Colorado wildfires cause winter snowpack to melt rapidly, threatening watershed for millions of Americans

As record-breaking wildfires and historic drought continue to plague portions of the western United States, researchers have now learned the burn scars left behind in the Rocky Mountains are impacting the viability of critical watersheds for tens of millions of Americans. 

According to Colorado State University researchers, burn scars in high-altitude regions of the Rocky Mountains drastically impact snowpack and runoff for water resources that provide drinking and irrigation water for much of the United States. 

Daniel McGrath, a geoscientist and professor at CSU, surveyed burn scars with his team throughout Colorado to see how fires along critical watersheds go on to deteriorate snowpack and melt. 

McGrath specifically focused his studies on the Cameron Peak Fire burn scar. The Cameron Peak Fire is Colorado's largest fire on record, burning more than 208,000 acres in 2020.  

The Cameron Peak Fire was one of several fires that devastated Colorado's mountains in 2020, many of which grew to be among the largest fires in Colorado history.  

"These fires are burning at higher level severities and higher elevations," McGrath told CBS News Colorado's Dillon Thomas. "We saw more (high altitude Colorado) forest burn in that year than the previous 36 years combined." 

Millions of Americans rely on winter snowstorms in Colorado to provide drinking and irrigation water during summer and fall. 

Climatologists have been following climate change's impact on water resources stemming in Colorado for decades now. 

However, now that wildfires are becoming more frequent and more difficult to contain, McGrath set out to learn how the annual snowpack reacts to the newly charred terrain. 

What McGrath and his team learned was concerning, especially after realizing the impacts of a burn scar can take more than a decade to correct.  

"As we increasingly see these fires impacting the highest elevations of the west where we accumulate these deep seasonal snowpack, there is concerns about what that means for these (water) resources," McGrath said. "What we found in the Cameron Peak Fire specifically is we saw about a 20% reduction in the amount of the snowpack that accumulated." 

Wildfires like the Cameron Peak Fire burn so hot, with flames reaching so high that the canopy is often destroyed. Without a canopy snow throughout the winter falls directly past the burned trees and to the ground.  

"At first you might think you might see an increase in snow accumulation because you don't have this intercept that is occurring. But, because we lose the forest, we see increases in windspeeds and other fluxes through the forests which can lead to sublimation, which is when it goes from a solid state to a vapor state," McGrath said.  

Not only is less snow being retained on the ground, but that which does remain in the snowpack is also melting much faster than areas not impacted by fire.  

"(The snowpack is melting) anywhere from about 80% to 140% faster than unburned sites close to our study plots," McGrath said. "The snow disappeared 11 to 13 days earlier from the burned landscape than it did from the unburned landscape." 

CBS News Colorado's Dillon Thomas recently reported that CSU researchers found layers of dust blowing from the southwestern corner of the state that also caused more rapid melting. That dust is not caused by fires, but has a similar effect.

Much like the dust on the snow, ash and more left behind by wildfires, also causes the snow to melt faster during sunny days.   

"Tree remnants and stumps shed dark, sooty material onto the snow surface which changes how reflective the snowpack is," McGrath said.  

The dark soot left behind by the fires causes light to be absorbed into the snow, causing more rapid melting. That results not only in snow melting faster, but less water being retained in soil.  

"That can impact seedling survival. So, it is also coupled with how that landscape will regenerate and revegetate post fire," McGrath said.   

McGrath says the more rapid melting will likely not result in increased concerns for flooding in Colorado. However, that does not mean the impacts of the burn scars on the snowpack will stay confined to the state.  

An estimated 50% to 70% of water resources in the western United States come from the Rocky Mountains.  

"We are already stretched so thin in our water resources," McGrath said.  

With massive burn scars causing earlier runoff, there are concerns water resources may be even more limited in late summer and early fall months. 

On top of drinking water, Americans across the west rely on that very water to produce vegetables, fruits and more that end up in stores for major cities such as Las Vegas, Los Angeles and more.  

"So, each year that we see increases in wildfire across the west, we are accumulating the impact across the region and increasingly impacting these essential water resources," McGrath said.  

McGrath says as of now, there are not clear ways that humans can directly solve this issue. Once the fires start and grow, the damage is already done. 

There are ways that Coloradans are working to prevent wildfires from growing. 

Teams not only are helping clear dead and dry debris throughout the summer and burning them in piles in the winter. But, teams are also working to conduct large controlled burns that will serve as a barrier in the case of future fires along the watershed.

Other entities, many of which are operated by Colorado municipalities, are going in to burn scars and trying to remedy the impacts by dropping wood chips onto portions of the burn scar along rivers, in an effort to try and get more water to absorb into the ground. 

McGrath says the findings of CSU's research should serve as a warning to the human race to take climate change more seriously and to take action to prevent wildfires that are becoming more frequent as a result of climate change.  

"These impacts last for much longer than the single year of the fire," McGrath said. "All of the citizens of the western U.S. are going to be impacted directly by these fires occurring in this region."