Nevada wildfires will result in more water quality challenges, study shows

University of Nevada, Reno researchers studied how wildfire can affect water quality in Lamoille Canyon, a popular choice for hiking and fishing in eastern Nevada. (Photo courtesy Erin Hanan)

Six years ago a massive wildfire blackened one of Nevada’s most popular recreation areas in Elko’s Ruby Mountains. Much of it has recovered since then, but the fire caused lasting harm to water quality and aquatic habitat in the area.

That’s according to a recent study published in the International Journal of Wildland Fire by researchers at the University of Nevada, Reno. 

The massive 2018 wildfire broke out near a shooting range on private land before quickly spreading into the Ruby Mountains’ Lamoille Canyon where it burned through about 5,000 acres of wilderness, leaving behind large amounts of nitrogen-rich wildfire ash that can act as a pollutant in water. 

Researchers spent two years analyzing the wildfire’s impacts on the glacier-carved canyon and surrounding watershed. They chose the area due to its rugged topography, which makes water runoff from burned slopes a major threat to stream water quality.

The study found that in Nevada’s semiarid shrublands a combination of severe wildfire and drought gutted plant growth in the years after the fire, limiting the amount of nitrogen-rich wildfire ash the environment could absorb. If plants can’t quickly absorb excess nitrogen from wildfire, the pollutant is released into streams and lakes where it can cause several adverse health and ecological effects.

The research lines up with other recent studies showing water quality in the western U.S. can remain compromised for nearly a decade following wildfires.

Doctoral student Maxwell Kay Strain led the UNR study under the supervision of Erin Hanan, an associate professor in the Department of Natural Resources & Environmental Science and principal investigator of the Fire and Dryland Ecosystems Lab.

“What we found is that actually two factors are likely to deteriorate water quality: the severity of the burn and increasingly dry conditions after fire,” Hanan said. 

In the study area, nitrogen absorption by plants was reduced in the most severely burned areas, while nitrogen absorption by both plants and soil microbes was muted in the dry conditions following the fire. 

“The vegetation plays a really important role in determining how the system recovers, how well it takes up available nitrogen, and the extent to which nitrogen gets flushed to streams,” Hanan said. 

“When you have a storm that eventually hits, then that nitrogen can just be rapidly flushed into streams where it can act as a pollutant. The key takeaway from this is that as we’re facing more drought, we may be seeing more severe impacts of fire on streams,” she continued.

A parched landscape of chokecherry, wheatgrass and mountain mahogany fueled the Lamoille Canyon fire, which saw flames reach up to 100 feet. 

Researchers found the more intense the fire the less plant regrowth was seen in the following years. Both moderately burned and severely burned areas saw less growth than areas that were not burned. 

Severely burned areas lost plants most adept at absorbing nitrogen-rich wildfire ash, like chokecherry shrubs, further affecting nitrogen absorption and water quality. Researchers observed that chokecherry shrubs in severely burned areas did not resprout, possibly because the fire was sufficiently severe to eliminate the plant’s underground root structure.

“These plants are adapted to fire, and they’re even adapted to severe fire, that’s why they sprout from below ground. But when you hit them with a very severe fire, followed by an intense drought, you might reach a point where recovery is slowed down, and that can have impacts for water quality,” Hanan said. 

The two-year study also found lower plant diversity in areas that were severely burned compared to other areas, likely due to wildfire burning away seeds near the surface.

“The soil is an amazing buffer against temperature and heating. If you go even just a few centimeters down into the soil, there’s a drastic difference in the amount of heat that’s transmitted. And so, it takes a very hot fire to kill off the whole seed bank. But if you’re talking about a species where the seeds are very close to the surface, yeah, those can easily be killed,” Hanan said. 

The study’s implications extend to other semiarid shrublands western United States, not just Nevada. It reveals that increasingly severe wildfires and drier conditions in places such as Lamoille Canyon are threatening ecosystem recovery and water quality in streams across the west.

“This was an important case study that was focused on Lamoille Canyon,” Hanan said. “It’s one of many important examples that show when you combine more extreme fires, climate change, drought and all of these factors, it can really prolong the impacts on water quality.”

Nevada is understudied in terms of fire, with many large fires receiving little attention, said Hanan. The unique characteristics of Nevada’s watersheds, influenced by snow melt and shrub cover, require specific research attention. Future research is needed to understand the specific impacts of fire on different ecosystems and watersheds in Nevada.

The researchers said they hope their findings can help guide pre- and postfire management efforts in wildfire-prone areas, safeguarding waterbodies for recreation and protecting the wildlife that inhabit them.

Wildfire management will be needed as the severity and extent of drought and wildfire increases in the western United States and Nevada. Nevada’s fire season, once limited to late summer and early fall, now spans nearly the entire calendar year.

Last year, nearly 860 wildfires burned about 104,000 acres of land across Nevada, according to the Nevada Division of Forestry.

Nearly one-fifth of Nevada’s land area has been burned by wildfire in the past 40 years, landing the state fifth in the nation for land area burned by wildfires, according to a recent study by the Lied Center for Real Estate at the University of Nevada, Las Vegas.

Rural counties in Northern Nevada were the most affected by wildfires in the state. Elko County – home of Ruby Mountains’ Lamoille Canyon – had the largest percentage of land area burned by wildfire at 41%, followed by Humboldt at 39%, according to the study.