WINTER GREENHOUSE GASES EMISSIONS FROM BOREAL HYDROELECTRIC RESERVOIRS AND NATURAL LAKES ?

M. Demarty1, J. Bastien1 and A. Tremblay2,

1Environnement Illimité, 1453 Saint-Timothée Montréal, Québec, Canada (maud.demarty@envill.com, Julie.bastien@envill.com)
2Hydro-Québec Production, 75 René-Lévesque Blvd West, Montréal, Québec (tremblay.alain@hydro.qc.ca).

Hydro-Québec is the largest electric power company in Canada with more than 35 000 MW installed for an annual generation of around 189 TWh. Hydro-Québec owns and operates over 57 powerhouses such as Eastmain-1 that was commissioned in 2006. The growing concern regarding the long-term contribution of freshwater reservoirs to atmospheric greenhouse gases (GHG) led Hydro-Québec to study  annual GHG emissions from several reservoirs, including winter season.

This communication presents data of GHG flux (CO2 and CH4)  measurements taken over three years  in Quebec (Canada) during the open-water periods and under-ice in a newly created reservoir (Eastmain-1), a 25 years old reservoir (Robert Bourassa) and in four nearby lakes. While CO2 partial pressure was shown to increase under the ice cover, CH4 partial pressures did not. We were able to estimate the highest CO2 partial pressure that should be reached in the different studied systems just before the ice break-up and beginning of the degassing period, in spring. With these results we estimated annual CO2 and CH4 diffusive fluxes as well as the winter contribution in the overall budget. Our results are clearly demonstrating that in Québec boreal water systems, CH4 diffusive fluxes (in term of CO2 equivalent) was of minor extent in the GHG emissions, CO2 diffusive fluxes representing generally more than 95% of the annual diffusive fluxes.

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