Pop Quiz: What’s the largest wildfire in Colorado history?
A) East Troublesome Fire B) Pine Gulch Fire C) Cameron Peak Fire D) Hayman Fire
Answer: C. Cameron Peak Fire
The three largest wildfires in Colorado history have all burned in 2020. The Pine Gulch Fire briefly claimed the title as the largest, burning 139,007 acres, before being surpassed by the Cameron Peak Fire seven weeks later. The Cameron Peak fire has burned nearly 209,000 acres and the East Troublesome Fire has consumed 193,774 acres claiming the number two spot. (Neither Cameron Peak nor East Troublesome fires were 100% contained at the time of this writing.)
“We see instances where as little as a quarter- to a third-inch of rain can trigger debris flows.”
Beyond the tragedy of lives, structures, and acreage lost, these fires have long-term impacts on Colorado’s larger ecosystem and water supply.
One principle concern is that scorched soil doesn’t absorb even small amounts of rain. Trees and shrubs that typically help hold dirt and debris in place are drastically reduced or eliminated. This makes burn scars more susceptible to events like landslides and increased sediment in the watershed which can impact water quality, storage capacity and water conditions for fish and wildlife.
“We see instances where as little as a quarter- to a third-inch of rain can trigger debris flows,” said Kevin Houck, chief of the watershed and flood protection section of the Colorado Water Conservation Board.
The U.S. Forest Service’s National Interagency Fire Center’s Burned Area Emergency Response team (BAER) typically arrives at a fire after it has been contained to help address repair, rehabilitation and restoration of terrain damaged by flames and suppression work. Recovering from a fire and safeguarding waterways from increased runoff is a massive coordinated effort. National agencies, like the U.S. Forest Service, and state, cities, counties, water districts and other parties with vested interests often come together for mitigation efforts.
The initial assessment is mostly focused on impacts to major roadways and water and power infrastructure for the surrounding communities.
“We may look at environment later on,” said Lisa Stoeffler, deputy forest supervisor for the White River National Forest, “once we have a final footprint of the fire. The BAER process is really looking at things that we would need to address because it would cause an emergency-type situation.”
Increased Landslide Risks Post-Wildfire
BAER has already been studying satellite imagery and fire growth in the yet-to-be-contained Grizzly Creek fire (32,631 acres) to assess possible debris flows that could clog the Colorado River or block I-70 in a rain storm.
The increased risk of catastrophic landslides along I-70 have already prompted federal geologists to install more monitoring sensors in efforts to create earlier warning systems for potential landslides along Colorado’s most trafficked thoroughfare to the mountains.
Wildfire’s Impact on Endangered Fish
“You pray for rain, but at the same time this would be a tough time to get a flow of ash and retardant off the burned area.”
The Grizzly Creek fire has also sparked specific concerns for the Colorado River’s endangered fish downstream. Heavy sediment load in runoff, especially if combined with a low baseflow (a not unlikely scenario given our ongoing drought conditions), could suffocate fish.
“There’s a probability we could have an effect all the way down into the 15-mile reach,” said Tom Chart, director of the U.S. Fish & Wildlife Service’s Upper Colorado River Endangered Fish Recovery Program.
The 15-mile reach is home to four species of endangered fish. This stretch often has less water than is recommended because of two large irrigation diversions that pull water from the river to irrigate Grand Valley Farms. This problem spot is one where water managers already constantly work to bolster water levels through upstream reservoir releases. These managers have already reported seeing fish use fish ladders to swim up and downstream in search of deeper, cooler waters.
“The potential with the Grizzly Creek Fire could be as bad as it gets if we get a rainstorm on top of a low baseflow,” Chart said. “You pray for rain, but at the same time this would be a tough time to get a flow of ash and retardant off the burned area.”
Preventing the sediment-heavy runoff from reaching the river might be impossible. So the best bet, according to Chart, would be tapping into upstream reservoir water to flush the sediment and ash from the waterways.
This will take heavy coordination between the already heavy demands on that limited water supply. But it’s a collaboration already underway and will continue for years to come. “That landscape is going to take a long time to heal,” Chart said.
Municipal Water Quality & Supply
Without vegetation to slow down run off, municipalities with water supplies in or near the wildfire burn areas expect to see more sediment in the reservoir.
The City of Greeley, for example, relies on four river basins for their water supply: Big Thompson, Laramie, Cache la Poudre and Colorado River basins. All four basins were impacted by fires this year. The Colorado River Basin by the East Troublesome fire and the remaining three by the Cameron Peak Fire.
“The Poudre basin alone has five reservoirs that serve municipal purposes,” explains Jen Petrzelka, Water Resource Operations Manager for the City of Greeley. “And all five were burned. They were burned to different severities, but all did experience some burn around them.”
The burns along the reservoirs will lead to increased sedimentation. Initial modeling predicts that Greeley will see a 10-17x’s increase in sedimentation, which will reduce storage capacity and water quality. But mitigation efforts are already underway.
The Coalition for the Poudre River Watershed, formed after forest fires in 2012, is leading efforts between the U.S. Forest Service; the cities of Greeley, Fort Collins, and Loveland; Laramie County; area water districts; the state; congressional delegates and even ditch companies.
The first goal is to prevent excess sediment from getting into the reservoirs. Once it’s there, there are only two paths forward: dredge the reservoir to reduce sediment and maintain storage capacity (a very costly solution), or increase treatment of the water to maintain water quality (which also comes with much higher treatment costs).
Efforts to prevent sediment from entering the reservoirs are underway already and began in the first week of November. They include:
· Mulching
· Using downed trees to create a barrier
· Creating “wattles”, a mix of mesh and local vegetation.
Petrzelka notes that everything gets a lot harder once there’s snow on the ground, so most mitigation efforts will take place in the coming spring.
The partners know that the effort will be long and costly. The High Park Fire that impacted the area in 2012 took three years for completion of mitigation efforts and that fire was smaller–burning 87,284 acres in total.
Estimates from the Poudre River Watershed Coalition place the cost for mitigation from this year’s fires at $50 million with an unknown timeline.
Long-term funding and fire prevention efforts are also underway. Natural Resources Conservation Service (NRCS) through its Emergency Watershed Protection Program has already provided funding and is working closely with stakeholders to secure additional funding. Water providers and others are working closely with the US Forest Service to secure and apply funding for preventing future fires.