sources.

The crisis kept returning. A massive flood in 2024 carried more burn debris into the town's two reservoirs, leaving residents with only a few days of safe water; the town hired trucks to bring in 2.2 million gallons (8.3 million litres) of water from Santa Fe and Santa Rosa. In February 2025, burn-scar debris, bad weather and equipment failure caused a pressure drop that brought a month-long boil-water advisory and more emergency water shipments. Las Vegas Mayor David Romero called the February event 'probably the scariest' and said climate change has made things that used to be reliable less predictable.

For local businesses, the water crisis is an economic one. Karen Pettine, who has owned the Hillcrest Restaurant for 50 years, said the 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. 'We used some paper plates at times. 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.'

How burned landscapes poison the treatment process

Wildfires are a natural part of forest ecosystems, but an increase in their severity has made watersheds — the areas that capture, filter and regulate the flow of water — 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 US, 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 with unburned areas; that study found the impacts can last up to eight years.

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 and dissolved organic matter, which the plants are not built to handle. That can force facilities to shut off incoming water and turn to other sources that may not be immediately available; some have groundwater or reservoir backups, but even those can be affected. Reservoirs can act as a sedimentation basin where particles settle, said Kyle Shimabuku, an associate professor of civil engineering at Gonzaga University, but sediments from burned vegetation are rich in nutrients such as nitrogen and phosphorus, and as they sit in still water, algal blooms can grow — algae that can make people sick and kill fish.

The treatment chemistry itself is part of the problem. Chlorine, routinely used to treat water, reacts with the dissolved organic matter left behind by fires to form 'disinfection byproducts,' said Garrett McKay, an associate professor of civil and environmental engineering at Texas A&M University. Those byproducts are regulated by the US Environmental Protection Agency because they can cause illnesses, including cancer. Because plants cannot remove the byproducts once formed, they must remove the organic matter before disinfecting the water, which can cause delays in supply. McKay said utilities are extremely concerned about wildfire impacts and are reaching out to experts for help finding different water sources or learning how to treat the organic matter coming into their plants.

Colorado's costly scramble — and what happens next

Colorado communities have already paid heavily. When a 2020 wildfire burned the area around No Name and Grizzly creeks, the primary water sources for Glenwood Springs, officials scrambled to protect against sediment expected to wash down 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. That same year, ash and sediment from the Cameron Peak fire forced Fort Collins to close its river intake and pull water from Horsetooth Reservoir, which was safe because it is fed by a different watershed.

For Las Vegas, New Mexico, the state and federal governments ultimately allocated $148 million to rebuild the town's treatment plant and support efforts to find other options, including drilling wells and reusing water. Groundbreaking on the first phase of the new treatment plant is slated for November 18, Mayor Romero 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,' he said. For communities across the fire-prone West — including the Central Valley and foothill towns where many Punjabi-American families and truckers live and work — the studies carry a practical warning: a fire season can become a water problem that lasts for years, and adapting treatment systems can cost facilities millions of dollars.