SOURCE: E&E News

DATE: September 11, 2020

SNIP: Historic wildfires raging from California to Colorado are weakening watersheds and setting the stage for deadly mudslides and flooding and, in some places, threatening to poison critical water supplies.

Fueled by record-setting temperatures and strong winds, blazes are wreaking havoc in the West, decimating entire towns like Malden in eastern Washington state, where 80% of the homes and structures — from the fire station to city hall — were burned to the ground.

But the fires don’t just pose a threat to things that burn. More intense and larger fires are also shifting the very ground in Western states. Severe wildfires can change the hydrologic response of a watershed so quickly that even a relatively modest rainstorm can trigger flash floods and steep terrain debris flows, said Jason Kean, a research hydrologist with the U.S. Geological Survey’s Landslide Hazards Program in Golden, Colo.

“A debris flow is kind of like a flood on steroids,” said Kean. “It’s all bulked up with rocks, mud, boulders, and then it becomes a different animal that can be even more destructive than a flood.”

Burned and denuded land no longer has the vegetative root structure to help stabilize the soil and is easily eroded by rain.

Another lesser-known threat to the region’s water is gaining attention in urban areas affected by wildfires: chemical contamination.

In cities that have experienced devastating fires, water officials are finding cancer-causing benzene and other volatile organic compounds in contaminated and fire-damaged water infrastructure.

Such was the case in the Northern California town of Santa Rosa after the Tubbs Fire in the fall of 2017 and again in the town of Paradise after the deadly 2018 Camp Fire. Earlier this week, the carcinogen was detected in the Riverside Grove neighborhood near Boulder Creek, Calif., a community devastated by the CZU August Lightning Complex fires.

As the severity and size of wildfires grow, so do a series of complex threats to the nation’s water systems — from debris to dangerous pollution, depending on the location and type of fire.

Wildfires that only affect wildlands with no urban fill or homes generate sediment and debris that will be washed into nearby bodies of water, all of which can affect smell or taste of drinking water depending on what nearby communities rely upon, said Newsha Ajami, director of Urban Water Policy with Stanford University’s Water in the West program.

If a wildfire destroys homes, cars or other facilities, more concerning debris will need to be managed before the next storm or rain event to control for metals, chemicals and oils. Lastly, there’s no way to control for ash and smoke from wildfires that travel far distances and eventually precipitate on soil and water far from the site of the fire.