While scary and catastrophic, experts stress that wildfires are a natural—even expected—process. Much of the landscape of western Colorado and southern Utah is expected to have a “mixed severity fire” in wooded areas every 35 years or so, according to a report from the Forest Service in 2000.
While wildfires are expected, they are growing in both severity and frequency due to climate change. Hot, dry conditions increase fire risk by producing dry natural fuels but also because warmer, drier air increases the prevalence of lightning, the biggest natural cause of wildfires.
A handful of active wildfires are being fought in Utah, but two large fires in Colorado have burned major portions of watersheds that pour into the Colorado River and could affect the communities along that river for years to come.
The effects of wildfires don’t just end when the fire is put out. The shockwaves of a large or particularly severe fire can echo through an area for decades through water quality issues, soil erosion, debris flows and landslides, and even from the detrimental effects from fire retardants used to help control the flames.
Keeping an eye on the watershed
Soot and runoff from wildfires can affect watersheds, as can a variety of fire retardant chemicals, usually dropped from aircraft, to limit the spread of fire.
Ammonium sulfate, usually found in fertilizers, is mixed with guar gum and red dye, to create a fire retardant that is particularly effective when wet, but still works even when dry. The ammonia in the compound, however, can be toxic to fish and other aquatic life if dropped on smaller streams. Firefighters are using both fire retardant drops as well as water drops to fight the Grizzly Creek Fire, as large areas of the region the fire is burning are far too steep for hand crews to dig a fire line and fight the fire on the ground.
Fortunately, the Incident Management Team dealing with these fires are taking careful steps to limit watershed damage. Currently, the National Interagency Fire Center’s Burned Area Emergency Response Team (BAER), which usually only deals with the aftermath, showed up to manage the ongoing situation.
“Usually the containment is a little further along before we start assessments, but we’re doing them in Glenwood Canyon because of I-70 and the city of Glenwood Springs’ water supply,” said Matt Boyd, the Public Affairs Officer for White River National Forest.
The aircraft teams are also being careful to not drop retardant within 300 feet of streams and to only use water that doesn’t contain invasive species, like zebra mussels, according to reporting from The Colorado Sun.
Long term effects from fires
Heavy rains following current wildfires can also affect water quality along the Colorado River. Even if large events like debris flows don’t occur, the surface of the soil often becomes “hydrophobic” immediately after a fire, meaning that water runs quickly down the slopes rather than absorbing into the soil.
Eventually, soot and loose soil make their way into the river where the debris can kill fish and aquatic plants and cause algal blooms.
Grasses, shrubs and trees that once held the soil together may no longer be there, and in their place ash-filled holes can dot the blackened landscape.
This is particularly an issue in steep terrain, where large boulders may have been held in place by roots and the soil no longer has a vegetated support structure to keep it in place.
For an area like Glenwood Canyon, this could mean devastation.
The major interstate highway I-70 splits the iconic limestone and granite canyon, but fire officials are worried that landslides and debris flows could block and damage the highway for years to come.
Although we have had a weak monsoon year so far, that may not last long, according to Matt Jeglum, the Incident Meteorologist for the Grizzly Creek Fire.
While a light or average rainfall could help with fire containment, a heavier rainfall might put steep terrain at risk for landslides and debris flows.
After 1994’s South Canyon Fire, which burned only 2,115 acres, a debris flow dumped over 25 tons of mud and debris, closing a three-mile-long stretch of the highway.
Currently, the Colorado Department of Transportation is allowing traffic through the Glenwood Canyon corridor but has closed all rest areas and pull-offs, cautioning drivers that landslides and loose debris might become an issue at any time.
Colorado fires likely to affect river corridor for years