Workshop on Proposed Solutions to Stop the Spread of Invasive Plants in Lake Tahoe | South Lake Tahoe


Event date:

October 29, 2021 – 3:00 p.m.

SOUTH LAKE TAHOE, Calif .– The Tahoe Keys Property Owners Association (TKPOA) and its partners are seeking public input on potential solutions to the spread of aquatic weeds that currently threaten all of Lake Tahoe. They are holding a meeting on Friday October 29 from 3:00 p.m. to 6:00 p.m. at the Tahoe Keys Pavilion, 300-498 Ala Wai Blvd, South Lake Tahoe.

A draft permit for a trial of aquatic weed control methods (National Pollutant Discharge Elimination System or NPDES) prescribing various treatment options is currently under consideration by the Lahontan Water Board.

The Control Methods Test app offers the stand-alone and combined use of a variety of approaches, including targeted herbicides and UV-C light, to reduce and control the abundant growth of invasive and noxious aquatic weeds.

“The CMT will help determine the most effective integrated management methods that will significantly reduce the impacts and threats of invasive aquatic plants on Lake Tahoe and improve management in the Tahoe Keys lagoons,” said Dr. Lars Anderson, specialist Aquatic Ecology / Invasive Species Specialist and University of California affiliate, Davis Weed Science Group. “CMT’s herbicides are specifically chosen to control target aquatic weeds while minimizing impacts on desirable native plants that are currently controlled by invasive weeds. This approach has been used successfully in lakes across the United States that have the same invasive and pest species. “

UV-C light is a new technology that has had some success in small test areas of Lake Tahoe, but has not been tested in a large-scale area with water quality conditions like Tahoe Keys lagoons.

Anderson is a retired aquatic plant biologist who ran the USDA lab at UC Davis. He’s now helping the Tahoe Keys. He started working and surveying the area in 1995 and recognized the problem right away. He said the plants would spread if there was no effective management.

It is not known exactly how the invasive plants entered the lake, but it can be assumed that they made their way from the Sacramento Delta on boats. It could have happened as long as the 1940s and 1950s before people realized it.

“People don’t notice it until they become a problem when they get out of sight,” Anderson said.

He has been trying to give solutions since 1995. Anderson said that the collaboration between the League to Save Lake Tahoe, the TKPOA and the Tahoe Regional Planning Agency will hopefully achieve a solution to weed removal. . He said he is encouraged as there is now greater awareness of the problem.

“You can’t do the same thing as always and expect a new result,” Anderson said.

It is not yet clear what this solution will be exactly, that there is no “quick fix”, but Anderson said it would be a combination of methods.

“The Keys is unique in other areas,” Anderson added.

These invasive plants are difficult to control without a natural enemy. They can fragment and spread the seeds, so extracting them is not a viable solution.

The Curly-leaved Pondweed is one of Tahoe’s newer invasive plants and has grown rapidly like Eurasian Watermilfoil. It is one step ahead of propagation as it forms a stalk (shoot), sprouts, and waits for spring light to be ready to go.

A third problematic plant is actually native to Lake Tahoe, the hornwort. It grows all over the world and likes warmer water that doesn’t move. It has no roots and therefore derives its nutrients from the sediments along the water. It can grow to 20 to 30 feet, but is more common in the first 8 to 12 feet below the surface. As the water recedes, they grow faster because there is more light.

Control methods will use UV light alone in some areas, herbicides alone in other areas, with a third test using a combination of the two. UV takes time to travel around docks and is more effective farther from shore and docks, with this herbicide working better closer to shore, Anderson said.

Another method, laminator flow aeration, creates oxygenation at the bottom of the lake that reduces the level of nutrients for algae, but it has not been tested on other species.

The League to Save Lake Tahoe strongly supports the testing of the proposed control methods, as science clearly shows that aquatic weeds are a serious threat, the status quo will not solve the problem, and the fate of Lake Tahoe is at stake.

“To keep Tahoe Blue, we need to move forward with this thorough and thorough testing of all the methods that could be part of the long-term solution,” said Darcie Goodman Collins, Ph.D., CEO League to Save Lake Tahoe / Keep Tahoe Blue. “This fact is indisputable: if we do nothing, or if we do not act quickly, the worst fate for Lake Tahoe is inevitable.”

There are 170 acres of canals in the Tahoe Keys. The plan under consideration is to use the herbicide on less than 17 acres, and the other two methods on the remainder.

The use of herbicides was very successful in the United States before Anderson said it. TKPOA had not been able to get approval before because the Lahontan Water Board prohibited the introduction of chemicals into the lake. The Environmental Protection Agency and the State Water Board have changed their position and a look at new things to eliminate invasive weeks is allowed.

If approved, this is a three-year project, the first year examining the effect of herbicides and combinations. They then monitor the area for two years and review the results. They will then offer to expand the processes and try to find the most efficient and best way to keep things under control. They will assess how quickly herbicides break down /

“A lot of precautions will be taken,” Anderson said.

The October 29 workshop will provide information on the project – its history, goals, challenges, potential solutions and timeline while soliciting feedback from the community. The open house format will feature various stations where attendees can review information, ask questions and provide feedback throughout the morning. Representatives from various agencies, as well as some leading scientific experts involved in the project, will provide information and be available to answer questions and gather comments. More information will be available at

Aquatic weeds have spread to many areas around Lake Tahoe, creating an emergency and a need for lake-wide collaboration to control them, with the greatest concentration being in the Tahoe Keys. The Tahoe Keys Property Owners Association submitted the application for testing aquatic weed control methods, which required an Environmental Impact Report (EIR) in accordance with the California Environmental Quality Act (CEQA) by the Lahontan Regional Water Quality Control Board (Lahontan Water Board), and an Environmental Impact Statement (EIS) according to the Tahoe Basin Compact by the Tahoe Regional Planning Agency (TRPA). The EIR and EIS are available at (

Since the 1980s, TKPOA has invested millions of dollars to fight ISA and has worked with prominent regulators and the League to Save Lake Tahoe on many concepts including harvesting weeds, collecting fragments, background barriers, bubble curtains and continued research into other new methods. Agencies mobilized their staff in support and matched TKPOA’s investment. This joint effort is now entering a critical period. The public comment period on the proposed permit, which began September 15 and ends November 1, 2021, will be reviewed by the Tahoe Regional Planning Agency (TRPA) Board and the Regional Control Board of Lahontan water quality (LRWQCB) in January. If approved, testing would begin in the spring of 2022, depending on water levels and other natural factors.

The invasive plant spread throughout the lake compromises water quality, degrades recreational uses and threatens the future ecosystem of Lake Tahoe, which is one of the few outstanding national resource water bodies designated by the federal government for United States.

The effects of climate change on the ecosystem add to the urgency. In just five decades, Tahoe’s average water temperature has risen by 1.4 degrees Fahrenheit. Dr Anderson explained that the combination of milder winters, warming in early spring and now drought conditions has exacerbated the invasive conditions of aquatic weeds and harmful algae (cyanobacteria).

The Lahontan Regional Water Quality Control Board is accepting written public comments on the Control Method Testing Permit until 5:00 p.m. on November 1, 2021. Letters of comment can be submitted electronically, by email, with the subject line “Tahoe Keys Weeds Control Test” to the following Email address: [email protected] or submitted in hard copy to: 2501 Lake Tahoe Boulevard, South Lake Tahoe, CA 96150, at attention from Russell Norman.

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