System at a Glance
Lake Ontario — Current Level
Well below 2017 record high
Watershed Indicators — Toronto Area Rivers
Water Treatment Plants — Four Facilities
Infrastructure Context
R.C. Harris — the most beautiful waterworks in the world
The R.C. Harris Water Treatment Plant, opened in 1941 after a decade of construction through the Depression, is widely regarded as one of the finest examples of Art Deco public architecture in Canada. Its marble interiors, terrazzo floors, and lakefront setting led writer Michael Ondaatje to call it "the Palace of Purification" in his novel In the Skin of a Lion.
Harris was controversial in its time — critics argued that a water treatment plant didn't need marble floors during the Depression. The city's commissioner of works, Rowland Caldwell Harris, disagreed: he believed public infrastructure should be beautiful, durable, and built to last centuries.
At 85 years old, R.C. Harris is a designated heritage building still treating 950 ML/day — almost exactly as designed. It is one of the few civic infrastructure buildings in Canada where the architecture is as significant as the engineering.
Lake Ontario — unlimited supply, managed internationally
Lake Ontario contains approximately 1,640 km³ of water — effectively unlimited supply for Toronto's purposes. Toronto Water's constraint is treatment capacity and distribution infrastructure, not source volume.
Lake levels are managed by the International Joint Commission under Plan 2014, which balances the interests of 8 million people who live along Lake Ontario and the St. Lawrence River — recreational users, shoreline property owners, commercial navigation, hydropower, and municipal water supply.
The lake is currently above its long-term average at 75.37 m IGLD 1985. The 2017 record high (75.88 m) caused significant shoreline flooding across the Great Lakes region and prompted review of the IJC regulation plan.
Toronto Water System Map
Full Water Cycle