Proposed aquatic weed control in the Tahoe Keys subject of public workshop

SOUTH LAKE TAHOE, Calif. – The first in a series of in-person workshops to discuss potential solutions to the spread of aquatic weeds that threaten all of Lake Tahoe is scheduled Saturday, Oct. 9. It will be held at the Tahoe Keys Pavilion at the end of Ala Wai Blvd. in South Lake Tahoe from 9:00 a.m. to 12:00 p.m.

A proposed permit for an aquatic weeds control methods test (National Pollutant Discharge Elimination System or NPDES) is currently under consideration before the Lahontan Water Board.

The Control Methods Test application proposes the stand-alone and combined use of various approaches including targeted herbicides and UV-C light to reduce and control the abundant growth of invasive and nuisance aquatic weeds.

“The CMT will help determine the most effective, integrated management methods that will greatly reduce the impacts and threats of invasive aquatic plants on Lake Tahoe as well as improve management in the Tahoe Keys lagoons,” said Dr. Lars Anderson, an aquatic ecology/invasive species specialist and a member of the University of California, Davis Weed Science Group. “The herbicides in the CMT are specifically chosen to control the target aquatic weeds while minimizing impacts to desirable native plants that are currently being suppressed by the invasive weeds. This approach has been used successfully in lakes throughout the U.S. that have the same species of invasive and nuisance plants.”

The UV-C light is a new technology shown to have some success in small test areas of Lake Tahoe but has not been tested on a large scale area with water quality conditions like the Tahoe Keys lagoons.

The Oct. 9 workshops will provide background on the project – its history, goals, challenges, potential solutions, and timeline, while soliciting input from the community. The open house format will include various stations where attendees can review information, ask questions, and provide input throughout the morning. Representatives of various agencies as well as some leading scientific experts involved in the project will provide information and be available to address questions and take comments. Subsequent meeting information will be available on https://tahoekeysweeds.org/.

Aquatic weeds have spread to many areas around Lake Tahoe creating an urgency and necessity for lake-wide collaboration to control them, with the greatest concentration being found in the Tahoe Keys. The Tahoe Keys Property Owners Association submitted the Aquatic Weed Control Methods Test application, which required an Environmental Impact Report (EIR) per the California Environmental Quality Act (CEQA) by Lahontan Regional Water Quality Control Board (Lahontan Water Board), and an Environmental Impact Statement (EIS) per the Tahoe Basin Compact by the Tahoe Regional Planning Agency (TRPA). Both the EIR and EIS are available at (https://www.waterboards.ca.gov/lahontan/water_issues/programs/tahoe_keys_weed_control/).

Since the 1980s, TKPOA has invested millions of dollars to combat AIS and worked with prominent regulatory bodies and the League to Save Lake Tahoe on numerous concepts including weed harvesting, fragment collection, bottom barriers, bubble curtains, and supported research on other new methods. The agencies have mobilized their staffs in support and matched the TKPOA investment.

This joint effort now enters a critical period. The public comment period on the draft permit, which began Sept. 15 and ends Nov. 1, 2021, will be considered by the Tahoe Regional Planning Agency Board (TRPA) and the Lahontan Regional Water Quality Control Board (LRWQCB) in January. If approved, testing would start in the spring of 2022, depending on water levels and other natural factors.

The invasive plant spread throughout the lake is compromising water quality, degrading recreational uses, as well as threatening the future ecosystem of Lake Tahoe, which is one of only a few federally designated Outstanding National Resource Water bodies in the U.S.

The effects of climate change on the ecosystem are adding to the urgency. In just five decades, Tahoe’s average water temperature has increased 1.4 degrees Fahrenheit. Dr. Anderson explained that the combination of milder winters, early spring warming and now drought conditions have together exacerbated the invasive nuisance aquatic weed and cyanobacteria conditions.

“Taken together, these changes enable earlier establishment and more rapid growth of aquatic invasive weeds and algae both in the Tahoe Keys lagoons and in Lake Tahoe. The need for more effective management of these plants is clear: Continuing the status quo will not provide adequate protection of Lake Tahoe,” Anderson said.