Confluence: Wildfires threaten region’s watersheds
A record-breaking wildfire season that has included the massive Cameron Peak and East Troublesome fires — as well as the smaller-but-still-destructive CalWood fire in Boulder County — will have long-lasting and major effects on water supplies in the Boulder Valley, Northern Colorado and beyond.
That was the message from panelists in the “Fire in the Watershed” panel at Confluence: Colorado Water Conference, a virtual event organized by BizWest, Thursday. The panel took place as several wildfires continue to rage: the Cameron Peak fire, which has grown to become the largest in state history, at 206,000 acres; the East Troublesome fire in Grand County that exploded to 125,000 acres Wednesday night; and the CalWood fire, which has burned about 10,000 acres in Boulder County.
Jennifer Kovecses, executive director of the Coalition for the Poudre River Watershed, said wildfires constitute an important element in sound forest management, as fires eliminate fuels, release seeds of lodgepole pine cones and encourage forest renewal.
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“It’s a given in the West that wildfires are an important part of the ecosystems,” she said. “Our ecosystems, especially our forested headwaters, have evolved over time to interact with wildfires. They have shaped what our forests and headwaters look like.”
But past forest-management approaches encouraged rapid responses to extinguish fires, she said, which allowed for a buildup of fuels over time.
“The unintended consequence of this management approach really was that as we tried to extinguish all fires, we ended up allowing fuels to build up in our forests because we stopped that interaction of wildfires, the role that wildfires played in reducing those fuels.”
The result is that wildfires have become more intense and with bigger footprints, in some cases burning the top layer of soil itself.
“The outcome of that is some pretty significant changes in our watersheds in a post-wildfire environment,” she said. “After the fires go out, that’s when the problems really start.”
The result affects a broad swath of the region’s economy, including not only the quality and safety of raw drinking water but also supplies for the brewing, chip-manufacturing and other sectors such as recreation and whitewater rafting.
She noted that all of the headwaters for the region’s water supply lie within the Cameron Peak burn area.
She said that forest managers need to think big when it comes to restoration.
“We need to work at a larger scale, sort of at the same scale of size of restoration that these wildfires are,” she said, planning restoration projects at that scale and bringing managed wildfires back into those ecosystems.
“Unfortunately, the Cameron Peak fire has done some of our work for us, ahead of our plans,” she said.
Stephanie Kampf, professor of watershed science at Colorado State University’s Department of Ecosystem Science and Sustainability, said the 2020 wildfires present a series of challenges for the region’s water supplies.
“In this massive wildfire season, it is quite shocking to see how much has burned,” she said.
She noted that 2012’s High Park fire, which burned more than 87,000 acres in Larimer County west of Fort Collins, had “a huge impact” on the region’s watershed, and is now dwarfed by the Cameron Peak fire.
While the Cameron Peak Fire will affect the Poudre River and Big Thompson watersheds, the CalWood fire in Boulder County will affect the St. Vrain River watershed, she said, with the East Troublesome Fire affecting the Western Slope’s collection system.
Kampf said the problems begin on hill slopes that are no longer protected by vegetation. Normally, water from rain and melting snow will infiltrate the ground and gradually make its way into the watershed. Without vegetation to hold it, however, water moves over the surface, capturing sediment as it flows. Erosion carves into the landscape and creates gully systems.
That can lead to slope failures, with no vegetation or roots to hold soil in place, creating debris flows and landslides.
Rainstorms can also create a flash-flood hazard, and fast-moving water can carve into river and stream beds, taking more area than normal flows, while sediment can cause channels to fill up.
Post-fire mitigation efforts can include spreading mulch within burn areas to slow down water, and creating large culverts to divert water and sediment farther downstream.
She warned that the current wildfires, which have come late in the season, might cause greater problems because of the lack of snowpack to mitigate or slow runoff.
Chuck Rhoades, a research biogeochemist with the U.S. Department of Agriculture’s Forest Service, said some of the forests that are burning today could be 100 years old, with some “much older,” with fires consuming trees that are 300 to 500 years old.
There is also great overlap with the current fires and areas that have been infested with bark beetles over the past couple of decades, leaving dead trees across a vast acreage of forest land and providing fuel for wildfires.
“It’s a situation that is incredibly unique,” he said, noting that the Cameron Peak, East Troublesome, CalWood and other, smaller fires, “are kind of closing together,” creating one massive burn area.
Such scope not only will cause erosion but also will remove nutrients that will make forests less productive in the future. That, in turn, can cause problems for water supplies, including algae and increases in bacteria, nitrogen, alkalinity, metals, turbidity and other factors.
“Some of these effects can last for quite a long time,” he said, noting that effects of 2002’s Hayman Fire northwest of Colorado Springs — which until this year was the largest in Colorado history at 138,000 acres — are still being felt.
“We have decades-long effects of wildfires,” he said.
Jared Heath, a watershed specialist for City of Fort Collins Utilities, said that given the negative consequences of wildfire impacts on water supply, “It’s really important that we understand the changes to these impacts on our drinking-water quality.”
One advantage for the city of Fort Collins, he said, is the dual nature of its water supply, with drinking water coming from both the Cache la Poudre River watershed and from Horsetooth Reservoir, fed by the Colorado-Big Thompson Project.
During the High Park Fire and Hewlett Gulch Fire of 2012, the city shut down the water supply from the Poudre River because of water-quality impacts, he said, opting to rely solely on Horsetooth Reservoir for a time.
That dual-supply system provides the city with some options when wildfires occur. But, he said, “The biggest threat to our utility is if both supplies were to be impaired at the same time.”
He said the city also has implemented an early-warning water-quality response system, which uses sensors to identify unacceptable levels of turbidity, pH, temperature, dissolved oxygen and conductivity.
“This system allows us adequate time for our operations to shut down our Poudre River pipeline and treat Horsetooth water,” he said.
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