Floating Wetland Islands: A Sustainable Solution for Lake Management

Nick Decker, PA State Parks Resource Manager, and Cory Speroff and Katie Walston of Princeton Hydro position a floating island of native plants in the lake at Frances Slocum State Park

Looking for a unique and creative way to manage nutrient runoff in freshwater lakes? Installing Floating Wetland Islands (FWI) is a low-cost, effective green infrastructure solution used to mitigate phosporus and nitrogen stormwater pollution often emanating from highly developed communities and/or argricultural lands.

FWIs are designed to mimic natural wetlands in a sustainable, efficient, and powerful way. They improve water quality by assimilating and removing excess nutrients that could fuel algae growth; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments.

“A pound of phosphorus can produce 1,100 lbs of algae each year. And, each 250-square foot island can remove 10 lbs of phosphorus annually.” explains Princeton Hydro Staff Scientist Katie Walston. “So, that’s 11,000 lbs of algae that is mitigated each year from each 250 square foot of FWI installed!”

This illustration, created by Staff Scientist Ivy Babson, conveys the functionality of a Floating Wetland Island

This illustration, created by Staff Scientist Ivy Babson, conveys the functionality of a Floating Wetland Island

Typically, FWIs consist of a constructed floating mat with vegetation planted directly into the material. Once the islands are anchored in the lake, the plants thrive and grow, extending their root systems through the mat and absorbing and removing excess nutrients from the water column such as phosphorus and nitrogen.

Native plants on the floating island designed by Princeton Hydro that will help reduce the phosphers and algae in the lake at Frances Slocum State ParkThe plants uptake a lot of nutrients, but the workhorse of the FWIs is the microbial community. The matrix used within the islands has a very high surface area and it promotes microbial growth, which performs the majority of the nutrient uptake. Additionally, the root growth from the plants continues to increase the surface area for the microbial biofilm to grow on. Both the plants and microbes acting together help optimize nutrient removal.

Princeton Hydro has designed and installed numerous FWIs in waterbodies large and small for the purpose of harmful algal bloom control, fisheries enhancement, stormwater management, shoreline preservation, wastewater treatment, and more. FWIs are also highly adaptable and can be sized, configured, and planted to fit the needs of nearly any lake, pond, or reservoir.

Greenwood Lake

Recently, the Princeton Hydro team completed a FWI installation in Belcher’s Creek, the main tributary of Greenwood Lake. The lake, a 1,920-acre waterbody located in  both Passaic County, New Jersey and Orange County, New York, is a highly valued ecological and recreational resource for both states and has a substantial impact on the local economies. In addition, the lake serves as a headwater supply of potable water that flows to the Monksville Reservoir and eventually into the Wanaque Reservoir, where it supplies over 3 million people and thousands of businesses with drinking water. 

Since the lake was negatively impacted by HABs during the 2019 summer season, Greenwood Lake Commission (GWLC) has made a stronger effort to eliminate HABs and any factors that contribute to cyanobacteria blooms for 2020 and into the future. Factors being addressed include pollutant loading in the watershed, especially that of Belcher’s Creek. The installation of FWIs in Belcher’s Creek will immediately address nutrients in the water before it enters Greenwood Lake and help decrease total phosphorus loading. In turn this will help reduce HABs, improve water quality throughout the Greenwood Lake watershed, and create important habitat for beneficial aquatic, insect, bird and wildlife species.

“In addition to the direct environmental benefits of FWIs, the planting events themselves, which involve individuals from the local lake communities, have long-lasting positive impacts,” said Dr. Jack Szczepanski, Princeton Hydro Senior Project Manager, Aquatics Resources. “When community members come together to help plant FWIs, it gives them a deepened sense of ownership and strengthens their connection to the lake. This, in turn, encourages continued stewardship of the watershed and creates a broader awareness of how human behaviors impact the lake and its water quality. And, real water quality improvements begin at the watershed level with how people treat their land.”

The project was partially funded by the New Jersey Department of Environmental Protection’s (NJDEP) Water Quality Restoration Grants for Nonpoint Source Pollution Program under Section 319(h) of the federal Clean Water Act. As part of the statewide HAB response strategy, the NJDEP made $13.5 million in funding available for local projects that improve water quality and help prevent, mitigate and manage HABs in the state’s lakes and ponds. The GWLC was awarded one of the NJDEPs matching grants, which provided $2 in funding for every $1 invested by the grant applicant. For this project, the GWLC purchased the FWIs and NJDEP provided the 2:1 cash match in order for the GWLC to implement additional HAB prevention and mitigation strategies in critical locations throughout the watershed.

Check out the photos from last month’s installation:

Here are a few more examples of FWI design and installation projects we’ve completed:

Frances Slocum Lake

Officials with the state Department of Conservation and Natural Resources, Luzerne Conservation District, Nanticoke Conservation Club, and students at Rock Solid Academy in Shavertown teamed up with Princeton Hydro to install two floating islands on the lake. They were planted natives to the area, including Green Bulrush, Broadleaf Arrowhead, Blue Flag Iris, Shallow Sedge, and Spotted Joe-Pye.

Princeton Hydro also installed solar-powered aeration systems in the middle of the FWIs. Aeration systems provide additional water quality improvements, help prevent water around the islands from stratifying, promotes “through-column” mixing, and helps to minimize the occurrence of phytoplankton blooms. The use of solar-powered aeration, whether installed on a FWI or along the shoreline, creates a sustainable, cost-effective, zero-energy water treatment solution, and eliminates the need to run direct-wired electrical lines to remote locations. Learn more.

Princeton Hydro also installs solar-powered aeration systems on FWIs, creating a sustainable, cost-effective, holistic water treatment solution.
Harveys Lake

Princeton Hydro, along with project partners, installed five floating wetland islands in Harveys Lake in order to assimilate and reduce nutrients already in the lake. The islands were placed in areas with high concentrations of nutrients, placed 50 feet from the shoreline and tethered in place with steel cables and anchored. A 250-square-foot FWI is estimated to remove up to 10 pounds of nutrients per year, which is significant when it comes to algae. Learn more.

Volunteers install native plants in one of the FWIs installed in Harveys Lake. Photo by: Mark Moran, The Citizen’s Voice.
lake hopatcong

Through a nonpoint source pollution grant awarded by NJDEP to the Lake Hopatcong Commission, Jefferson Township was able to install FWIs in order to deliver better water quality to Ashley Cove and Lake Hopatcong. The primary goal of the project was to reduce high levels of algae-causing phosphorus present in the lake. In each FWI, indigenous plants, Milkweed and Hibiscus, among other vegetation, were planted along with peat and mulch. Learn more.

Casey Hurt, right, and Richard Ampomah maneuver one of two floating wetland islands in Ashley Cove.
Lake Holiday

Two interconnected sets of FWIs were installed in Lake Holiday in the tributary coves of Isaac’s and Yeider’s Creeks. The strategic placement of the islands eliminates interference with normal boat traffic. In order to minimize movement, the FWIs were secured to trees along the bank with coated cable and protective bands and anchored to the lake bottom with submerged concrete blocks. Learn more.

Senior Scientist Katie Walston installs goose netting around the vegetation in order to prevent geese and other unwanted species from feeding on the plants.

Over the coming weeks, our team will be in Asbury Park, New Jersey installing FWIs in Sunset Lake. Stay tuned for more! For additional information about floating wetland islands and water quality management, go here: bit.ly/pondlake.

Washington Post’s Climate Story Features Princeton Hydro

Photo credit: The Washington Post

Did you know that New Jersey is one of the fastest-warming states in the nation? Not only that, did you know the average temperature increase in the state is double the average of the rest of the Lower 48 states?

In a recent article, the Washington Post uncovers quite startling findings from analysis of more than a century of National Oceanic and Atmospheric Administration temperature data across the Lower 48 states and 3,107 counties. The article takes a specific look at the impacts climate change has had on Lake Hopatcong.

Princeton Hydro has been working with Lake Hopatcong for 30+ years, restoring the lake, managing the watershed, reducing pollutant loading, and addressing invasive aquatic plants and nuisance algae bloomsLake Hopatcong has one of the longest, continuous, long-term ecological databases in New Jersey; 30+ years of consistently collected water quality data.

Dr. Fred Lubnow, Director of Aquatic Programs, and Katie Walston, Senior Scientist, are featured in the Washington Post article. Here’s an excerpt:

On a cool but sunny day in May, Fred Lubnow, director of aquatic programs at Princeton Hydro, and Katie Walston, a senior scientist there, pulled up their anchor in Lake Hopatcong to find it covered with aquatic weeds. The culprit? Fertilizer runoff combined with winters too warm to kill them off.

“The plants start growing earlier and linger around longer, as well,” Lubnow said. The thick ice blocked sunlight from nurturing the weeds. But “in some of these shallow areas, as early as February, we’re looking through the ice seeing the plants growing.”

By summer, the weeds become a nuisance, forcing the state government to “harvest” them with large paddles and toss them onto a conveyor belt, then onto barges. Some years, funding has been hard to get, delaying harvesting and angering homeowners.

“If this area is not harvested, you can’t get a boat through it,” Lubnow says. Swimming isn’t possible, either. Fishing becomes difficult.

Get the full Washington Post story here!

If you’d like to read more about climate change, check out our recent blog:

Four Ways Climate Change Can Affect Your Lake