Aquatic invasive plants affect all the marinas 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.
The comparatively warm and shallow waters of the Tahoe Keys lagoons make for the perfect habitat for the aquatic invasive plants (Eurasian watermilfoil and curly leaf pondweed).
Ongoing harvesting programs pulled roughly 100 cubic yards of weeds in 1984 - around 10,000 cubic weeds were removed in 2016. They have now taken over more than 90 percent of the 172-acre lagoons.
The infestation, which continues to grow despite harvesting efforts that have cost as much as $400,000 per year, threatens the ecosystem, water clarity, native species and could harbor other non-native species. It can also provide ideal habitat for mosquitoes.
The Tahoe Environmental Research Center’s 2017 State of the Lake report describes record-breaking temperature increases for Lake Tahoe, which enhance conditions for the growth of the aquatic invasive plants.
Annual monitoring of the invasive plants in the Keys lagoons is showing rapid expansion of curly leaf pondweed, which can spread into larger areas of Lake Tahoe than Eurasian watermilfoil, and can pose a significant threat to public water supply systems and the many beneficial uses of the lake.
INTEGRATED MANAGEMENT PLAN
The main goal of the Tahoe Keys Integrated Management Plan is to gain control over aquatic invasive weeds and nuisance weeds in the Tahoe Keys lagoons, which are a major part of the greater Tahoe Keys development.
The plan aims to reduce the biomass (overall volume) of these weeds – curly leaf pondweed, coontail and Eurasion watermilfoil – by about 80% or more.
Control vs. Eradication
Total elimination of the invasive weeds is likely impossible, due to source banks (seeds and other materials buried in the sediment that could regrow) and ongoing re-introduction from other parts of Lake Tahoe.
But by reducing the weeds’ volume significantly, they become much easier to control, minimizing the impacts of control methods, and become much less likely to spread from the Tahoe Keys lagoons to the greater Lake Tahoe area.
Control also helps:
NONPOINT SOURCE WATER QUALITY MANAGEMENT PLAN
Tahoe Keys Property Owners Association has been proactive in tackling runoff and the sediment, nutrients and pollutants it introduces into the lagoons and Lake Tahoe, implementing water conservation goals and landscaping rules to that end.
The Association banned phosphorous-containing fertilizers, a nutrient that contributes to algae blooms and may contribute to the growth of aquatic invasive plants.
A number of landscaping programs are being implemented, and 100 percent of stormdrains within the Association have been marked "No Dumping, Keep Tahoe Blue." TKPOA was the first neighborhood in the basin at Lake Tahoe to achieve this.
The Association has also approved turf conversion & reduction.
Under the guidance of the Nonpoint Source Water Quality Management Plan, the Association has taken a multi-pronged approach to improving landscaping practices on Association property while also educating individual property owns on landscaping techniques and best management practices (BMPs).
Benefits of the NPS Plan:
Using both education and enforcement of HOA rules, the Association has an extensive array of tools to reduce runoff into the lagoons and lake from both Association-owned and privately owned property.
That means proper irrigation, proper fertilizing, better landscaping design and property management to keep water from running off the land into the lagoons and lake.
BMPs, a key tool in Lake Tahoe-wide efforts to improve Lake Tahoe clarity, are being installed on Association property according to Tahoe Regional Planning Agency standards, and many private property owners within the Association are installing them on their individual properties.
Eleven more properties were certified BMP compliant by TRPA in 2016.
To see what homeowners are doing to contribute, see the Take Action section below.
Tahoe Keys Property Owners Association has spent up to $400,000 a year harvesting the aquatic invasive plants just to keep the lagoons navigable for boat traffic, but the volume of weeds only continues to grow – now covering more than 90 percent of the Keys’ lagoons.
Individual property owners have volunteered to place bottom barrier mats around their docks to help fight the plants, but that barely scratches the surface of the 172-acres of lagoons and channels.
Guided by the Integrated Management Plan, the Association has been implementing a number of aquatic invasive plant control methods, and studied many more for possible future use.
First, the Association evaluated and modified the weed harvesting program – improving both harvesting and fragment control methods to make the existing methods work better than in the past.
Harvesting cuts up large swaths of aquatic invasive plants, leaving many fragments floating in the water. These plants can propagate by fragments, so fragment control is critical to reduce the spread of the weeds both inside and outside the Tahoe Keys.
After testing numerous fragment control methods in 2016, the Association is working to implement new tools and new techniques in 2017. A boat backup station has be placed in main channel in 2017 to reduce the fragments carried by boat propellers – a step above and beyond agency requirements.
In-the-water evaluations for larger-scale bottom barriers have begun, and diver-assisted hand pulling is tentatively planned over the next three years, contingent on funding.
In parallel, the Association has applied for a small-scale herbicide evaluation (less than 13 acres) in 2018 that would be followed by non-herbicide control methods, demonstrating the effectiveness of herbicides for an initial reduction of plant mass to a level controllable by other methods.
If the herbicide demonstration is permitted, the association would apply low levels of three herbicides found effective on the same plants in other regions, namely Endothall, Triclopyr and Penoxsulam, at nine test sites. The process would include an impermeable barrier between the lagoons and lake, monitoring, and numerous safety measures to ensure that these substances would not reach the Lake
The herbicides, approved by the Federal and California Environmental Protection Agencies, are nontoxic to humans, fish and wildlife, and would be diluted to between 0.02 and 2 parts per million, or about half the maximum concentrations allowed by the EPA. All of the herbicides break down by light, microbial action and other processes, typically degrading to non-detectable levels within a few days to two weeks.
Mechanical Harvesting & Fragment Collection
To date, this has been the main method of weed control in the Tahoe Keys – and it hasn’t been successful. The Tahoe Keys Property Owners Association has spent up to $400,000 a year on this method, only to see weeds increase in volume. But with new technology and methodologies, the association aims to reduce fragments created by harvesting that can spread and create new plants. These new techniques and equipment were tested and evaluated in summer 2016, and with the purchase of a new skimming boat, many improvements have been implemented in 2017 and already shown progress.
Bottom barriers, mats designed to smother aquatic invasive weeds, are currently being used in the Tahoe Keys. The Association is allowed a total of five acres of bottom barrier coverage (Tahoe Keys are 172 acres in water-covered area). While effective for small areas, they kill all plants, not just invasive weeds. Bottom barriers are useful for relatively small scale infestations and for individual property owners around their docks. In 2017, the Association placed the largest bottom barrier coverage to date.
By working with property owners to reduce runoff and use of fertilizers on land (the association has banned phosphorous-containing fertilizers), less nutrients will be introduced into the water that may contribute to weed growth. The Lake and Lagoon Friendly Landscaping Campaign, launched in 2016, aims to minimize these nutrients while also generally improving water quality. The association has also created a boat backup station and associated educational materials to reduce the spread of fragments that can create new infestations around the lake
Diver-Assisted Hand Pulling
Trained SCUBA divers can selectively target invasive plants, removing the majority of the plants from a treated area. Also most effective in smaller areas, diver-assisted removal may be useful in targeted locations. However, increased equipment support activities that interfere with navigation, diver safety, and turbidity can be negative aspects of these operations.
Laminar Flow Aeration
Air is bubbled up in a laminar flow from the bottom through the water column to bring proper oxygenation to the water closer to the bottom of the lagoons, which has been reduced by aquatic invasive plants. Trail aeration will evaluate benefits to the ecosystem and sediment.
UV light is a newly identified, still experimental method that may be found to help kill aquatic invasive weeds in the Tahoe Keys. There is a trial planned for Lakeside Marina, and the Association has pledged support for a small-scale test in the Tahoe Keys lagoons.
The association is evaluating the selective use of herbicides in the most impacted areas within the lagoons. When used properly by licensed applicators, herbicides are non-toxic to fish, wildlife and humans, only targeting the specific invasive plants. Although currently approved for use by the Environmental Protection Agency, the association would need permission from regional agencies (e.g., Lahontan Regional Water Quality Control Board) before implementing this control measure.
Herbicides being evaluated, along with proposed application concentrations:
Triclopyr: 1 part per million
Endothall: 2 parts per million
Penoxsulan: 5 parts per billion
The use of herbicides as part of an integrated plan has been endorsed by an array of independent national and regional experts, including Dr. Pat Akers with the California Department of Food and Agriculture, Dr. Joe DiTomaso of UC Davis, Dr. Kurt Getsinger with the U.S. Army Corps of Engineers, Dr. Sudeep Chandra with University of Nevada, Reno and Joel Trumbo with the California Department of Fish and Wildlife.
Other lakes and bodies of water have successfully used these herbicides to control aquatic invasive plants without harming native species or posing public health risks to drinking water supplies, including Discovery Bay south of the California Delta, Big Bear Lake in Southern California, Clear Lake in Northern California, Loomis Lake in Washington, and numerous areas within the Sacramento-San Joaquin Delta.
Comprehensive dye studies conducted in 2011 and again in 2016 were used to assess how herbicides would move in the lagoons during the trial period. The studies revealed that water movement within the lagoons is very limited, especially in the back lagoons where several of the proposed demonstration sites are located.
All of the herbicides break down by light, microbial action and other processes, typically degrading to non-detectable levels within a few days to two weeks.
Tahoe Keys West Lagoon Integrated Control Methods Test Application - Supporting Materials
What you can do
Join our Lake friendly Landscaping campaign this spring! Here’s how you (or your landscaper) can have a Lake Friendly Landscape that protects what we all love: our lagoons and lake!
Lake Friendly Landscaping is Easy.
Step 1: Don’t feed the weeds & clarity-killing algae with excess water run off - reduce your water use.
Saving water is a win-win-win. You save money, reduce runoff into the lake and lagoons and save water (we may have had a good winter, but that doesn't make up for four below average ones before it).
Other ways to save water & help our lagoons and lake:
Step 2: Don’t feed the weeds & clarity-killing algae with phosphorus fertilizer:
Use lake and lagoon friendly and TKPOA approved fertilizer types and applications (no phosphorus). Adding nutrients to the lake and lagoons only helps algae blooms and invasive weeds. The less we feed them, the better.
Follow these simple fertilizer rules:
How to read your fertilizer bag:
More great resources at Take Care Tahoe.
Contact the Association with any questions or concerns you have about Lake Friendly Landscaping and be sure to share this info with your contracted landscaping company!
BMPs in the Tahoe Keys
Best Management Practices, commonly known as BMPs, are a diverse set of methods required by Tahoe Regional Planning Agency to prevent sediments and pollutants from entering ground and surface water in the Lake Tahoe Basin.
For many property owners, this sounds scary – the TRPA handbook on BMPs is 736 pages long! Thankfully, here in the Tahoe Keys, BMPs are pretty simple. Your property may already be compliant, just waiting for a certificate.
First off, many issues, like steep slopes for example, don’t apply in the Tahoe Keys. Additionally, water is slow to infiltrate into the soil in the Tahoe Keys, and the water table is relatively high. These factors limit the range and scope of BMPs that apply to Tahoe Keys properties.
The Tahoe Keys are considered a high priority for BMPs by TRPA, Tahoe Resource Conservation District and the City of South Lake Tahoe. Most properties are in close proximity to water and the lack of BMPs could degrade water quality and increase aquatic invasive plants in the Tahoe Keys Lagoons.
Here’s where you come in.
TRPA recommends using Source Control BMPs for single-family properties. The purpose of Source Control BMPs is to prevent soil erosion. That boils down to:
1) Have a paved driveway
That’s it! Many single family properties in the Tahoe Keys already meet these requirements, yet don’t have a BMP Source Control Certificate – so getting a certificate could be as simple as making a phone call and getting an inspection. Find out more at www.tahoebmp.org.
But if your property already meets these requirements, why bother with getting the certificate?
So what do you do?
First, call the TRPA (775-589-5202) for an inspection. If you pass, you get your certificate! If not, TRPA staff person will recommend steps to make your property compliant, after which you can get another inspection for certification. TRPA staff don't need you to be at home; they just need access to the outside of your property. Both inspection and certification are currently free for single-family homeowners.
That’s all it takes! Please help the lake, help the environment, help the Tahoe Keys and help your property by taking these simple steps.
Boat Backup Station
We need your help to stop the spread of aquatic invasive plants. Follow these steps to remove plant fragments from your boat:
Tahoe Keys Boat Backup Station
August Algae Bloom
Attention Property Owners, Residents and Visitors
Dear Tahoe Keys Property Owners Association member,
An algae bloom in the west channel was reported August 15, 2017 at which point TKPOA contacted the appropriate authorities, including Lahontan Regional Water Quality Control Board (LRWQCB).
Both TKPOA and LRWQCB’s testing returned similar results, showing low-levels of toxins that warrant precautionary measures by TKPOA, Tahoe Keys property owners, residents and visitors.
Based on those results, LRWQCB is recommending the placement of caution signs around the Tahoe Keys (above) and regular monitoring of the bloom.
TKPOA has set out on a monitoring plan working with LRWQCB and the State Water Resources Control Board, US EPA and Tahoe Regional Planning Agency to develop next steps. This does not effect Tahoe Keys tap water or drinking water.
While the cause of the bloom has not yet been determined, the most likely scenario is a combination of increased nutrients introduced into Lake Tahoe and the Keys by high runoff levels from the region’s record-breaking winter along with increased water temperatures.
As noted in Tahoe Environmental Research Center’s State of the Lake Report, Lake Tahoe has warmed 10 times faster than normal over the last four years, driving algae growth elsewhere in Lake Tahoe. Likewise, dozens of similar blooms have been reported throughout the state this year due to similar conditions in other freshwater bodies. Learn more here: www.waterboards.ca.gov/water_issues/programs/swamp/freshwater_cyanobacteria.shtml
While TKPOA landscaping is not thought to be responsible for the bloom, all property owners can help reduce nutrients introduced into the lagoons by following TKPOA’s Lake and Lagoon Friendly Landscaping guide and installing BMPs, learn more here: www.keysweedsmanagement.org/#take-action
A: For the purposes of the Integrated Management Plan and Nonpoint Source Water Quality Management Plan, the Tahoe Keys is a development complex, which includes seven primary private and public landowner groups. This includes a nonprofit residential association (Tahoe Keys Property Owners Association) comprised of 1,529 homes and townhomes, a commercial marina, a medium sized commercial business center, a nonprofit dock and boat moorage association, the privately owned Lake Tallac and the nonprofit California Tahoe Conservancy.
Q: What is the Tahoe Keys Property Owners Association?
A: The Tahoe Keys Property Owners Association (TKPOA) is a private community connected by 11 miles (172 acres) of interconnected waterways. The Tahoe Keys is located at the southern tip
of Lake Tahoe in South Lake Tahoe, California. Most of the 1,500+ members who own homes, townhouses or vacant lots have a private boat dock and are located on its lagoons.
Q: What are the aquatic invasive plants in Tahoe Keys, and why are they a problem?
A: Aquatic invasive species including Eurasian watermilfoil and curly leaf pondweed, along with the native nuisance plant coontail, make up the bulk of the problem in the Tahoe Keys. They interfere with native species, harbor non-native fish species, create mosquito habitat and interfere with boating and other recreation.
Q: How did these plants get into the Tahoe Keys? Where did they come from?
A: Both invasive species are native to Europe and Asia, with Eurasian watermilfoil likely being introduced in the 1980s - curly leaf pondweed some time after that (first recorded in the Tahoe Keys in 2003). No one knows how they were introduced, but it is likely from home aquarium dumping or transported via boat.
Q: What are you doing now to fight the weeds?
A: Currently, the Tahoe Keys Property Owners Association is harvesting, using five harvester boats to cut as much weed mass as possible, spending as much as $400,000 a year. Despite these efforts, the volume of weeds is only increasing (The volume of weeds grew from 100 cubic yards in 1984 to 18,600 cubic yards in 2014). TKPOA has also entered the pilot phase of bottom barrier use, which is being expanded on with the proposed Integrated Management Plan (IMP).
In 2016, the Association has begun to improve on harvesting techniques and technology, including fragment collection to reduce the weeds' spread, plan a more robust bottom barrier mat program, and field a number of studies or test runs, as detailed in the plan section above.
In 2017, the Association has further improved harvesting, purchased an Omnicat skimmer boat to improve fragment collection, and implemented a boat backup station that is reducing the transport of fragments.
Q: How are environmental and regulatory organizations involved in this process?
A: We have been engaging local and regional agencies and stakeholder groups throughout the process for more than five years now, keeping them apprised of the planning process, jointly performing studies, and investigating proposed methods of weed management. Ultimately, the Plan will need to be approved by the Lahontan Regional Water Quality Control Board.
Q: How do we know using herbicides will be safe for the lake, other species and drinking water?
A: Extensive dye studies have been conducted in the Keys to determine water movement in different seasons, informing potential strategies for herbicide application. Because the herbicides break down rapidly in open waters (a matter of days), they become inert quickly and will not spread beyond the intended target locations in the Tahoe Keys. The herbicides under consideration are designed to become inert quickly and are specific to the problem plants found in the Tahoe Keys. These same herbicides have been proven to be effective elsewhere in California, in alpine lakes, and in other similar settings throughout the country.
Further study of herbicides are being considered for 2016, with a possible demonstration test application in 2018, if approved by permitting agencies.
Q: Why is the Tahoe Keys Property Owners Association preparing the Plan?
A: TKPOA has been investigating long-term solutions to the weed problem since 2007. The severity and cost of the weed problems in the Tahoe Keys, combined with TKPOA’s support of regional efforts to maintain and improve the quality of the Tahoe Keys and Lake Tahoe for its members, along with the predominately private land ownership of the Tahoe Keys, prompted TKPOA in 2012 to begin preparing a Plan in cooperation with numerous public agencies, interest groups and other landowners. In 2014, the Lahontan Regional Water Quality Control Board made the Plan a formal requirement.
Q: Can the Tahoe Keys just use bottom barriers to eliminate the problem?
A: Plants can easily grow on the barriers unless they are cleaned or removed and replaced every year. Experiments testing the barriers in the Tahoe Keys also showed that watermilfoil begins to inhabit the sediment that deposits over time on the bottom barriers. And curlyleaf pondweed does not require roots to grow, reproduce, or expand, thereby making bottom barriers of limited effectiveness for the highest threat invasive plant. A significant portion of the lagoons cannot be treated with barriers effectively due to the presence of hundreds of structures like docks, pilings and platforms (divers would have to work the barrier mats around these obstructions in turbid water). From a practical standpoint, widespread use of bottom barriers is not effective due to boat traffic that dislodges bottom barriers, which then become a safety hazard. For these and other reasons it has been estimated that complete coverage of the Tahoe Keys with bottom barriers, including placement, maintenance and removal, would cost more than $40 million.
Q: Can the Tahoe Keys be drained to eliminate the problem?
A: Realistically, no, due to a combination of variable waterway depths, structural threats to bulkheads, local groundwater conditions, seed bank of invasive species present in the sediments evolved to tolerate drought, the amount of energy/pumping required, and the need to filter, treat and dispose of the aquatic animals/plants/waters drained from the waterways. From a groundwater perspective, because the Tahoe Keys lands are built on highly porous materials (sand), draining the waterways is likely not possible. With the environmental impacts, prohibitive costs, problematic groundwater conditions, extensive seed bank in the sediments, and economic/recreation impacts of this method, draining is considered infeasible. Again, for curlyleaf pondweed, turions have evolved to survive extended drought periods and would come back even after drying the lagoons.
Q: Have herbicides been used in similar lakes or bodies of water?
A: First, it’s important to be clear that the herbicides will not be used in Lake Tahoe, they will be limited to the Tahoe Keys Lagoons. These lagoons are similar in bathymetry (underwater equivalent to topography), ecosystem function, habitat, depth, temperature and water quality to hundreds of similar shallow, warm water lakes in California. In addition, the lagoons are connected to Lake Tahoe by two channels. The herbicides can be controlled and prevented from entering Lake Tahoe.
Herbicides have been and are currently being used in many California water bodies, including Clear Lake, Big Bear Lake, Discovery Bay, and the Sacramento-San Joaquin Delta in California, as well as lakes in Washington, Oregon, Minnesota and Florida.
Q: What risks do these herbicides pose to the natural environment and humans?
A: Aquatic herbicides control aquatic vegetation without posing significant threat to fish, and have been approved for aquatic systems after extensive studies for efficacy and toxicology. These herbicides are regulated by the US Environmental Protection Agency and California EPA. They were required to be tested for potential harm to human health and the environment, and deemed as non-toxic to fish and humans when applied at proper concentrations by licensed applicators. because their modes of action affect plant processes like photosynthesis. The herbicides are not classified as carcinogens. They have been studied in the lab and in the field to find out what happens to their active ingredients in water, plants, fish and soil.
Each of the herbicides under consideration for the Tahoe Keys has been rated for fishing, recreation, livestock and pet consumption as: No restriction. Because herbicides are broken down by microbial action, photolysis and hydrolysis, they have half-lives from a few days to a few weeks.
Q: How will you prevent herbicides from getting into Lake Tahoe and potentially into drinking water?
A: A Rhodamine WT dye study analyzed the movement of water in the Tahoe Keys in different seasons, modeling the potential spread of herbicides from application sites over time. Applications will be made at times and locations that preclude movement from the Tahoe Keys lagoons to Lake Tahoe. Impermeable barriers will be used at some sites to prevent dissipation. Pre- and post-application water sampling and analysis will occur with each application. Because herbicides are broken down by microbial action, photolysis, hydrolysis, they have half-lives from a few days to a few weeks. So, as shown by the dye studies, by the time the herbicides could move out of a selected lagoon, they will have broken down to an inert state.
Q: Would the use of herbicides in the plan, if approved, open the door to herbicide use elsewhere in Lake Tahoe?
A: No, a permit for herbicide use in the Tahoe Keys could not be used for herbicide use anywhere else in Lake Tahoe. The TKPOA is not promoting use of herbicides in Lake Tahoe.
Tahoe Keys is a unique situation within the Lake Tahoe region: the lagoons are shallow and narrow, the weed problem is severe (and thus the control measures are needed) and it is physically isolated from the lake except for two small connecting channels (which make herbicides much easier to control than elsewhere). Any future weed management plan proposing the use of herbicides would have to undergo rigorous environmental review and permitting.
While the final plan to address invasive species in the Keys remains to be seen and fully considered, we applaud these property owners for starting this critically important process to address the issue. Doing nothing is not an option. The negative impact invasive species can have at Tahoe is clear, and history shows we can tackle the problem working together." - Joanne Marchetta, executive director, Tahoe Regional Planning Agency in a My Shot column in Moonshine Ink.
"I want to publicly applaud the [Tahoe Keys Property Owners Association].” - Shelley Aldean, TRPA Board Member in the Tahoe Daily Tribune.