When #Wildfire Burns A High Mountain Forest, What Happens To The Snow? — KUNC

A burnt sign on Larimer County Road 103 near Chambers Lake. The fire started in the area near Cameron Peak, which it is named after. The fire burned over 200,000 acres during its three-month run. Photo courtesy of Kate Stahla via the University of Northern Colorado

From KUNC (Luke Runyon):

To understand, and possibly predict what happens after a river’s headwaters goes up in flames, researchers are descending on newly created burn scars across the West to gather data in the hopes of lessening some of the impacts on drinking water systems.

On a sunny winter morning, a team of researchers led by Colorado State University hydrologist Stephanie Kampf roamed through the steep drainage of Tunnel Creek, a tributary to the Poudre River. Much of the creek burned this summer and fall during the Cameron Peak Fire west of Fort Collins, Colorado…

For more than an hour and a half, Kampf’s team searched for a flat spot to construct a temporary weather station. The university received a National Science Foundation grant to put instruments into the field quickly, before snows began to accumulate in the burned area. At more than 208,000 acres, the burn scar is the state’s largest on record.

Two other nearby fires broke size records in 2020 as well. In late October the East Troublesome Fire exploded near the headwaters of the Colorado River, burning 193,812 acres, killing two people and causing thousands to flee their homes. To the north, the Mullen Fire on the Colorado-Wyoming border topped out at 176,878 acres. Downstream on the Colorado River, the Grizzly Creek Fire torched 32,631 acres in and around Glenwood Canyon. And in the Book Cliffs north of Grand Junction, Colorado, the Pine Gulch Fire burned nearly 140,000 acres.

In the case of Cameron Peak, which acts as the headwaters for the Poudre River, Kampf and her colleagues want to know: what happens to the snow that falls on a burned area this high in elevation and this big?

“Some of these streams have burned so much, like the whole riparian zone is burned. And so there’s nothing alive at all,” Kampf said…

Existing research shows fires can affect snowpack in different ways. With fewer trees, and without their full, bushy branches, more snow tends to accumulate on the ground. Snow that’s caught in trees often blows off or turns immediately to vapor. So when a wildfire moves through a forest, scientists say to expect more snow to pile up on the ground.

But the lack of tree cover also causes that accumulated snow to behave differently. Without a shaded canopy above it, the snow is more exposed to the sun, and in the spring, melting can become erratic. Mid-winter melting can occur, which means a lessened runoff come spring.

These general findings can change, depending on the type of forest that burned, the direction the burned slope is facing, and the severity of the burn in that area…

Studies of dust on snow have shown its dramatic effect on the timing of snowmelt. The same is true of snow that’s been mixed with charred debris and smoke particles, [Anne] Nolin said. “All that black guck on the snow makes it melt a lot faster,” she said.

A mis-matched timing of snowmelt makes the job of reservoir management much harder, Nolin said. Many water providers use long-term models to gauge when to release and store water. A burned drainage area makes those historical data less reliable…

With water supply margins already tight in many portions of the West, Boisrame said, water providers, agriculturalists and environmental groups are realizing, “that we actually need to know” the detailed effects of how each individual burn scar will affect the water cycle.

That’s because no two fires are alike. Depending on weather and fuel loads, each fire burns a landscape with varying severity. And that severity matters, not just for forest recovery, but also for water quality immediately following it, said Ben Livneh, a University of Colorado-Boulder engineering professor.

“The most severe impacts actually come from moderate severity fires,” Livneh said.

In fires with lots of high severity burn, much of the vegetation is completely combusted. Dissolved organic carbon can be one of the biggest headaches for water treatment facilities following a fire. Treating it can also result in byproducts found to be carcinogenic, Livneh said. But if there’s not much organic material left in a burned area — because it all burned — it doesn’t cause as many problems.

“And so maybe somewhat counterintuitively, the most severe fires aren’t necessarily the most damaging, at least from a water treatment and water quality perspective,” Livneh said.

Research has shown too that forest management can play a big role in lessening the impacts of fire on water systems. The Desert Research Institute’s Boisrame looked closely at one creek in Yosemite National Park. In that watershed, land managers have been more hands-off with fire suppression, and allowed smaller fires to burn more frequently…

One hurdle in understanding the relationship of burn scars and snowpack is that it’s a challenge to get good data from such dynamic environments. Landslides and floods after a fire can destroy scientific instruments.

That was top of mind for Colorado State University’s Kampf as she traversed the Cameron Peak burn scar. Finding a site for a weather station is like looking for a proper campsite. Researchers want something flat, on stable ground and free from large hazards like falling rocks and trees. That’s often hard to find in a recently burned forest…

The weather station along Tunnel Creek will be compared to another site untouched by fire. Other stations will look at impacts at higher and lower elevations. They’re likely to collect data on soil moisture, solar radiation and precipitation for the next three to four years, Kampf said, though long-term funding hasn’t yet been secured.

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