Net changes in the regional C balance and the dynamics of GHG emissions following the creation of the Eastmain 1 reservoir in northern Québec, Canada

Alain Tremblay, Julie Bastien, Marie-Claude Bonneville, Paul del Giorgio, Maud Demarty, Michelle Garneau, Jean-Francois Hélie, Luc Pelletier, Yves Prairie, Nigel Roulet, Ian Strachan, Cristian Teodoru

The Eastmain 1 Net Greenhouse Gas (GHG) Emissions Project was launched in 2004 to document the net changes in the regional carbon (C) balance resulting from the construction of the Eastmain 1 reservoir (EM1). All major C sources and sinks of the pre-flood terrestrial and aquatic ecosystems were quantified for 3 years before flooding as well as those from the EM1 reservoir over 4 years after flooding. The total, pre-flood aquatic ecosystems C budget was a net emitter (about 120 t C-CO2 yr-1.km-2 and 0.7 t C-CH4 yr-1.km-2) and the terrestrial ecosystem was a slight CO2 sink  (about -35 t C-CO2 yr-1.km-2) but a source of CH4 (about 3.5 t C-CH4 yr-1.km-2). Overall pre-flood landscape C budget was a natural source of about 7 t C-CO2 yr-1.km-2, and of 2.8 t C-CH4 yr-1.km-2. The post-flood C budget calculated for the first year indicates the EM1 reservoir was a net source of CO2 in the range of 830 t C-CO2 yr-1.km-2 but a much smaller source of CH4 (0.07 t C-CH4 yr-1.km-2). These emissions declined sharply over the following 3 years and tend to stabilize to a constant value of about 174 t C-CO2 yr-1.km-2 within 10 to 15 years.

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