Engineers examine effects on land and water after wildfires are extinguished
The three largest wildfires in Colorado’s known history all occurred in 2020. More than 600,000 acres burned, with the Cameron Peak Fire alone causing $6 million in property damage.
While the last embers of the Cameron Peak Fire are long since extinguished, researchers are increasingly worried about how the remnants of those burns — and future fires — may threaten water supplies across the West.
Environmental engineering Professor Fernando Rosario-Ortiz said the chemical reactions that occur during a wildfire can lead to health and safety concerns when contaminants are released into water, in addition to the more visible and immediate effect on air quality.
“This is especially true in the context of fires at the wildland-urban interface, where if a home burns, we are talking about combusting everything inside those homes — from cleaning chemicals to, potentially, electric vehicle car batteries,” he said. “Better understanding all of those reactions with exposure to water is something that we will definitely need to explore further over the next few years.”
A researcher from Rosario-Ortiz’s lab collect water samples from a creek running through a burn area.
Wildfires are becoming increasingly common in Colorado and the West, thanks to climate change and land management processes over the last 30 years, which sought to suppress wildfires as quickly as possible. That combination has resulted in longer, more intense wildfire seasons that lead to larger, more intense burns due to dense vegetation growth.
When it comes to water and wildfire, though, Rosario-Ortiz and his colleagues are increasingly interested in the “burn scars” fires leave behind. Wildfires destroy the vegetation that holds soil in place. Without it, heavy rains can push mud and sediment onto interstate highways. Or carry bacteria and freshly formed toxic compounds from the fire into freshwater supplies — causing headaches for treatment facilities. Meanwhile, water contamination from burns could also limit freshwater sources during tight drought seasons.
Rosario-Ortiz and colleagues have been going into the field to collect samples from burn scars in California, Colorado, Kansas and Alberta, Canada, for analysis in the lab. They hope to better understand how ash can affect watersheds as it creates and spreads a wide range of potentially harmful organic compounds.
“Our results from that work show the complexity of how a wildfire can impact water quality,” Rosario-Ortiz said. “(Our recent study in Science of the Total Environment) is the first of its kind to identify a specific suite of aromatic acids in wildfire ash and surface water samples. And it will help with the broader discussion and understanding around the nature of dissolved organic matter and the impacts of wildfire on water quality and drinking water sources.”
While Rosario-Ortiz and others are focused on water quality and chemistry, Assistant Professor Ben Livneh is studying these kinds of issues from another direction. As a physical hydrologist, he and his research group explore how climate and landscape changes affect how much water is available in an area — and when. His work also examines how fires and rain can influence landslide risk.
His team is working on NASA-funded research that studies 5,000 landslide sites around the world. So far, they found that sites that had a fire in the past three years required less precipitation to cause a landslide.
Soil and water samples from Bennett Creek in the Rio Grande National Forest.
“But there’s also a lot of local variability that really matters,” said Livneh, who was also recently appointed director of Western Water Assessment. “We now have a lot of people who have built structures on steep slopes in these areas, so there’s a human element there, too. And the time of the year that it happens can be crucial. For example, when a fire occurs right before a large storm can be critical, like we saw in Glenwood Springs, Colorado, this past summer.”
Livneh added that as rain becomes more prevalent due to climate change, leaders, researchers and communities affected by slides and other interrelated problems will have to keep an open mind and work together to solve them.
“Management is a policy problem, and in the next 10 years we’re going to continue to have these big fires and see their impacts,” he said. “But the more open-minded we can be about managing for these things, the better. I’m kind of an optimist. As humans, we’ve overcome so many technical challenges, and I think we can continue to do so here and in the future.”