The impoundment of hydroelectric reservoirs leads to the conversion and circulation, in the aquatic environment, of mercury already present in plants and flooded soil. The result is an increase in fish mercury levels for a period ranging from 10 to 35 years, depending on the fish species and reservoir characteristics. From the early 1980s until about 2010, Hydro-Québec conducted an extensive research program designed, on the one hand, to determine the effects of the increase in mercury on fish, birds and mammals, and on the other hand, to manage the potential risk to the health of fish consumers.

The program’s specific objectives were the following:

  • Study the fate of mercury in natural and modified environments in Northern Québec.
  • Determine the effects of increased fish mercury levels on wildlife.
  • Examine the health risks and benefits of fish consumption.
  • Improve the methods of predicting the impacts of hydroelectric projects.
  • Search for ways to mitigate the increase in fish mercury levels caused by reservoir impoundment.

The results obtained from this program show that mercury levels in modified environments are not harmful to populations of fish, birds and mammals that eat fish. The recent monitoring of fish mercury levels in hydroelectric developments and of the peripheral population’s exposure to mercury have shown that, at the levels of mercury observed in Québec’s reservoirs, the health benefits of eating fish far outweigh the mercury-related risks. Hydro-Québec is now focusing its efforts on developing, in close collaboration with regional public health authorities, consumption guides which will allow recreational anglers and subsistence fishermen to continue to benefit from the great nutritional value of fish while avoiding mercury-related risks.

Specialized documentation

Mercury in reservoirs

Technical reports on the monitoring of mercury in reservoirs

  • GENIVAR. 2012. Aménagement hydroélectrique Sainte-Marguerite-3. Suivi environnemental 2011. Évolution des communautés de poissons et du mercure. (Sainte-Marguerite-3 hydroelectric development. Environmental follow-up 2011. Changes in fish communities and mercury). Report prepared by GENIVAR for Hydro-Québec. 82 p and apps (Report in French) Summary [PDF 47 Kb – in French only]
  • Therrien, J. and Schetagne, R. 2012. Centrales de l'Eastmain-1, de l'Eastmain-1-A et de la Sarcelle et dérivation Rupert. Environmental monitoring during operation phase (2011). Monitoring of fish mercury levels. Joint report by Consortium Waska-GENIVAR and Hydro-Québec Production. 73 p and apps. (Report in French, Executive Summary in PDF format) Summary [PDF 2.4 Mb]
  • Therrien, J. 2011. Suivi environnemental du réservoir Robertson (1990-2010). Évolution des teneurs en mercure dans la chair des poissons. (Environmental monitoring of the Robertson reservoir (1990-2010). Changes in fish communities and mercury). Report prepared by Génivar for Hydro-Québec Distribution. 61 p and apps. (Report in French) Summary [PDF 19 Kb]
  • Schetagne, R., J. Therrien, and R. Lalumière. 2002. Suivi environnemental du complexe La Grande. Évolution des teneurs en mercure dans les poissons. Rapport synthèse 1978-2000. GENIVAR and Hydro-Québec Production. 193 p and apps. Report [PDF 7.8 Mb – in French only]
  • Schetagne, R., J. Therrien, and R. Lalumière. 2013. Environmental Monitoring at the La Grande Complex - Evolution of Fish Mercury Levels. Summary Report 1978-2012. Joint report by GENIVAR and Hydro-Québec Production. 172 p and apps. Summary [PDF 3.0 Mb] Complete Report [PDF 9 Mb]

All these reports are available at Hydro-Québec’s Environment & Communities Documentation Centre.

Monograph: Mercury in northern Québec

  • Lucotte, M., R. Schetagne, N. Thérien, C. Langlois and A. Tremblay. 1999. Mercury in the Biogeochemical Cycle: Natural Environments and Hydroelectric Reservoirs of Northern Québec (Canada). New York, Springer. 334 p Summary [PDF 51 Kb]

This monograph is available for consultation at the following libraries:

  • UQAM’s science library
  • Université de Sherbrooke’s Sciences et Génie (science and engineering) library
  • McGill University’s Schulich Library of Science and Engineering

It is also available at Hydro-Québec’s Environment & Communities Documentation Centre.

Fish consumption guides

To obtain a copy of the guides, call 1 800-363-7443.

Posters and presentations on the mercury issue

Mercury – The Romaine complex

Video: How are fish mercury levels monitored?

Example of the Eastmain-Sarcelle-Rupert complex: In the areas affected by the partial diversion of the Rupert, a team follows the evolution of fish mercury levels. In light of the results, we produce a fish consumption guide in collaboration with the Cree Board of Health and Social Services of James Bay to promote the benefits of healthy fish consumption to Crees.