If you were standing After the 2020 Cameron Peak wildfire, the water gurgling along the banks of Colorado’s Cache la Poudre River might have looked black. This slurry of ash and charred soil flowed downstream toward a reservoir that supplies drinking water to the city of Fort Collins, which has a population of about 170,000. Though the water looked clear again after a few weeks, Charles Rose, a research biogeochemist at the U.S. Forest Service’s Rocky Mountain Research Station, says contaminants from the fire can still be found in the watershed.
Recent studies have shown that in some basins Beginning to recover Within five years of the fires, other forests are fundamentally altered and may never fully return to their pre-fire state. And as wildfires become more frequent, larger, and burn longer with a warming planet, hydrologists, ecologists, and water management officials struggle to understand and mitigate the impacts of fire-contaminated water on people and ecosystems.
In a healthy forest, the ground is littered with a lot of “litter” — pine needles, dead leaves, detritus, etc. “It acts like a sponge,” Rhodes says. “When rain falls, it slowly moves through that layer and soaks into the soil.” When land burns, plant and organic matter is burned, leaving bare earth that’s prone to erosion. Instead of soaking into the ground, rain slides off the surface and moves quickly, picking up soil and carrying it into streams and rivers. Not only does this cause sediment to build up, it can disrupt the chemistry of water. Rhodes says, Increased Nutrient LevelsNearly 15 years after the devastating fires, rivers are still showing high levels of nitrogen and other heavy metals. These nutrients don’t directly affect drinking water quality, but they can lead to harmful algal blooms. But elsewhere, after the devastating fires, concentrations of heavy metals like manganese, iron, and even lead have been elevated, which can complicate water treatment processes.
Other parts of the American West, e.g. Taos, New Mexicoand Santa Cruz, CaliforniaThe United States faces similar problems, as wildfire frequency and duration increase due to climate change and decades of fire suppression. For much of the 20th century, the U.S. Forest Service and other land management agencies aimed to prevent all fires, believing that was the best way to protect forests. However, naturally occurring, low-intensity fires improve forest health and prevent the accumulation of dense undergrowth and dead wood that provide fuel.
“140 years of fire suppression has left a lot of fuels building up on this land, and as a result, combined with an increase in severe weather, we’re finding that the potential for really intense fires is much higher than it used to be,” says Alisa Cordner, an environmental sociologist, professor, and volunteer wildland firefighter at Whitman College in Washington. “We’re also seeing more people living next to forests and moving into places that are at the wildfire-urban interface.” Any municipality is at risk of water pollution if wildfire burns through a watershed.
“Consumers have little knowledge of everything that’s going on below the surface,” Rose says. After wildfires, water utilities work tirelessly to ensure residents don’t experience water impacts. This requires coordination with land management agencies like the Forest Service, USGS, and local governments. Water utilities regularly test water quality, install sediment control structures, and sometimes change water treatment protocols to address increased contaminants.
