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Using Sediments to tell the Story of Lake Manicouagan

April 27, 2022 | Audrey-Maude Vézina

Update : May 5, 2023

Field work in the Côte-Nord region is tracing the effects of the Manic-5 dam since its construction on Lake Manicouagan.

Armed with long PVC tubes, the team collects a sedimentary core in the Manicouagan reservoir.

A resounding success! This is how Professor Pierre Francus of the Institut national de la recherche scientifique (INRS) describes a recent expedition to Manicouagan, in the Côte-Nord region. His team, led by Léo Chassiot, an associate professor at INRS, conducted a core sampling campaign over two weeks. Armed with long PVC tubes, the team collected about 20 sedimentary cores in the Manicouagan reservoir, which is some 70 kilometres wide and 400 metres deep. Quite a challenge!

These sedimentary archives will be used to explore the environmental history of the region, with a focus on the effects of the Manic-5 dam, which raised the water level by 140 metres.

“We will be able to determine how the infrastructure has affected the health of the lake by looking at the changing properties of the sediments that have been deposited over time.”

Léo Chassiot, who is also a research professional at Université Laval.

Among others, the team will analyze changes in sedimentary deposits before and after the dam construction, including the quality and quantity of organic matter, oxygen rate tracers, and the presence of metals.

Researchers were able to sample at almost all of the chosen sites. Professor Francus remarked: “In my career, I have never experienced a field expedition with such a high success rate. Usually, we’re thrilled if we can sample half of the sites. Here, it’s exceptional!”

Community discussions

The project was a success in part thanks to the Innu community of Pessamit, which saw its ancestral land flooded when the reservoir was created. The Conseil des Innus de Pessamit (Innu council of Pessamit) manages the Uapishka Station in collaboration with the Manicouagan-Uapishka World Biosphere Reserve (UNESCO). This infrastructure is essential to allow field research to run smoothly and the researchers are grateful to have received such excellent guidance.

Léo Chassiot was accompanied on the expedition by research officer Arnaud De Coninck, from Professor Francus’ team, and Samuel Couture, a master’s student at Université Laval. The trio of researchers was supported by Anthony Bacon, a member of the Pessamit community who works at the Uapishka Station.

“The contribution of Anthony Bacon to this mission was also a major factor in its success. We had a great time,” says Léo Chassiot. “We had some interesting discussions, he was curious about why and how we were collecting sediments, both on a technical and a scientific level. And thanks to him, we got out of several bad situations. He also taught us a lot about the Pessamiulnuat, Innu culture, and the ongoing issues around developing the land.”

“This region remains underexplored compared to others in Quebec. It has a unique ecosystem with the Groulx Mountains, also called Uapishka Mountains—meaning ‘always snowy rocky peaks’—which overlook the reservoir. There are challenges both in basic science and in the development of collaborative research with First Nations,” he adds.

The project is funded by the Institut nordique du Québec (INQ) and Sentinel North. It will take advantage of INRS’s state-of-the-art research infrastructure in the CT Scanning for Civil Engineering and Natural Resources Laboratory and the Geochemistry, Imaging, and Radiography of Sediments Laboratory.

Professor Francus is currently recruiting a master’s student to analyze the sediment cores collected from the Manic-5 reservoir.

Analyse de l’effet de l’ennoiement du lac Manicouagan par le barrage Daniel-Johnson sur la sédimentation lacustre