Saint Lawrence River

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The Saint Lawrence River is a large river in North America. It is the primary drainage of the Great Lakes into the Atlantic Ocean. The river flows through the provinces of Ontario and Quebec, forming part of the Canada-United States border between Ontario and the New York State.


The Saint Lawrence River originates at the outflow of Lake Ontario between Kingston, Ontario on the north bank and Cape Vincent, New York on the south. From there, it flows through the Thousand Islands and then the Hochelaga Archipelago, which includes the island of Montreal. At Montreal, the river widens, to form Lake Saint Louis and then narrows again at the Lachine Rapids.

Further downstream, the river passes the provincial capital of Quebec City before draining into the Gulf of Saint Lawrence, the largest estuary in the world.

Distance, draining & discharge

The Saint Lawrence River flows 1,197 kilometres (744 miles) from its outflow at the eastern end of Lake Ontario to the Gulf of Saint Lawrence. If calculated from its furthest headwater—the North River in the Mesabi Range in Minnesota—the distance is a much-longer 3,058 kilometres (1,900 miles).

Its drainage area includes the Great Lakes, the world's largest system of fresh water lakes, and has a size of 1.03 million square kilometres (390,000 square miles). The average discharge at the mouth is 10,400 cubic metres per second (367,000 cubic feet per second).

Major tributaries

Lake Champlain and the Ottawa, Richelieu, and Saguenay rivers drain into the St. Lawrence.


The Saint Lawrence River was thought to be relatively safe from pollution, but by the end of the 1970s, despite its volume flow, the river was no longer effective at diluting wastewater discharged into it. The river became so polluted that fewer recreational activities were being carried out there and fish species were seriously threatened. [1]

As of 2005, Montreal was discharging a total of 900 billion litres of sewage into the annually. While most received minimal primary treatment, 3.6 billion litres entered the river as raw sewage. [2]

Industrial pollution and the former use of banned pesticide DDT along the Great Lakes, St. Lawrence River and its tributaries have had a serious impact on the river's Beluga whales. [3][4]


The Thousand Islands region is a popular recreational area.


Many beaches along the St. Lawrence have had to be closed due to pollution, although the efforts are underway to improve water quality and some beaches have been re-opened. In the Montreal region, clean-up measures have improved the water quality at some sites, but problems with bacterial contamination persist, especially downstream.[5]

Lachine Rapids

While the Lachine Rapids make boating hazardous, they also provide a venue for white water rafting, kayaking and even river surfing. A standing wave adjacent to the Habitat 67 housing complex has become a well known surf spot.[6]


  1. Ministère du Développement durable, de l’Environnement et des Parcs (HTML). Quebec Government Web site. Retrieved on 2008-02-03.
  2. MacQueen, Ken. Canada Dumping Raw Sewage into Its Waterways, Maclean's Magazine, The Canadian Encyclopedia, 2005-10-17. Retrieved on 2008-02-06.
  3. Shabecoff, Philip. Pollution Is Blamed for Killing Whales in St. Lawrence, New York Times, 1988-01-12. Retrieved on 2008-02-06.
  4. Pollution stunts Canada's beluga whales, Agence France Presse, 2007-09-02. Retrieved on 2008-02-06.
  5. Potential Swimming Sites in the St. Lawrence River. Environment Canada (2007-07-11). Retrieved on 2008-02-06.
  6. Woodley, Matthew. Surf’s up in the St. Lawrence, Montreal Mirror, 2005-06-09. Retrieved on 2008-02-06.