The History of T.O.'s H2O

Kim Tait, associate curator of Mineralogy, and Mary Burridge, assistant curator of Ichthyology at the ROM

The waterways that surround and run through Toronto have shaped its past

The name Toronto likely derives from the Mohawk word Tkaronto, meaning “where there are trees standing in the water.”

For more than two centuries, an abundant supply of fresh water has fuelled Toronto’s growth and prosperity. The city’s many waterways have offered pleasurable places for recreation and abundant sources of fresh food, but they’ve also been the source of outbreaks of cholera and typhoid fever. In many ways, Toronto’s water has shaped the city we know today.

Toronto’s six waterways—the Etobicoke, Mimico, Humber, and Don rivers, Highland Creek, and the Rouge River—drain into Lake Ontario along 157 kilometres of constantly changing shoreline. The first settlements in the Toronto region, established by the Petun and Neutrals, were strategically located near the mouths of the Humber and the Rouge. When Europeans arrived, they followed the same pattern, building their settlements around water.

By 1834, when the city of York was incorporated as Toronto, there were 9,254 residents. As the population grew and became more concentrated, the availability of clean, safe drinking water and proper means for disposing of waste and sewage developed into issues. The dangers and consequences of unsanitary conditions were not immediately recognized— at great cost to public health.

In those early days, many small streams and creeks flowed through the city. Taddle Creek - which flowed from the Annex southeast through the University of Toronto lands before emptying into Lake Ontario—was one example. Local residences and breweries drew on it for their fresh water. But the creek was also used as a dumping ground for waste, and by 1830 people were reporting foul smells. The contamination of waterways such as Taddle Creek led to several cholera outbreaks in the city. In 1832, cholera claimed the lives of more than 200 residents and threatened the city’s economy. As a result, the York Board of Health was put in charge of guarding against future infectious diseases. But the city’s numerous waterways made it particularly vulnerable to epidemics of water-borne illnesses and the board was not able to prevent outbreaks of typhoid fever in 1845 and 1847 and of cholera in 1849, 1854, and 1866.

In the early 1860s, before unsanitary water was discovered to be the cause of the cholera outbreaks, Taddle Creek was dammed to create McCaul’s Pond, a long sinuous water feature on the University of Toronto campus. Students used it for fishing, skating, and swimming. But it, too, became increasingly polluted as more large buildings went up in the area, including the Toronto Baptist College (now occupied by the Royal Conservatory of Music). The increased waste in the Yorkville drains was discharged into the already-overwhelmed Taddle Creek and swept downstream to fester in McCaul’s Pond. Meanwhile in the Toronto Harbour there was so much sewage accumulation that it was interfering with the movement of cargo.

Clearly something had to be done. The city established the Water Works Commission and installed an infrastructure and piping system to draw the city’s water supply from the lake. In the early 1870s, the commission decided to move the intake pipe for the city’s water supply from the harbour to the lakeside of Toronto Island, and water was piped through a 3-kilometre wooden conduit, using the island’s sands as a natural filter. In 1881 the city enacted a bylaw that required citizens to abandon private wells and use the piped city supply.

As time went on, a series of broken pipes, more sewage dumping, and further typhoid epidemics led the city to experiment with and adopt chlorine disinfection as a sanitization method. Toronto became a North American leader in the use of this technology. It wasn’t until much later, due to the high cost, that Toronto got its first sewage-treatment facility, which uses physical, chemical, and biological processes for decontaminating water.

The Ice Ages

Over the last 2 million years, glaciers advanced and retreated through what is now Ontario, scouring and re-shaping the landscape. About 100,000 years ago, the last major event began, and ice eventually covered much of Canada. By 20,000 years ago, the ice sheet extended as far south as Ohio.

The basin of Lake Ontario had been scraped out by various glaciations, the last advancing southwest from its source in Labrador and Quebec. The climate slowly warmed again, and about 14,000 years ago the finger of ice across Lake Ontario began to melt and fill the basin. The lake would have filled only to the same depth as today had the water been able to drain out the St. Lawrence Valley into the ocean, but this passageway was still blocked by ice. The water rose to a level 45 metres higher than Lake Ontario is today before it could find an icefree outlet—into the Hudson River Valley.

This deep lake sitting in the Lake Ontario basin was called Lake Iroquois, and was much larger than today’s Lake Ontario. We know this because the prominent shore bluff it cut at its high  water mark is recorded in Toronto’s sedimentary deposits. Many remnants of the shoreline are familiar Toronto landmarks today.

One section can be found near Davenport Road and Spadina Avenue—where Casa Loma is perched on top of the bluff. Seven thousand years before the castle was built, the perch was a convenient lookout from which early paleo hunters spotted prey, such as caribou, mastodon, and mammoth.

In the east end, the Scarborough Bluffs are another landmark remnant of the ancient shoreline. The towering cliffs were the reason Elizabeth Simcoe named the area Scarborough in 1793, for their similarity to the cliffs of Scarborough, England.

At the same time, the area occupied by downtown Toronto today would have been under about 60 metres of water—the height of a 20-storey building. While southern Ontario and Quebec were glaciated, the weight of the ice, up to 2 kilometres thick, actually tilted the land so that it sloped down to the east. Because so much of the Earth’s water was locked up in glacial ice, sea level at the time was almost 100 metres below where it is today.

When the ice blocking the St. Lawrence outlet suddenly cleared about 12,000 years ago, it was like a plug being pulled from a bathtub, and Lake Iroquois abruptly drained. Sea levels were still low and huge quantities of fresh water were still locked up in ice to the northeast—so all the Great Lakes also drained, almost entirely.

As a result, Toronto’s rivers had to travel tens of kilometres further to reach the much smaller lake, now called Lake Ontario. To do so they energetically cut down through the glacial sediments left by the ice sheet and then through the lake-bottom sediments, carving a physical record of the event in what are now Toronto’s many ravines.

Low lake levels persisted until at least 8,000 years ago, when the eastward-sloping land began rapidly to tip back to its original horizontal plane as the weight of the glaciers lifted, a process called “glacio-eustatic rebound.” It is still occurring today, though at a much slower rate.

Taddle Creek

With its headwaters located in the Annex, Taddle Creek flowed through the area now occupied by Philosophers’ Walk behind the ROM, the Princess Margaret Hospital, the Hospital for Sick Children, and New City Hall towards the Eaton Centre, eventually to empty into Lake Ontario near Parliament Street and the Esplanade.

Toronto’s Changing Lakeshore

Over the years, Torontonians have re-shaped the city’s waterways for public health reasons and altered the shoreline of Lake Ontario to suit their needs. Early mapping indicates that Toronto’s original lakeshore lay between 50 and 150 metres south of present-day Front Street—somewhere underneath the current railway tracks. Since the mid-1850s, repeated waves of lake-filling have extended the land area to create more space for industry, port functions, recreation, condos, and the railway.

Between 1850 and 1870, Toronto was the centre of operations for Canada’s railways. There had been little space at the city’s southern edge to build Union Station and railway tracks, so the lake was radically filled in at the shoreline to create the needed space. And as commercial and industrial development intensified during the second half of the 19th century, the land area between Bathurst and Parliament streets was extended significantly by means of timber cribbing, which was set 3.4 metres down into the water and filled at first with sewage, municipal waste, dredgings from the harbour bottom, and material from construction sites; later fill contained derelict boats, the remains of wharf structures, and other abandoned material. Some of the most dramatic shoreline changes resulted from the filling in of Ashbridge’s Bay to create the Port Lands, the building of the 5-kilometre-long Leslie Spit, and in the 1970s the construction of the lakefill parks Ontario Place and Ashbridge’s Bay Park.

To simplify water delivery and fire protection throughout the city, in the mid-1870s the city constructed the Rosehill Reservoir just southeast of Yonge and St. Clair- on the crest of the ancient glacial Lake Iroquois shoreline. The reservoir was also a scenic addition. A footpath around the reservoir, affording excellent views of Lake Ontario and downtown Toronto, was frequented by well-to-do locals on their evening stroll.

By the 1940s it had become obvious that if the reservoir were covered, less chlorine would be needed to purify the water, maintenance could be reduced, and capacity could be increased. But no action was taken until the height of the Cuban missile crisis in 1962, when Canadian civil defence officials advised that radioactive contamination of the water from nuclear fallout would negatively affect human health—then the reservoir was quickly covered. The surface became a landscaped park with children’s playgrounds, reflecting ponds, and a fountain. Nine other inland subterranean lakes still masquerade as public parks in the city.

In 2010, environmental advocate Alexandra Cousteau, founder of Blue Legacy International, embarked on a 23,700-km journey across North America to investigate the state of this continent’s watersheds.

While in Toronto, Cousteau learned about conservation projects such as Bring Back the Don and Lake Ontario Waterkeeper as well as how Toronto deals with its waste. She also traced the underground watercourse of Mud Creek. Like Taddle Creek, it was contaminated by waste dumping in the 19th century and eventually buried in places along its route from Downsview Park to the Don River at Evergreen Brick Works.

Read more about Alexandra Cousteau’s Toronto visit and her thoughts and findings on the state of the world’s water in the next issue of ROM magazine.