City officials scrambled to protect the treatment system, turning to the Colorado Water Conservation Board for help. Within two months, the board authorized an emergency loan of $8 million for upgrades. It was a costly, rapid response to a problem that scientists now say can persist for nearly a decade.

New studies show that wildfires can contaminate drinking water supplies for up to eight years, a finding with urgent implications as climate change and stronger El Niño events intensify drought and drive bigger, more frequent blazes. So far in 2026, 68,179 wildfires have burned more than 14,062 square miles across the United States, according to federal figures.

Forested watersheds supply water to nearly two-thirds of U.S. municipalities, according to Carli Brucker, lead author of a University of Colorado Boulder study that assessed water quality in hundreds of burned basins. Her research found that the impacts can last up to eight years — far longer than many utilities had assumed.

“It’s a scary situation that we’re all going to encounter,” said David Romero, mayor of Las Vegas, New Mexico, a town that has become a case study in the prolonged agony of post-fire water contamination.

In 2022, the Hermit’s Peak/Calf Canyon fire damaged the Gallinas River watershed. A massive rainstorm then swept ash and sludge into the river and reservoirs, forcing the town to shut down its treatment plant. Residents went without water for months. Since then, the community has relied on bottled water shipments and tanks trucked in from nearby towns while collecting funds to build a new treatment plant.

A 2024 flood carried more burn debris into the town’s two reservoirs, leaving only a few days of safe water. Businesses closed, and the town hired trucks to haul 2.2 million gallons from Santa Fe and Santa Rosa. Then, in February 2025, debris combined with bad weather and equipment failure caused a pressure drop, triggering a monthlong boil-water advisory and yet more water shipments.

“The February event was probably the scariest,” Romero said.

State and federal governments have allocated $148 million to rebuild the treatment plant and support efforts to find alternative sources, including drilling wells and reusing water. Groundbreaking on the first phase is slated for Nov. 18, 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 Karen Pettine, who has owned the Hillcrest Restaurant in Las Vegas for 50 years, the water crisis meant closing 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.”

The problem is not limited to the Southwest. In 2020, 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. That same year, Glenwood Springs raced to shore up its treatment system before the spring melt.

Wildfires are a natural part of forest ecosystems, but their increasing severity has made watersheds — the areas that capture, filter and regulate water flow — vulnerable, said Amanda Hohner, an assistant professor at Montana State University who specializes in wildfires and water quality.

Water treatment plants that rely on streams and rivers typically treat high-quality water, aided by trees and soil that act as natural filters, Brucker said. But fires cause spikes in heavy metals and dissolved organic matter that plants are not built to handle. Utilities may be forced to shut off incoming water and switch to other sources, which are not always immediately available.

Reservoirs can act as sedimentation basins, allowing particles to 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 in still water they can fuel algal blooms that make people sick and kill fish.

Chlorine, routinely used to disinfect water, can also react with dissolved organic matter left by fires to form “disinfection byproducts,” which are regulated by the U.S. Environmental Protection Agency because they can cause illnesses, including cancer. Plants must remove the organic matter before disinfecting, which can delay the water supply.

Garrett McKay, an associate professor of civil and environmental engineering at Texas A&M, said utilities are extremely concerned and are reaching out to experts like him for help finding different water sources or learning how to treat the organic matter flowing into their plants.

For communities like Las Vegas, the fixes are expensive and slow. The town’s new treatment plant is a multiyear project, and residents continue to live with the consequences of a fire that burned years ago. Romero said the lesson is clear: “The Gallinas River is something we can’t depend on forever.”