Swan Lake Water Quality

Swan Lake was formerly a gravel pit in the 1960s and 1970s and is now a valued community feature, surrounded by parks, trails and urban development near the heart of Historic Markham Village.

In late 2010, residents of Swan Lake Community raised concerns about the water quality in Swan Lake. In response, the City initiated a monitoring program of the lake as well as upstream stormwater management ponds. High levels of phosphorus in the lake water and sediment were found to be contributing to low oxygen levels in the water, degraded fish habitat and the growth of blue-green algae.

Council authorized an innovative treatment to help improve the lake water quality in 2013, adopting the same technology used in Glasgow’s Strathclyde Lochfor the 2014 Commonwealth Games.

In the summer of 2013, 25 tonnes of Phoslock – a non-toxic clay product capable of removing phosphorus from the water and capping phosphorus in the bottom sediment - was applied across the lake.

Swan Lake Phoslock Treatment Continued monitoring of the lake water quality has indicated a 60% reduction in total phosphorus in surface and mid layers of the lake and increased water clarity in 2014. While phosphorus levels remain relatively high in the system, the risk of algae blooms and the severity of impacts have been reduced through the adoption of this innovative treatment technology.

For more details see the article in the Phoslock Newsletter, Autumn 2014. [PDF]