For years, Dow’s Lake “wasn’t thought to be viable for swimming,” says Halsall. “But when you take a closer look, you have pristine water, these thriving ecosystems with trophy fish in abundance, plenty of species at-risk, protected turtles and birds that are living quite happily and quite successfully there.”
Looking across the water from the new dock near Queen Elizabeth Driveway and Lakeside Avenue, the white pines at the Dominion Arboretum whisper the history of the waterway. What used to be a pine-dotted cedar swamp was razed and flooded during the construction of the Rideau Canal. Over its almost 200-year history as part of the canal system, Dow’s Lake has been put to work. At Commissioner’s Park, where thousands of tulips now bloom each May, was a lumber yard a century ago, with a cannery nearby. When water levels dip in the spring and fall, the shallow parts of the lake sometimes reveal sections of an old causeway that used to bisect the waterway from 1904 to 1928.
Because of that history, and the city’s sewage overflow issues, many thought the water quality in Dow’s Lake was unsuitable for swimming, says Halsall. However, testing for the bacteria E. coli, a standard marker for water quality, throughout 2023, 2024 and 2025 indicated safe levels. The National Capital Commission also assessed human health risks, searching for other water contaminants from the lake’s industrial past, such as lead and cadmium. When those turned up clean, “that really greenlit the site,” says Halsall.