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The myth of brown waters: swimming potential in the Châteauguay River

Brown water is often referred to as poor quality water. However, this is not always the case!

This is what Fondation Rivières and Society for the conservation and development of watersheds in the Châteauguay area (SCABRIC) wanted to demonstrate during the summer of 2021. They brought together most of the municipalities bordering the Châteauguay River to carry out a unpublished study on the quality of river water.

Positive results

The main objective of this project was to draw up an accurate portrait of the bacteriological quality of the water of the Châteauguay River and to evaluate the potential to open swimming sites in participating cities: Châteauguay, Mercier, Sainte-Martine, Howick, Ormstown, Dewittville and Huntingdon.

In dry weather, the bacteriological quality of the water is very good and even excellent in certain places. Only the sector downstream of the river seems to present a risk of contamination in dry weather, therefore in summer. Regarding the bacteriological quality of the water, safe swimming is therefore possible in the river!

Intensive field work… and collaboration!

Fondation Rivières carried out hybrid monitoring of the water quality of the river, using both traditional analyzes ofE.coli in the laboratory and a new rapid analysis technology, the ColiMinder. The device can detect in 15 minutes the presence ofE.coli in water by enzymatic analysis and to automate monitoring by allowing sampling at a high frequency and access to the results via an online platform. This hybrid monitoring methodology, coupled with intensive field work, made it possible to draw up a portrait of the bacteriological quality of water over 55 km of river.

This study illustrates an exceptional level of consultation between municipalities and the crucial role played by SCABRIC in bringing together all stakeholders. Taking an interest in the swimming potential makes it possible to mobilize stakeholders and motivate municipalities to make the river accessible to citizens and therefore, to depollute a precious local resource.

When will there be a swimming site in Châteauguay?

In 2020, Fondation Rivières demonstrated that the water of the L'Assomption river was of good enough quality for swimming. The town of L'Assomption now operates a popular and safe public beach there.

As for Châteauguay, additional studies will make it possible to establish safety protocols specific to each site and eliminate sources of contamination in dry weather. So, just because the water in a river is brown does not mean its quality is necessarily bad!

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Photo credit: Christophe Gravel / CC


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