NET GREENHOUSE GAS EMISSIONS AT EASTMAIN 1 RESERVOIR, QUEBEC, CANADA

摘要

Growing concern over the long-term contribution of freshwater reservoirs to increased atmospheric concentration of greenhouse gases (GHGs) led Hydro-Quebec to study net GHG emissions from Eastmain 1 reservoir. These are the emissions resulting from reservoir creation accounting for GHG produced or absorbed by the natural systems over a 100-year period for the watershed as a whole. This large-scale study was carried out in collaboration with the Universite du Quebec a Montreal, McGill University and Environnement Illimite Inc. Gross GHG fluxes were measured using different techniques (eddy covariance, chambers, gas, partial pressure, etc.) for both aquatic and terrestrial ecosystems. More than 120,000 measurements were done over 7 years. The data clearly showed that, prior to flooding, the natural ecosystems overall were a low net source of CO_2 and CH_4. Net GHG emissions from Eastmain 1 increased following impoundment and quickly decreased, with a first-order exponential decay as net emissions would likely stabilized around 10 years after flooding. Diffusive fluxes dominate, with degassing and bubbling emissions representing less than 1% of total emissions. CH_4 emissions are very small and represent less than 1% of total emissions. Overall net GHG emissions from Eastmain 1 reservoir are low in comparison with those from a thermal power plant of the same capacity (about 16%) and would be lower when extrapolated to the entire watershed.