In summer 2026, the Halifax Regional Municipality and the Centre for Water Resources Studies (CWRS) at Dalhousie University are testing floating treatment wetlands at Little Kearney Lake, Kearney Lake and the Halifax Public Gardens. Because there is significant development planned and underway in the Kearney Run watershed, which includes Kearney Lake, floating treatment wetlands have been proposed as a potential strategy for managing water quality.
The project was approved by Regional Council in August 2022, It was then expanded to the Public Gardens because Park managers have been dealing with an increase in aquatic plant growth in the park’s ponds, likely caused by excessive nutrients in the water.
Water quality concerns related to excessive nutrients have been managed using floating treatment wetlands elsewhere. This floating wetlands project is testing different module designs at Kearney Lake and the ponds in the Public Gardens to assess their effectiveness for use at additional sites in the future.
What are floating treatment wetlands?
Floating treatment wetlands were first developed to manage nutrient concentrations in wastewater treatment lagoons. These floating, modular frames are planted with water-loving and wetland plants. Seeking nutrients, these plants extend their roots down through the bottom of the frames into the water below. Once the module is too crowded with plants, some are removed from the system and composted elsewhere, permanently removing excess nutrients from the water system. Some plants are left behind to continue cleaning up nutrients and the cycle begins again.
This technique has been successfully used for nutrient removal in freshwater bodies in other North American cities. However, this project is the first time floating treatment wetlands have been tested in a colder climate like the Halifax Region. . Researchers at the CWRS are testing which plant species grow best in the modules, how effective the floating wetlands are at reducing water quality impacts and the level of maintenance required to keep the modules in working condition.
Where are the impacts coming from?
The results of our LakeWatchers water quality monitoring program show lakes in the municipality are affected by widespread surface hardening. This process, where land previously covered in soil and plants is paved or hardened so water can’t get through, diverts stormwater into the nearest surface water.
When surfaces are hardened, by pavement, stone, concrete or very compacted soil, water cannot soak through easily. Instead, it flows over the surface, picking up whatever contaminants it encounters, like plastic from tires and litter, hydrocarbons from oil and gasoline, nutrients from soil and debris and chloride from road salt. When the run-off discharges into waterbodies, it can negatively impact water quality, threatening recreational uses like swimming and damaging the health of wildlife habitat.
In a healthy system, some water soaks into the soil, and some is taken up (along with nutrients and other contaminants) by plants. The water that soaks into the soil eventually sinks deep into the earth, refilling aquifers essential for drinking water and discharging into wetlands, rivers and lakes. By the time it reaches surface waterbodies, the water has been filtered, and many chemical compounds like nutrients from organic material and fertilizer, chloride from road salt, and other contaminants, have been removed.
What should I expect to see?
In August 2025, thirty-five wetland modules were planted and installed in Little Kearney Lake, a marsh upstream from Kearney Lake. These were left in place over winter to monitor whether plants survived and if the module frames withstood winter freeze.
In late June 2026, these modules will be moved into Kearney Lake and roughly 25 more will be installed. All modules will be planted with wetland and water-loving plants. To assess their success at removing nutrients, containing sediment, producing plant biomass and providing shade and water temperature reductions for fish, they will be monitored by CWRS researchers, who will be supported by staff at Maskwa Canoe Club.
Five wetland modules will be deployed in the ponds at the Halifax Public Gardens this summer. They will be monitored by CWRS researchers and Public Garden staff to assess whether this technique is viable in a more sheltered environment.
Once the project is complete, municipal staff will share the results and recommend the next steps based on the performance of the modules.