If you were standing The waters of Colorado’s Cache La Poudre River basin may have looked black after the 2020 Cameron Peak fire. The slurry of ash and burnt soil flowed into a reservoir that supplies drinking water to Fort Collins, a downstream city of about 170,000 people. The water cleared again a few weeks later, but Charles Rhodes, a research biogeochemist with the U.S. Forest Service’s Rocky Mountain Research Institute, says the watershed is still seeing contaminants from the fire.
Recent studies have shown that some basins Start recovery Within five years of a fire, other things can change radically, and we may never fully return to pre-fire conditions. And as wildfires become more common, much larger, and burn longer due to global warming, hydrologists, ecologists, and water managers are struggling to understand and mitigate the consequences of fire-polluted water on people and ecosystems.
A healthy forest has a lot of “trash” on the ground—pine needles, fallen leaves, and debris. “It acts like a sponge,” Rhoades says. “When rain falls, it can slowly soak through that layer and seep into the soil.” When fires burn the land, the plants and organic matter are burned, leaving a bare landscape that is highly susceptible to erosion. Rain doesn’t soak into the ground; it just slides right across the surface, moving quickly, picking up soil and carrying it into streams and rivers. This not only creates sediment but can also disrupt the chemistry of the water. Rhoades found that: Increased nutrient levelsLike nitrogen, it was found in rivers nearly 15 years after a major fire. These nutrients can lead to harmful algal blooms, but do not directly affect drinking water quality. However, in other areas, heavy metal levels such as manganese, iron, and even lead can increase after large fires, complicating water treatment processes.
Like other parts of the western United States, Taos, New Mexicoand Santa Cruz, CaliforniaAs climate change and decades of fire suppression practices have increased the frequency and duration of wildfires, we face similar challenges. For much of the 20th century, the U.S. Forest Service and other land management agencies aimed to prevent all fires from burning, believing that this was the best way to protect forests. However, naturally occurring, low-severity fires improve forest health by preventing the accumulation of dense undergrowth and dead trees that serve as fuel.
“We know that 140 years of fire suppression has left an enormous amount of fuel on the landscape, and that, combined with increased severe weather conditions, means that the potential for really intense fire behavior is much higher than it used to be,” says Alyssa Cordner, an environmental sociologist, professor at Whitman College in Washington State, and a volunteer wildland firefighter. “We also have more people living next to forests, and wildfires are moving into the fire-urban interface.” When wildfires burn through watersheds, every community is at risk for water contamination.
“Consumers are rarely aware of everything that goes on under the hood,” says Rhoades. After a wildfire, water providers work tirelessly to ensure residents don’t experience the effects from their taps, which requires collaboration between land agencies such as the Forest Service, USGS and local governments. They conduct regular water tests, install sediment control structures and sometimes change water treatment protocols to handle the increased load of contaminants.
