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| | | CH4 FLUXES AT EASTMAIN 1 RESERVOIR (QUEBEC, CANADA)
A. Tremblay1 , Caroline L'Heureux and Julie Bastien2
1 : Hydro-Québec Production, Direction Barrages et Environnement, Montréal, Québec (Tremblay.Alain@hydro.qc.ca)
2 : Environnement Illimité Inc., Montréal, Québec (julie.bastien@envill.com)
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 net GHG emissions from Eastmain 1 reservoir. The net emissions are those related to the creation of a reservoir minus those that would have been emitted or absorbed by the natural systems over a 100-year period in the absence of the reservoir. This large study is realized in collaboration with the University of Quebec in Montreal, McGill University and Environnement IIlimité Inc. Carbon dioxide (CO2) and methane (CH4) are the most important gases emitted from hydroelectric reservoirs and they can be emitted by three different pathways: diffusion at the surface of the reservoir, (CO2, CH4), ebullition in the reservoir (mainly for CH4) and degassing in the white waters downstream of the reservoir (mainly CH4). The measurements of CH4 fluxes were conducted by 1) measuring gas partial pressures with gas chromatography during field campaigns (punctual monitoring), 2) with automated systems (continuous monitoring, diffusive and degassing emissions), 3) and by using funnels to collect CH4 bubbles emissions. Follow up of the CO2 and CH4 fluxes at the Eastmain 1 reservoir showed a rapid increase in both CO2 and CH4 emissions the first year after flooding and a rapid return to natural aquatic ecosystem values within two and three years for CH4 and CO2, respectively. All three measurement techniques showed low CH4 emissions indicating that CH4 emissions are not an environmental issue in boreal reservoir. Overall GHG emissions from Eastmain 1 reservoir are very low in comparison to thermal power plants of the same capacity.
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