‘ACT’ing to find the way back to deep water clarity for Lake Tahoe
SOUTH LAKE TAHOE, Calif. — Living at Tahoe comes with a multitude of positives, ranging from beautiful views to world class slopes to unlimited lake access.
But living in paradise comes with a price, and one of them is the quality of the deep water in the basin.
“Lake Tahoe has experienced a decline in water clarity since the late 1960’s, starting with the region’s development boom,” said US Environmental Protection Agency Press Officer Joshua Alexander. “Between 1986 and 1997 deep water clarity declined by approximately 30% from about 97 to 64 feet. Since then clarity has stabilized somewhat, to an average of 64.4 feet between 2016-2021.”
The decline of Lake Tahoe’s clarity can be largely attributed to fine sediment particles and algae. Research has found that fine sediment particles, nitrogen, and phosphorus are the main pollutants affecting the lake, and primary sources of those pollutants include urban and forests upland runoff, atmospheric deposition, and stream channel erosion.
“Urban development, increasing tourism, and climate related disturbances are all growing challenges for Lake Tahoe’s water quality,” said Alexander. “EPA has been charged with supporting protection of the Tahoe Basin ever since Section 114 of the 1972 Clean Water Act required implantation of a study to ‘preserve the fragile ecology of Lake Tahoe.’”
The need for EPA’s involvement grew in 1997 after that years Tahoe Summit, which set air and water quality goals and started the word of EPA’s Lake Tahoe Basin Coordinator.
There have been multiple ways since that agencies around the basin have attempted to measure and maintain the clarity of Lake Tahoe.
The Secchi Disk
When Lake Tahoe’s clarity is measured, a Secchi disk is used. The disk is typically 20 centimeters and alternates with white and black quadrants.
“The Secchi disk is lowered into the water from a boat until it is no longer visible, which is called the Secchi depth,” said Alexander. “Clarity and other health indicators have been measured at Lake Tahoe since 1986, helping to inform strategies to protect the lake.”
The operation of using the Secchi disk is something that has stayed consistent for years, and continues to allow scientists to identify changes and patterns in lake clarity.
Lake Tahoe Total Maximum Daily Load
The Lake Tahoe Total Maximum Daily Load is a plan that was developed by state agencies in both California and Nevada and approved by the EPA in 2011. The Lahontan Regional Water Quality Control Board and the Nevada Division of Environmental Protection created the plan to reverse the impact on water clarity in Lake Tahoe, and provides oversight of implementation efforts to reduce the amount of pollutants that are discharged in the lake.
“The TMDL program embodies the roadmap for reducing pollutant loads to the lake,” said Alexander. “The TMDL developed a strategy to achieve pollutant load reductions through many specific actions including improved roadway operations and maintenance, targeted street sweeping, infiltration basins to capture and treat urban stormwater, and stabilizing eroding slopes.”
The plan continues to allow for a path to lake clarity restoration and identifying causes of clarity decline, pollutant sources, and optimum control strategy. Overall, the TMDL lays out the roadmap to reduce load reductions of the largest pollutant sources to achieve a target clarity of 78 feet by 2031, with the long-term goal of 97 feet by 2076, according to Alexander.
“Lake Tahoe’s water quality faces challenges tied to climate change, such as wildfires, large runoff events, increasing temperatures and proliferation of invasive species,” said Alexander. “Continued progress toward achieving the goals in the TMDL requires collaboration and dedicated resources.”
Working with Agencies Far and Wide
The largest opportunity to reduce fine sediment particle loads resides with the urban stormwater runoff, according to NDEP Environmental Scientist Jason Kuchnicki. Urban stormwater runoff is a mixture of precipitation, suspended sediment, natural and anthropogenic debit, and chemical pollutants that are washed off urban landscape during rain events.
“Our strategy really hinges on urban stormwater load reductions,” said Kuchnicki. “That primarily resides with the local governments in California and Nevada, as well as the transportation agencies.”
There are seven urban implementers that include El Dorado County, Placer County, Washoe County, Douglas County, the city of South Lake Tahoe, California Department of Transportation and Nevada Department of Transportation. Together, they focus on the primary strategies to reduce loads.
The first is water quality improvement projects, which are currently happening all over the basin. This includes projects like the Bijou Area Erosion Control Project, which sees the city of South Lake Tahoe treat stormwater runoff from 47 acres of highly impervious roadways and commercial properties. Caltrans was key in helping plan, fund, and implement the project.
“[These projects are] taking a comprehensive look at individual areas with high loading areas in particular and implementing solutions there,” Kuchnicki said.
Solutions include installing storm water treatment BMPs (best management practices), or infiltration basins to infiltrate stormwater runoff so that it doesn’t flow directly into the lake. Another solution is the implementation of erosion control measures like permeable pavers put onto road shoulders to prevent parking and other thing that could cause erosion.
Agencies also focus on advanced road operations. Kuchnicki explained that almost a decade ago, there was a shift in taking care of the roads with CalTrans and NDOT, especially in the wintertime
“They’re using very sophisticated equipment to target their applications and minimize their applications,” said Kuchnicki. “A lot of times they might not even apply sand to the roads, they may just apply a solution which lowers the freezing point of the road.”
The use of highly advanced street sweepers have also helped the reduction of runoff.
“They have the capability of actually vacuuming the road so they can suck up these fine sediment particles directly from the road and adjacent shoulders.”
The League to Save Lake Tahoe Focuses In
One non-profit working to improve Lake Tahoe’s clarity is the League to Save Lake Tahoe and their Tahoe Blue Crews. Together, staff and volunteers around the lake set up events and clean-ups aimed to clean up the lake and the surrounding environment, including the beaches.
“To keep Tahoe blue, we A.C.T. – Advance restoration, combat pollution, and tackle invasive species,” said the League’s Chief Strategy Officer Jesse Patterson. “To restore the lake’s clarity, we first need to eliminate the things that are currently threatening it, like litter, aquatic invasive species and pollution from our urban areas and roads. At the same time, we’re working to enact broad-scale restoration so the lake’s natural, clarity-preserving functions are firing on all cylinders.”
The League’s goal is to ultimately help make the lake resilient to fires, droughts, and all other impacts from climate change.
Aside from fine sediment particles and trash that make its way into the lake, another battle the League is fighting is against invasive species, especially aquatic weeds.
“They outcompete native plant species and create inviting habitats for other, more harmful invasive species like fish to move in,” said Patterson. “And when the weeds die, their biomass releases huge amounts of nutrients that fuel even more aquatic plant growths and can prompt harmful algal blooms.”
If the algae and invasive plants don’t get checked, Tahoe’s shallow waters could become unrecognizable.
Combatting littering is another huge priority of the League. While volunteers play a huge role in the amount of litter picked up on the beach yearly, the League also uses BEBOT, the West Coast’s first beach cleaning robot, who found thousands of pieces of small trash this summer buried below the sand at Tahoe beaches.
“It’s the things people don’t think about that are the biggest source of trash entering the lake,” said Patterson. “It could be the corner of a food wrapper that falls out of your pocket, the banana peel you leave on the ground because it’s ‘natural’ or even pieces of broken plastic sled that got buried in the snow in the winter. Eventually, any trash left in the basin will flow into the water.”
Litter data collected by volunteers after clean-ups helps the League understand the sources of the pollution to then identify and push for solutions.
“Just a month ago, the city of South Lake Tahoe passed a ban on single-use plastic water bottles,” said Patterson.
The City cited the League’s litter data as one of the reasons for their decision, since plastic bottles were one of the most commonly found litter items during their beach cleanups. According to Patterson, the same can be said for local bans on plastic bags and polystyrene.
“Data helps us stop litter at the source,” said Patterson.
It Starts at Home
Although much of the work to restore lake clarity lies with agencies and counties doing their part, there are plenty of things that homeowners and community members can do to help.
The Tahoe Regional Planning Agency is able to help implement parcel BMPs through regulations that require all parcels in the basin developed install onsite BMP to retain runoff, onsite pollutants, and prevent pollutants from running off on their parcel.
“It’s really critical to maintain those BMPs,” said Kuchnicki. “They might work for a few years, but if they’re not being regularly maintained, then their efficiency can go way down.”
Choosing to use phosphorus free fertilizers is another way to help reduce sediments in the lake, along with native plants to the Lake Tahoe area.
Replacing wooden stoves is another way to make an impact. The TRPA has an incentive program that helps homeowners replace old wooden stoves with more energy efficient ones in order to reduce primarily nitrogen emissions and fine particles that can burn off and make their way into the lake.
“It’s kind of a newer concept, but people can adopt a storm drain,” said Kuchnicki. “It’s not applicable in all cases where people might live next to a storm drain where runoff goes to, but sometimes, if a jurisdiction hasn’t been out there sweeping, you might find some sediment accumulated around those storm drains.
“So if you happen to be in that circumstance, it would be great if folks could sweep that up and put in in their trash. That way, next time it rains, it doesn’t get washed down the drain.”
The League to Save Lake Tahoe offers volunteer programs like the Tahoe Blue Crews, who adopt certain areas to conduct clean-ups at multiple times a year. Anyone can also use the Citizen Science Tahoe app to report environmental issues they find in the area.
“Anyone, resident or visitor, can live the Keep Tahoe Blue lifestyle,” said Patterson. “That means enjoying all Tahoe has to offer, but making sure you leave this special place better than you found it. If you see trash, pick it up. Walk, ride your bike, or take a micro-transit shuttle instead of driving your car. Be what we call a Tahoe Blue-Gooder. Whether you have five minutes or five hours, we make doing the right thing the easy, fun, and rewarding thing.”
Looking Forward to the Future
The goal is to one day reach at least 97 feet in lake clarity measurements by the time we reach the year 2076. But it won’t happen overnight. The TMDL analysis suggests that it’s going to be hard, but not impossible.
“The plan requires a 65% low reduction in fine sediment particles, and around a 35% low reduction in phosphorus and a 10% low reduction in nitrogen,” said Kuchnicki. “Those are some pretty aggressive targets to meet. That analysis suggested that it’s achievable and that was anticipated to take about 65 years.”
Currently, the TMDL only represents a ten year plan to restoration, and so far, performance is on target.
“The 10 year review and overall finding is that yes, we did achieve the 10 year milestones for urban storm water as well as the non-urban source categories,” said Kuchnicki.
So far, there hasn’t been a change in lake clarity since 2000, according to Kuchnicki. Although they’ve halted the decline, there are many factors at play that could change this, including the changing climate and possible ecological changes in the lake. Currently, the NDEP is working with the Science Advisory Council to investigate those drivers and see what extent they can control lake clarity at.
Anyone at home can track lake clarity and other TMDL projects at clarity.laketahoeinfo.org.
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