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Improve knowledge about pathogenic organisms from agricultural sources found in tributaries of Lac Saint Pierre

Context and project description

What is the risk of contamination of the water in Lake Saint-Pierre by pathogenic organisms that flow into it from the tributaries? And what is the precise relationship with agricultural activities that take place in the watershed? These are the concerns that are the basis for this project, which aims to provide new information on the matter in order to help reduce this type of contamination at the source.

Farm animal excrement in fields and on storage areas (manure piles) can contain various pathogenic organisms that are likely to reach the waterways through runoff or via agricultural drains. This causes a risk for the health of both humans and wildlife. Therefore, the E. coli indicator bacteria will be monitored in the river – upstream and downstream from the lake – as well as in the tributaries. Since the organisms' resistance to antibiotics and the chance of transferring resistant genes increase the risks to health, we will also attempt to measure this resistance. We will also conduct exploratory monitoring of the parasites Giardia and Cryptosporidium and the bacteria Campylobacter in the raw water at four water intakes located at the mouths of the Lake Saint-Pierre tributaries and in the river upstream and downstream from the lake. Lastly, we will study the relationships between the indicator organisms or pathogens detected in the water samples and the agricultural contamination sources. Other studies, by partners and collaborators, may eventually be added to the project.


In this SLAP project, monitoring of raw water around four drinking-water intakes in Lake Saint-Pierre was carried out to detect the presence of the protozoans (microorganisms) Giardia and Cryptosporidium and the bacterium E. coli. The water intake operators were informed of the results of the raw water analyses as they became available. The raw water from two of the water intakes contained some of the highest Giardia and Cryptosporidium concentrations among all the samples analyzed from water intakes. With regard to the bacterium E. coli, three out of four water intakes contained levels that greatly exceeded the acceptable threshold (150 CFU/100 mL), indicating that the raw water is often degraded and requires enhanced treatment. The results are presented on pages 30 to 33 of the report titled Bilan de la qualité de l’eau potable au Québec 2010–2014External link available only in french on the website of the Quebec Department of Sustainable Development, Wildlife and the Fight Against Climate Change.

Participating departments

Government of Canada

  • Health Canada

Government of Quebec

  • Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques