It’s not only trees — wildfires imperil water too

Sediment-choked watersheds and erosion could become more frequent as wildfire activity grows.

 

The Fourmile Canyon Fire, sparked by a backyard burn west of Boulder, Colorado, in 2010, caused $220 million in damage and destroyed 168 homes. It also scorched nearly a quarter of a watershed that supplies water to the nearby community of Pine Brook Hills. The problems didn’t end there: Long after the blaze was put out, intense rainstorms periodically washed sediment and other particles downstream, disrupting water treatment and forcing the local water district to stop pulling water from Fourmile Creek, leaving it reliant upon water already collected in its reservoir.

“The water coming down Fourmile Creek would get so dirty that we simply would shut down moving any water (from the creek),” for days or even weeks, says district manager Robert de Haas. “If we hadn’t built the reservoir” — in 2006 — “we’d have been in big trouble.”

Now, new research suggests that such water-quality problems might become more frequent across the West. Climate change is already causing a surge in wildfire activity. As a result, scientists expect to see a rise in erosion in most of the region’s watersheds in the coming decades. Sediment and ash running off burned hillsides into streams can clog reservoirs, smother fish and disrupt municipal water supplies.

In many places, however, water managers and other officials are already taking steps to prepare for both wildfire and its long-term aftereffects. For communities that rely on forested drainages for their water, “It is a key aspect of water supply and watershed protection to plan for a wildfire,” says Kate Dunlap, who works on source water protection for the city of Boulder.

Fourmile Fire crewmembers clean branches and mud out of Colorado’s Boulder Creek in 2011, after the Fourmile Canyon Fire scorched vegetation in the area in 2010 and subsequent summer monsoons washed sediment and debris downstream.
Cliff Grassmick/Daily Camera

In forested watersheds — the source of 65 percent of the West’s water supply — trees, soil and leaf litter soak up precipitation like a sponge, then slowly release it to aquifers, streams and rivers. But wildfires can sear the soil, making it water-repellant, and incinerate stabilizing plant roots. “Then, when it rains, all that water gets transported right off the surface,” ferrying sediment, nutrients and debris downstream, says Jeff Writer, a hydrologist at the University of Colorado Boulder. Sometimes precipitation triggers deadly mudslides that destroy homes and bury highways. Sediment can also shroud streambeds and reservoirs, forcing managers to dredge or conduct other costly fixes.

Floods of sediment and debris can also compromise water supplies. Spikes in nutrients can spark algae blooms, causing taste and odor problems. Small particles can clog filters. When organic matter reacts with treatment chemicals, it can create toxic compounds like chloroform. After the Fourmile Canyon Fire, Pine Brook Water District had to revamp its water treatment process to avert those noxious byproducts. “(These problems) can basically shut the whole plant down,” Writer says, though typically only for short periods of time. Still, the problem highlights the importance of having more than one municipal water source.

One of the lessons of the Fourmile Fire, which Writer and other researchers studied at length, was that both vigilance and patience are required post-fire. The fire occurred in September, leaving a 10-month gap before summer monsoons hit, causing severe erosion. Water managers may need to monitor flood forecasts, rainfall intensity and water quality for months or even years after fires.

“Even though fire is a natural component of (many Western ecosystems), there is a concern about increases in erosion and sedimentation, and increases in fire,” says Joel Sankey, a research geologist with the U.S. Geological Survey in Flagstaff, Arizona. Research he carried out with colleagues suggests that more than a third of Western watersheds could see their sediment load double by 2050, due to climate change and post-fire erosion, putting surface water supply and quality at risk. “There’s an opportunity for communities, watershed managers, to proactively respond to the information,” he says. Many are already doing so. Cities like Flagstaff, Arizona, Boulder and Fort Collins in Colorado, and Santa Fe, New Mexico, are thinning forests, stepping up water monitoring and studying watersheds to identify which areas are most susceptible to erosion.

Federal and local agencies can also reduce the threats to water quality by responding quickly after wildfires occur. Strategies include protecting bare ground with mulch to reduce erosion and building retention ponds to capture sediment before it can clog intake pipes at treatment plants, says Stephanie Kampf, a hydrologist and professor at Colorado State University. When blazes blast through urban areas, as this year’s deadly wildfires in Northern California did, toxic ash and remnants of paint and plastics add to the substances that can be swept downstream. Officials there are using sandbags to keep debris out of storm drains and taking other measures to protect water quality following the fires. “Wildfires are a natural part of the landscape — and they’re inevitable in the Western U.S.,” Kampf says. “I think that preparing for them, to minimize vulnerability to fire, is really the way to go.”

Emily Benson is an HCN editorial fellow.

High Country News Classifieds
  • 10 ACRES OF NEW MEXICO HIGH DESERT
    10 Acres of undeveloped high desert land in central NM, about 45 minutes from downtown Albuquerque. Mixed cedar and piñon pine cover. Some dirt roadways...
  • WATERSHED RESTORATION DIRECTOR
    $58k-$70k + benefits to oversee watershed restoration projects that fulfill our strategic goals across urban and rural areas within the bi-national Santa Cruz and San...
  • CUSTOMER SERVICE ASSISTANT - (PART-TIME)
    High Country News, an award-winning media organization covering the communities and environment of the Western United States, seeks a part-time Customer Service Assistant, based at...
  • OPERATIONS DIRECTOR
    We are a Santa Fe-based nonprofit that builds resilience on arid working lands. We foster ecological, economic, and social health through education, innovation, and collaboration....
  • COMMUNITY ORGANIZER
    Come work alongside everyday Montanans to project our clean air, water, and build thriving communities! Competitive salary, health insurance, pension, generous vacation time and sabbatical....
  • CAMPAIGN MANAGER
    Oregon Natural Desert Association (ONDA), a nonprofit conservation organization dedicated to protecting, defending and restoring Oregon's high desert, seeks a Campaign Manager to works as...
  • HECHO DEPUTY DIRECTOR
    Hispanics Enjoying Camping, Hunting, and the Outdoors (HECHO) was created in 2013 to help fulfill our duty to conserve and protect our public lands for...
  • REGIONAL REPRESENTATIVE, COLUMBIA CASCADES
    The Regional Representative serves as PCTA's primary staff on the ground along the trail working closely with staff, volunteers, and nonprofit and agency partners. This...
  • FINANCE AND OPERATIONS DIRECTOR
    The Montana Land Reliance (MLR) seeks a full-time Finance and Operations Director to manage the internal functions of MLR and its nonprofit affiliates. Key areas...
  • DIRECTOR OF CONSERVATION
    The Nature Conservancy is recruiting for a Director of Conservation. Provides strategic leadership and support for all of the Conservancy's conservation work in Arizona. The...
  • EXECUTIVE DIRECTOR
    The Amargosa Conservancy (AC), a conservation nonprofit dedicated to standing up for water and biodiversity in the Death Valley region, seeks an executive director to...
  • BIG BASIN SENIOR PROJECT PLANNER - CLIMATE ADAPTATION & RESILIENCE
    Parks California Big Basin Senior Project Planner - Climate Adaptation & Resilience ORGANIZATION BACKGROUND Parks California is a new organization working to ensure that our...
  • SCIENCE PROJECT MANAGER
    About Long Live the Kings (LLTK) Our mission is to restore wild salmon and steelhead and support sustainable fishing in the Pacific Northwest. Since 1986,...
  • NEW BOOK BY AWARD-WINNING WILDLIFE BIOLOGIST, BRUCE SMITH
    In a perilous place at the roof of the world, an orphaned mountain goat is rescued from certain death by a mysterious raven.This middle-grade novel,...
  • MOUNTAIN LOTS FOR SALE
    Multiple lots in gated community only 5 miles from Great Sand Dunes National Park. Seasonal flowing streams. Year round road maintenance.
  • RURAL ACREAGE OUTSIDE SILVER CITY, NM
    Country living just minutes from town! 20 acres with great views makes a perfect spot for your custom home. Nice oaks and juniper. Cassie Carver,...
  • A FIVE STAR FOREST SETTING WITH SECLUSION AND SEPARATENESS
    This home is for a discerning buyer in search of a forest setting of premier seclusion & separateness. Surrounded on all sides by USFS land...
  • CARPENTER WANTED
    CARPENTER WANTED. Come to Ketchikan and check out the Rainforest on the coast, HIke the shorelines, hug the big trees, watch deer in the muskeg...
  • CAUCASIAN OVCHARKA PUPPIES
    Strong loyal companions. Ready to protect your family and property. Proven against wolves and grizzlies. Imported bloodlines. Well socialized.
  • ENVIRONMENTAL GEOPHYSICS
    "More Data, Less Digging" Find groundwater and reduce excavation costs!