TAHOE CITY, Calif. – July 9 marked 50 years since Tahoe Environmental Research Center founder Charles R. Goldman launched the John Le Conte on Lake Tahoe, a vessel still used today, setting an important milestone in the voyage of research and monitoring of Lake Tahoe.
“I think sometimes we focus on the problems that we see in front of us,” TERC Director Dr. Stephanie Hampton said at the start of this year’s State of the Lake report on Thursday, July 16. “I also want to remember that we need to celebrate some of the successes of the past.”
And so, she began this year’s presentation, held at Granlibakken in Tahoe City, looking back at the rich legacy set by Dr. Goldman. In addition to founding a research dynasty, the pioneer worked with the founders of Keep Tahoe Blue, fought for stricter environmental protections, like diverting sewage out of the basin, and helped thwart a four-lane highway proposed over the mouth of Emerald Bay.
These actions have been instrumental in preserving the environmental destination Lake Tahoe is today, drawing many from far and wide.
Hampton noted that Tahoe now relies on a $10 billion-a-year tourism industry. Despite being half the size of Yosemite National Park, it receives three times the visitation, presenting the region with a new wave of challenges in managing these influx pressures.
“One of the things that I really love about working and living up here is that nobody needs to be convinced that the environment needs to be protected,” she said. “Most people live or visit here because of the environment. So, the questions are mostly about how to protect it.”
To answer those questions, TERC and partners look to science.
Tahoe’s clarity
Although not used alone, Tahoe’s famed clarity is a good indicator scientists use to monitor its health.
After declining through the nineties, annual average clarity continues to plateau at about 70 feet.
“So that’s good news, that these declines seem to have stopped,” Hampton explained, “but many people in this room aren’t aware that the management target for Tahoe is to reach historical levels. The Tahoe community wants more. They really want to protect and restore this lake.”
That means the aim for clarity is a depth of 97.4 feet by 2076 and an interim goal of 78 feet by 2031. Hamption explained that there are variations in clarity, with winter values holding steady while summer values worsen. The highest clarity values occur during deep-mixing events, when the lake mixes vertically from the surface to the bottom.
Much of the focus on restoring Tahoe clarity has been on inorganic particles, such as sediment, after a 2006 study found that 58% of inorganic particles contribute to clarity impacts, while organic particles account for 25%.
However, Hampton pointed out, “When we don’t see that [clarity] curve bending in spite of all of our efforts to try to improve clarity, we have to ask whether this information is still true.”
A warming world
Since the time that study concluded, Hampton explained, air and water temperatures have been warming. Those changes have brought increasingly more precipitation as rain and less snow, as well as more ash and smoke as fires grow more frequent and intense.
As these environmental factors change, ecosystem drivers may also be changing and impacting clarity.
Rain can often wash more sediment into the lake compared to snow. Ash and smoke can also contribute to sediment and affect clarity. Additionally, ash introduces nutrients to a class of organic particles, called phytoplankton, which are microscopic organisms that can impact clarity.
The concept has TERC researchers taking a closer look at phytoplankton. These small creatures, unlike inorganic sediment (which sinks), remain suspended in the water column, exerting a persistent impact on clarity.
One decline in clarity in June and July of 2025 correlated with a large bloom of one phytoplankton called Cyclotella.
Phytoplankton also thrive in warm temperatures.
“So, it stands to reason,” Hampton said, “that phytoplankton may be a bigger driver of clarity as water warms.”
Understanding phytoplankton
Hampton outlined numerous methods to monitor these microscopic beings.
One method includes using the same laser technology used to detect blood cancers at the UC Davis Comprehensive Cancer Center. Researchers have found a way to use the technology to detect one of the smallest phytoplankton, called picoplankton, which is too small to be measured by standard methods.
Although picoplankton are incredibly small, a study found that they account for around 50% of primary productivity in Tahoe, highlighting their significant role.
Studies are also being conducted on “lake snow,” seemingly snow-like large particles that fall to the bottom. These are made up of aggregations of phytoplankton and sediments that stick together.
Why are they important to clarity?
These aggregates sink faster than individual particles, thereby going out of the light zone and no longer impacting clarity. Understanding “lake snow” could be an important piece of the puzzle.
“We’re trying to understand how the environment shapes how particles actually get cleared from the upper waters and how fast it can occur,” Hampton explained. “So we think understanding these processes will be key to understanding why summer clarity is not improving.”
Nearshore
Hampton also provided an overview of an ecosystem where humans interact most with the lake and where the greatest pressure from aquatic invasive species occurs—the nearshore environment.
One of the greatest concerns the public and researchers have in this area of the lake is algae and whether it is increasing.
“So far, we cannot detect a change in the total amount of near shore algae, but here’s the big caveat,” Hampton said. “It is really difficult to monitor near shore algae because it is literally a moving target.”
It can jump from one zone to another, so if it moves out of the monitoring area, that data no longer gets captured.
To combat this, TERC researchers are developing new monitoring methods using drones and helicopters to capture data on the entire shoreline.
A grad student is also studying whether satellite remote sensing can effectively monitor shoreline algae. Although TERC is cautiously optimistic, Hamptson said, “if it works, that would be very cost-effective and potentially semi-automated.”
Other shoreline studies are using genetic approaches to investigate how algal patches are associated with invasive species and testing the use of DNA in the environment to detect invasive species.
Hamption concluded the State of the Lake by addressing broader implications.
“This get-together in Tahoe tonight is focused on Lake Tahoe, but the lessons learned here go well beyond this place,” Hampton said. “Looking forward we’re going to anticipate that the challenges will intensify as areas of North America become less hospitable through heat, storms, sea level rise and wildfire.”
Populations are expected to shift northward and to higher elevations, something already seen at Tahoe, which receives an increase of visitors by the thousands when Central Valley temperatures go above 100 degrees.
“As the world changes,” Hampton said at the end of the report, “it’s likely that this is just the beginning, so we need to build resilience in our communities and our infrastructure, our ecosystems now.”
To read the entire State of the Lake Report, visit tahoe.ucdavis.edu/stateofthelake.
