Caldor wildfire smoke and ash impact study focuses on Lake Tahoe’s health

As flames from the Caldor Fire swept up and over the summit of the Sierra Nevada, long-time Lake Tahoe researcher Sudeep Chandra from the University of Nevada, Reno assembled a team of scientists for a rapid response to gather samples of smoke and ash that could harm the fabled lake's ecology and clarity.

“With this rapid response research, we’re pushing the boundaries of science to learn about wildfire impacts, help inform critical fire recovery decisions and create a model that can be used in other places facing threats from extreme wildfire," Darcie Goodman Collins, CEO of the League to Save Lake Tahoe, one of the organizations funding the research, said.

The Tamarack, Caldor, and Dixie fires burning near the Lake Tahoe basin have been impacting the air quality for weeks to months in the summer of 2021, and impacts may continue into the fall.

“At Lake Tahoe, the water quality and clarity are declining due to particles in the water,” Chandra said. “This study is trying to address how much smoke comes to the lake and fertilizes the living particles versus how much of the smoke is just depositing nonliving or inorganic particles, both causing the water quality and clarity to decline.”

Chandra, professor of biology at the University, is leading the team of researchers across five institutions to study the effects of wildfire smoke on Lake Tahoe. He is director of the University’s Global Water Center, the Ozmen Institute for Global Studies and the project’s principal investigator.

“The frequency and recurrences of these fires is going to force us to rethink what our restoration goals are for clarity,” Chandra said. “What if we have to manage to 30 feet of clarity instead of 60? What type of biodiversity might we have in the watershed and lake with the increase in fires which are expected to occur with drought conditions? These are the questions our bistate California-Nevada Tahoe Science Advisory Council will want to answer in the coming months. While these are all challenging questions, they are also present opportunities."

With 18 of California’s 20 largest recorded wildfires taking place in the past 10 years, the impacts of the wildfires and smoke will become increasingly relevant to the Tahoe basin as well as other lakes around the world.

"While we are focused on understanding the impacts of wildfire smoke on Lake Tahoe, it is likely that smoke influences the function of lakes and rivers globally as well as within our region," Chandra said. "It will depend on the duration of the fire, the intensity of smoke and where and how far it is transported. This summer the wildfire smoke generated from California traveled across North American and into Europe.

"The smoke changes light conditions above the lakes and rivers and deposits particles and ash. One thing is for certain, society and our environment has been influenced by fires in the past. We know from previous studies examining the past that fires can impacts lakes and rivers, the question becomes how these current, intense and more frequent fires will influences ecosystems in the future.”

Visible changes
The team has already made some visual observations of the lake changing from the wildfires. Chandra said the water is visibly greening along the beaches at the south shore of Tahoe, and he has seen large clumps of algae growing in the lake. There are ash particles accumulating near the shores, and private homeowners in the southeastern corner of the lake have said their water intake filters are clogging from the particles. This usually happens over the course of months but took just days when smoke from the Caldor Fire blew into the Tahoe Basin.

"Other potential negative effects from the wildfire include altering the biological diversity within the lake," Chandra, also director of the University's Limnology Lab, said. "Many species native to the lake have been in decline for decades. Understanding how the lake will change from wildfire smoke is key to conservation efforts for those species, many of which are endangered."

The lake’s clarity has implications for people, too.

"The local economy relies on tourism," Blaszczak said. "Decreased clarity, water quality at the edge of the lake, or smoke conditions in the air could lead to less visitation into the watershed. Further, residents in the Tahoe Basin rely on the lake for drinking water, and less clean water could affect drinking water quality."

This research follows close behind the Global Water Center smoke effects on lake ecology study completed on Castle Lake in Northern California. The researchers found the lake changed considerably following six wildfires in 2018 that led to smoke hanging over the water.

“It takes a science village to save a lake," Chandra said. "The science and management cultures are interwoven at Tahoe and focused on preserving and restoring the watershed and lake. There is plenty of historical science information to draw from to understand the impacts from this fire.”

The research was jump started by $70,000 in donations from the League to Save Lake Tahoe, which allowed researchers to collect the time-sensitive data they needed while other agencies worked on budgeting to support the project. In three weeks, the team secured $211,000 in funding from the University of Nevada, Reno, U.C. Davis, the Tahoe Regional Planning Agency, the Tahoe Fund, the State of California and the State of Nevada.

“As we learn to live with the prospect of more intense wildfires threatening the Tahoe Basin as a result of climate change, we must rely on the best available science from our research partners to guide decision making,” said Julie Regan, Deputy Director of the Tahoe Regional Planning Agency. “We must pivot to align our policies to build resiliency in the face of these unprecedented challenges of catastrophic wildfire and smoke impacts.”

Regional Buffers
"We protected the lake from invasive species by creating regional buffers which included boat washing stations at Lake Mead, Donner Lake and other nearby lakes," Blaszczak said. ".Now we’re dealing with smoke and ash. We may have to create a regional buffer of forest management to reduce the risk of intense wildfires close to the Basin that can increase smoke in the Tahoe airshed.”

She and Chandra feel that implementing fire management plans regionally could be an approach to conserving Tahoe for future generations.

“For 40 years we’ve been in the mode of protecting the Tahoe Basin based on actions that happen in the basin," Chandra said. These fires, the Dixie, the Tamarack and the Caldor clearly show that we have to protect Lake Tahoe by thinking about actions outside of the Lake Tahoe Basin. The watershed has had fires in the past and previous indigenous societies have lived with or used fire in the region. Maybe looking at the past can inform the future” Chandra said.

“The Caldor Fire has provided us a glimpse into the conditions Lake Tahoe may continue to experience each fire season,” Blaszczak said. “We hope our study offers new insight into how to best manage and protect Lake Tahoe in this new era of extreme wildfires and smoke.”

— Mike Wolterbeek is a Communications Officer for the University of Nevada, Reno