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St. Lawrence River

For Quebecers, the St. Lawrence River is the heart of Québec and thus of profound importance. It was the gateway through which the first European settlers arrived in North America and a source of their economic, social and cultural development in the centuries that followed. In sum, the St. Lawrence River shaped Québec as we know it today. The shores of the river and its tributaries are home to over 80% of Québec’s population, and 50% of Quebecers get their drinking water from these watercourses.


  • Overview of water quality
  • Bacteriological quality of the shoreline water
  • Modelling of the bacteriological quality of potential swimming sites
  • Toxic contamination in freshwater fish
  • Other publications


Photo : Fleuve Saint-LaurentOver time, the concentration of human settlements on the shores of the St. Lawrence River and its tributaries, coupled with substantial industrial and agricultural development, led to major environmental problems. At the beginning of the 20th century, the St. Lawrence was thought to be relatively safe from pollution, but by the end of the 1970s, despite its impressive flow, the river was no longer effective at diluting the wastewater discharged into it. The river had become so degraded that fewer and fewer recreational activities were being carried out there and a number of fish species were seriously threatened.

Faced with the accelerated degradation of the river’s water quality, the Québec government took immediate action by creating programs to curb the different sources of pollution diminishing the quality of the St. Lawrence and its tributaries.

Among others, in 1978 the Québec government set up a highly ambitious water treatment program (Programme d’assainissement des eaux du Québec) under the responsibility of the Ministère de l'Environnement. The program included three components: urban, agricultural and industrial wastewater treatment.

The efforts and initiatives undertaken by the Québec government and its socioeconomic partners since 1978 to clean up, conserve and protect the St. Lawrence River and its tributaries constitute unprecedented and key milestones in this regard. They paved the way for coordination and harmonization agreements between the governments of Canada and Québec, the first of which, the St. Lawrence Action Plan (SLAP), was signed in 1988. The SLAP was renewed in 1994 as St. Lawrence Vision 2000 and again on June 8, 1998, for another five years.


Overview and follow-up indicators on the state of the St. Lawrence River

On June 1, 2006, the governments of Canada and Québec announced the implementation of the St. Lawrence Plan For a Sustainable Development Phase IV – 2005-2010 that emerged from the most recent five-year cooperation agreement between the two levels of government. This agreement represented the continuation of preceding agreements that have governed Canada-Québec St. Lawrence River collaboration since 1988.

The Overview of the State of the St. Lawrence River 2008 was prepared as part of the State of the St. Lawrence Monitoring Program.

This overview, which shows that the St. Lawrence River current state of health is in the intermediate to good range, was prepared by five St. Lawrence Plan partners: the Ministère du Développement durable, de l’Environnement et des Parcs du Québec, Environment Canada, Fisheries and Oceans Canada, Stratégies Saint-Laurent and the Ministère des Ressources naturelles et de la Faune du Québec.

In order to assess the state of the St. Lawrence River ecosystem and its evolution, the partners selected 21 environmental indicators that are related to the ecosystem’s main basic components: the water, riverbed, shores, biological resources and usage. These indicators form part of the partners’ individual permanent data acquisition programs.

Hydrographic Boundaries

The St. Lawrence River alone receives water from seven of the hydrographic regions containing all 430 major watersheds in Québec, covering one third of Québec’s total area.

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