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Pomparaug Watershed group urges aggressive effort to eradicate European water chestnut in Southbury lakes
Summary
Pomparaug River Watershed Coalition described rapid spread of invasive European water chestnut centered at Lake Stibbs, outlined manual and chemical control strategies, reported thousands of pounds removed by volunteers and small grants secured, and invited residents to volunteer for weekly pulls.
The Pomparaug River Watershed Coalition told the Southbury Board of Selectmen on July 6 that European water chestnut is a fast-spreading invasive plant threatening recreation and water quality in Southbury’s lakes and streams, and that early, aggressive action may allow local eradication.
Olivia DePalma, Watershed Programs Manager for the Pomparaug River Watershed Coalition, discussed the plant’s ecology, its arrival in Connecticut in the 1990s and its recent appearance in the Pomparaug watershed (first detected in Lake Stibbs in 2016). She said Lake Stibbs (described in the presentation as a roughly 12-acre water body owned by the Southbury Training School) has been the epicenter of local infestation and that seeds and fragments have spread downstream into Transylvania Brook, the Pomparaug River and Lake Zor.
DePalma described three primary management tools the coalition uses: hand-pulling from kayaks (volunteer-driven), targeted herbicide treatment (typically ClearCast, used selectively and under state rules), and mechanical harvesters (effective but costly). She said the coalition obtained a Connecticut DEEP aquatic-invasive-species grant that provided $4,000 for herbicide treatment at Lake Stibbs and also a grant from the Southbury Community Trust Fund to support tracking and removal.
DePalma reported near-term removal metrics: in 2024 the coalition ran multiple programs and reported pulling almost 4,000 pounds in four events; after expanding earlier in the season they later reported close to 10,000 pounds in a subsequent season of five programs. For the current (2026) season she said volunteers have removed about 6,400 pounds so far and the coalition aims to exceed 10,000 pounds. DePalma said the Lake Stibbs patch that was cleared remained clear this season and emphasized that early action increases the likelihood of eradication.
Board members asked operational questions: whether harvesters can be rented (DePalma said some companies and utility customers may lend or rent equipment), whether seeds are a skin irritant (she said they can poke when mature; volunteers are provided gloves), and whether eradication is realistic (DePalma said aggressive early intervention combining methods offers a real chance at eradication in this watershed).
How to help: DePalma invited volunteers to weekly Thursday pulls at Lake Stibbs (1600 South Britton Road, Southbury); the coalition provides kayaks, paddles and life vests and asks volunteers to register through its website. DePalma referenced the coalition’s website (pomparaug.org) and provided a contact phone number for volunteer arrangements.
Why it matters: Left unchecked, water chestnut forms dense surface mats that crowd out native plants, impede boating and fishing, and contribute to algal blooms when the plants die back; local eradication now would avoid years of costly management.
What’s next: the coalition will continue monitoring and removal through the summer, pursue grants and partnerships for mechanical harvesting where feasible, and keep the town informed of volunteer opportunities and treatment plans.
