Aquatic invasive plants have taken root in shallow waters around Lake Tahoe, threatening the lake’s prized clarity, water quality, ecology, recreation and economy.
Why this is important
Aquatic Invasive Plants are a Widespread Problem
Around the Country
USGS Map of Aquatic Invasive Plants, 2018
Aquatic invasive plants are a challenge for numerous bodies of water around the country, costing billions of dollars each year, according the the US Fish and Wildlife Service. Click here to see how other areas around the west are handling the challenge.
Around Lake Tahoe
Bureau of Land Management Map of Aquatic Invasive Plants, 2017
Aquatic invasive plants affect all marinas and numerous shallow, warm areas around Lake Tahoe and continue to spread, constituting the most immediate threat to Lake Tahoe, according to the University of Nevada, Reno's 2015 Implementation Plan for the Control of Aquatic Invasive Species within Lake Tahoe. Curlyleaf pondweed, able to grow in deeper, colder waters, has begun to spread more rapidly than Eurasian watermilfoil.
In the Tahoe Keys
Tahoe Keys Curlyleaf pondweed distribution map, 2016
More than 95 percent of the Tahoe Keys' 172-acre lagoons are infested with aquatic invasive plants. Tahoe Keys Property Owners Association has both aggressively managed these plants with available methods and proactively sought long-term solutions to bring the infestation under control once and for all.
Why This is Important
Harvesting is the primary control method available to the Tahoe Keys today. In 1984, roughly 100 cubic yards were removed from the lagoons and nearly 10,000 cubic yards were removed in 2017. In spite of these efforts, which cost $400,000 a year, Tahoe Keys Property Owners Association is clearly losing ground with these approved tools. Find out more about current efforts.
At the same time, conditions in the lake are becoming more and more hospitable for these plants, with the UC Davis Tahoe Environmental Research Center 2017 State of the Lake Report showing the water warming 10x faster than normal.
The continued spread of these aquatic invasive plants could rapidly transform from a nuisance to a very real threat to the environment, water quality, recreation and the economy of Lake Tahoe. These plants can harbor other non-native species and create ideal habitat for mosquitoes.
History of Efforts
We have been working to control the plants in the lagoons by looking for long-term, integrative solutions for decades, working with a broad-range of scientific experts, associations and agencies to vet an exhaustive list of potential plant control measures while examining and evaluating new techniques and technologies as they arise. .
TKPOA is committed to solving the invasive plant problem and has so far spent $3,700,000 to manage the invasive plants and to develop improved methods. We're expected to spend another $2,500,000 by 2020. This funding comes from special assessments paid for by the property owners, along with grant funding and other private funding.
The 1,500 Tahoe Keys property owners consistently support invasive plant management strategies in and out of the water including: Voting for a special assessment to continue funding the invasive plant management program.
TKPOA has collaborated with the Tahoe Regional Planning Agency, the Tahoe Resource Conservation District and US Forest Service since 2011. We have also worked with the League to Save Lake Tahoe to implement ways to prevent plant fragment spread.
Reducing the volume of weeds helps to ensure that other methods are more effective and fragments do not enter Lake Tahoe. TKPOA's best management practices that are used to reduce weeds include:
TKPOA's current methods:
Non-Point Source (NPS) Plan/ Lake Friendly Landscaping
The Lake Friendly Landscaping program summary
TKPOA's proposed methods:
The following methods are currently being tested or evaluated by TKPOA as solutions to our invasive weeds problem:
Floating Islands: This technology uses native wetland plants on a floating matrix. The roots extend into the water providing a very large surface area through which nutrients are absorbed and removed from the water. The islands may also be deployed with fine-bubble aerators to create water circulation to push more water through the root system. The vendor estimates that a 0.5-HP compressor can push enough air through the aerators to move 12.4 million gallons per day. Status: This technology requires securing funding and permitting.
Circulation System Reactivation
EcoSoar: EcoSoar utilizes an all-natural scientific process to both create and inject superoxide anion radicals (SOAR) into the water column and sediment to clean and restore the water body to a natural, healthy state. Status: The EcoSOAR vendor has agreed to provide a 3-month test of their unit along with installation and technical support, at no cost. TKPOA will need to pay for permitting, electricity and monitoring.
Laminar Flow Aeration: Laminar Flow Aeration (LFA) involves bubbling air through several small diffusers on the bottom of the lagoons. The air bubbles cause the water to circulate, increasing the amount of oxygen at the bottom of the lagoons, which in turn facilitates changing the form of some of the nutrients in the sediment and “muck”. This change is intended to make the nutrients less available for the weeds and algae, which should reduce the rate and amount of weed growth in the area of the LFA test. Status: TKPOA is applying for permits from various regulatory agencies to test a technology called Laminar Flow Aeration (LFA). TKPOA has received financial support for this project from The League to Save Lake Tahoe. The test will be conducted in the lagoons adjacent to Christie Drive, north of Venice Drive.
UV Light Treatment: UVC light damages the DNA and cellular structure of the plants, causing them to die. The light energy goes into the plant and essentially sunburns and scars the outer tissue. It also causes a cell fusion and they can no longer reproduce. Status: This method is currently being tested at the Lakeside Marina. Depending on the outcome of the UV light test, this method could also be one of TKPOA’s many tools in their integrative approach to managing the invasive plants.
Well-monitored, localized use of EPA and Cal/EPA approved selective herbicides in specific areas of the lagoon: While TKPOA is committed to the integrative and long-term control of invasive plants, the reality is that the current approved methods are not enough to reduce the infestation to the point where the methods can keep up with the growth across the 170 or so acres that make up the lagoons. Along with other proposed methods outlined earlier, TKPOA is proposing a short-term, highly managed spot use of herbicide in specific areas of the lagoons, away from the main channel and far from the entrance to Lake Tahoe. The aim is to efficiently reduce invasive plant growth to a level where all methods can be integrated effectively and thereby reduce the need for harvesting.
Further information on the proposed EPA approved herbicides
The proposed aquatic herbicide treatment, as outlined in the Tahoe Keys Lagoon Restoration Project proposal, is as follows:
The project performance criteria for the herbicide use is as follows: