Aller directement au contenu.

Nonpoint source pollution

Point sources of contamination in the waters of the St. Lawrence, such as municipal and industrial effluents, are fairly well characterized and localized. On the other hand, nutrients and various contaminants from the agricultural areas cause nonpoint source pollution, which is at the origin of eutrophication and contamination problems in the waters of the St. Lawrence. Research of new solutions to reduce the sources and impacts of nonpoint pollution is necessary.

Projects 2016-2021

Map the bodies of water present in Lake Saint-Pierre in support of water quality monitoring

Lake Saint-Pierre, a bulge in the river upstream from Trois-Rivières, is very rich in biodiversity. It is on the list of internationally significant wetlands (Ramsar site) and is part of UNESCO’s coastal biosphere reserves. However, it receives a large number of agricultural contaminants, including pesticides.

The researchers in this project will use hydrodynamic modelling to provide a daily mapping of the different bodies of water that form Lake Saint-Pierre according to average hydrological conditions of the 24 previous hours. The provided mapping is representative of the contributions of each of Lake Saint-Pierre’s outlets in terms of flow and water quality. The maps provide support water quality monitoring in three ways:

  • By locating areas most susceptible to being affected by agricultural contaminants;
  • By determining each outlet’s zone of influence; and
  • By allowing the sampling plan to be adjusted by revising the locations of the data sampling sites.

Assess the effectiveness of wet-retention ponds to improve the water quality of agricultural watersheds

The waterways that empty into Lake Saint-Pierre often contain pesticides, nutrients (nitrogen and phosphorus) and suspended solids that can hinder aquatic life. A large proportion of these pollutants come from farming located within the lake’s watershed. We believe, however, that the use of the water retention ponds can attenuate the impacts of non-point source pollution in an agricultural environment. When the water slows while passing through the water retention pond, the pesticides and the nutrients are retained by the sedimentation and can degrade during contact with plants and organisms. As such, the water retention pond can reduce the contaminants present in surface water and in agricultural drainage.
The researchers in this new project will assess the effectiveness of such water retention ponds. If this approach is effective, it may become an economical and durable solution for the agricultural sector.

The researchers in this new project assess the effectiveness of such water retention ponds. A recent study of the pond shows great results in terms of nutriments retention, MES and pesticides ( glyphosate and its degradation product AMPA and thiamethoxam). However, toxics found in pond water have consequences on algae growth and on the American Toad development. In addition, the pond is a favourable environment for greenhouse gases (GHG) production.

Improve knowledge about pathogenic organisms of the Lake Saint-Pierre watershed

Runoff brings organisms that are potentially dangerous for humans and wildlife into Lake Saint-Pierre. Indeed, in the first phase of the SLAP, our researchers observed a significant quantity of E. Coli in the tributaries of the lake, which indicates fecal contamination and the presence of potentially pathogenic organisms. They also discovered that these bacteria were resistant to several antibiotics. Furthermore, the Giardia and Cryptosporidium parasites were measured in raw water and four water intakes.
We do not as of yet know the actual risk of this type of pollution, or the source of the bacteriological contamination observed in the tributary waterways of Lake Saint-Pierre. In a series of publications, our researchers present the results of pathogenic organism measurements in these waterways at different locations. They also identify the sources of the contaminants in order to help guide remediation actions.

Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques. 2016. Bilan de la qualité de l’eau potable au Québec 2010-2014. 80 pages : link ( in French only). 

Villemur, R., M. Imbeau, M.N. Vuong, L. Masson et P.  Payment (2015). An environmental survey of surface waters using mitochondrial DNA from human, bovine and porcine origin as fecal source tracking markers. Water Research, 69, 143-153. link 

Evolution of Lake Saint-Pierre’s aquatic-grass beds

Lake Saint-Pierre’s aquatic-grass beds provide an essential habitat for fish, amphibians and aquatic birds. Aquatic plants act as physical support for algae and crustaceans that feed vertebrates and provide them with shelter against predators. However, we do not clearly understand the plants that form these beds and the way in which the aquatic-grass beds evolve in time as a function of the quantity (depth and current) and the quality (transparency and nutrients) of the water.
Our researchers produce a portrait of Lake Saint-Pierre’s aquatic-grass beds and the aquatic plant and algae biomass in order to characterize the available habitat for fish and invertebrates. By following the aquatic-grass beds over several years and working on the recent history of the abundance of plants, the researchers assess the factors that influence the condition of the beds and determine their sensitivity to climate change. At the end of the project, our researchers are able to determine the restoration measures that can be implemented in the next phases of the SLAP.

Prepare and hold an exchange workshop on Lake Saint-Pierre

Several factors contributed to the degradation of Lake Saint-Pierre’s coastal habitats and to major changes in the ecosystems that have been observed over the past years. Take, for example, the agricultural activities in flood-prone areas, the significant year-to-year variability in water levels related to climate change and the presence of several pesticides in the lake waters.
This project aims to bring together researchers from different disciplines in an exchange workshop in order to share the research results on Lake Saint-Pierre. These exchanges will provide an update on the evolution of susceptible stress factors that explain changes in this ecosystem’s support capacity.

Exchange workshop on Lake Saint-Pierre 2019 - Summary

Assess the effects of pesticides on aquatic organisms

Intensive agricultural activities in regions like Lake Saint-Pierre are a possible cause of the degradation of the aquatic environment. Presently, the effects of pesticides on Lake Saint-Pierre’s aquatic wildlife in sectors bordering the river or brought in by tributaries remains poorly understood. However, we know that these tributaries draining from agricultural lands dominated by corn and soybean cultivation and the herbicides most used for this type of cultivation, including atrazine, metolachlor and glyphosate, are detected in neighbouring rivers. More recently, the presence of neonicotinoid-type insecticides has also been reported. The combined presence of herbicides and insecticides can therefore affect the aquatic wildlife of this sector.
The researchers in this project assess the effects of exposure of aquatic organisms to the pesticides used on agricultural lands of the St. Lawrence River watershed, particularly the aquatic organisms present in Lake Saint-Pierre. The study determine the concentration of the various pesticides in the water, measure their effects on aquatic organisms, such as fish, frogs and invertebrates exposed in their natural environment or in a laboratory, and monitor populations of fish and aquatic invertebrates.

Projects 2011-2016

Richelieu's "Corridor Vert et Bleu"

The Richelieu River is a jewel of biodiversity. It is home to a number of species in precarious situations, among them the copper redhorse. However, urban development and agricultural practices pose major challenges in terms of improving the river’s water quality and habitats. Moreover, the sediment and pollutants observed in the Richelieu flow into Lake Saint-Pierre. One-time restoration measures along the shorelines in this watershed are not sufficient for maintaining adequate water quality, and the participants and collaborators in the St. Lawrence Action Plan seek to implement a comprehensive conservation and restoration project. This initiative will make it possible to conserve a riparian strip to reduce water pollution and create an ecological corridor, install sedimentation systems in ditches and preserve, restore and connect natural spaces throughout the watershed area.

Read the explanatory brochure for the project.

Read the backgrounder for this project.

Develop agricultural water courses on the coastline in the lake Saint-Pierre flood plain

A significant portion of the Lake Saint-Pierre shoreline is used for agricultural purposes, with large blocks of land being gradually converted for large-scale farming, which reduces the substrate of plant material available in the spring for fish habitats. Several participants and collaborators have partnered to develop an approach for restoring these fish habitats. Seven watercourses have been restored since 2003, and this initiative will remain ongoing at a rate of one watercourse per year through 2016 to continue raising the profile of the Lake Saint-Pierre region in terms of sustainable agriculture.

Read the backgrounder for this project.

Continue the activities of the Agriculture Coordination Committee

The objective of this project is to foster increased collaboration among the leading stakeholders in the agriculture sector to establish a common vision of the environmental issues relating to the water quality of the St. Lawrence and its tributaries and to define solutions for protecting these aquatic ecosystems from an integrated management perspective.

Document riverine inputs of organic carbon and nutrients into the marine estuary in relation to hypoxia and acidification

An increase in riverine inputs of organic carbon and nutrients associated with human activities could lead to a eutrophication phenomenon in estuaries and coastal areas. This eutrophication can cause the proliferation of toxic or otherwise harmful algae and the development of hypoxic or acidified zones potentially threatening the health of the St. Lawrence. Documenting the sources and historical evolution of inputs of nutrients and organic matter and the effects of an increase in these inputs, along with the development of numerical prediction tools, will help add to knowledge in this area and support better prediction of these phenomena frequently linked to nonpoint agricultural pollution sources. 

Read the backgrounder for this project.

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

Livestock manure, cultivated fields and storage areas (manure piles and exercise yards) can contain pathogenic organisms that, on reaching waterways through runoff or agricultural drains, pose a risk to animals and people. In light of the fact that the fecal coliform concentrations measured in tributaries of Lake Saint-Pierre point to the potential presence of pathogenic bacteria, the partners and collaborators seek to gain a better understanding of the risk of water contamination caused by these pathogenic organisms by examining their links to agriculture and providing new information that may assist in decreasing this type of contamination at the source.

Read the backgrounder for this project.

Use the effects of harmful and toxic algae as indicators for monitoring the quality and eutrophication of the water

The proliferation of harmful and toxic algae in the St. Lawrence ecosystem constitutes a growing problem, the effects of which are not yet fully understood. The development of expertise will help provide a clearer understanding of the influence of these algae on the ecosystems in which they proliferate, whether in terms of identifying toxic algae, documenting the factors associated with their bloom and the production and spread of toxins or developing biomarkers and bioindicators. Adding to knowledge about these phenomena will enable the development of prediction tools for sectors at risk and the ecosystem components known to be sensitive to harmful and toxic algae.

Read the backgrounder for this project.