St. Lawrence River: overview

The St. Lawrence hydrographic system, including the Great Lakes, is one of the largest in the world. Its surface area of 1.6 million km2 is the third largest in North America, after the Mississippi and Mackenzie rivers. It drains more than 25% of the Earth's freshwater reserves and influences the environmental processes of the entire North American continent. Over 30 million Americans and 15 million Canadians live in this immense basin.

The St. Lawrence hydrographic system

The geographic position of the St. Lawrence and its physical characteristics make it a significant socio-economic asset for Quebec, Canada, and the industrial heartland of the United States. The St. Lawrence links the Atlantic Ocean with the Great Lakes and is among the world’s most important commercial waterways.

The St. Lawrence: A Rich and Majestic Ecosystem

The St. Lawrence harbours a complex ecosystem whose physical properties vary from upstream to downstream.It includes lakes and freshwater reaches, a long estuary, and a gulf with marine features. The area is home to richly diverse habitats and an equally rich diversity of flora and fauna.

Lake Saint-Pierre
Michel Arseneau, Environment Canada

Lake Saint-Pierre

The St. Lawrence is a priceless jewel of our natural heritage. It has sheltered four Ramsar sites (1971 Convention on Wetlands of International Importance) the largest of which is located in Lake Saint-Pierre (12000 ha). The same site also has the distinction of having been declared a World Biosphere Reserve in 2001.

The Saguenay-St. Lawrence Marine Park was created in 1998 through a joint federal-provincial initiative andit is part of the global network of marine conservation areas. Some sixty territories enjoy provincial or federal protection as migratory bird sanctuaries, ecological reserves, conservation parks, etc. The area encompasses more than 100,000 ha of wetlands on the Canadian shores of the Great Lakes-St. Lawrence Basin, with some 18,000 ha in the Lake Saint-Pierre region alone.

Under Environment and Climate change Canada’s Water Science and Technology Directorate, scientists are carrying out several monitoring and research projects on water quality and aquatic ecosystems. The mandate of these experts is to acquire more knowledge about the status of water as a resource in Canada and inform the general public and other involved in order to help in decision-making. Learn More…

St-Lawrence Plan

  • Fact sheets on indicators of the State of the St. Lawrence
    The fact sheets in this series report on the state of health of the St. Lawrence ecosystem based on environmental indicators and from a long-term perspective.
  • Overview of the State of the St. Lawrence River
    The overall health of the St. Lawrence River can be considered to be between intermediate and good. This picture emerges from the 2019 edition of the Global Portrait of the State of the St. Lawrence River recently released by partners of the St. Lawrence Plan.
Did You Know?

The hydrographic system of the St. Lawrence-Great Lakes stacks up worldwide!

  • It has the world’s 13th largest drainage basin, at 1610000 km2
  • It ranks 16th for its mean annual flow, 12600 m3/s just off Quebec City
  • It is the 17th longest, at 3260 km starting from Lake Superior to the Cabot Strait

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