There is still much uncertainty concerning the magnitude of greenhouse gas (GHG) emissions attributable to reservoirs. This uncertainty results from a lack of clear accounting methodologies to determine pre- and post-flood GHG balances (i.e. net carbon footprint), incomplete accounting of all major emission pathways (i.e., diffusion, ebullition, degassing), and insufficient understanding of the spatio-temporal variability of these emissions. Here we present the net carbon footprint for the newly created La Romaine 2 reservoir (RO2), located in Eastern Canada. We sampled RO2 intensively over the first 4 years after flooding. The pre-flood GHG balance was estimated via landscape modeling. For the post-flood GHG balance, we modeled CO₂ and CH₄ surface water concentrations based on field data to create a grid across the whole reservoir to incorporate  spatio-temporal variability and overlayed this grid with spatially explicit gas transfer velocities to calculate diffusive fluxes. Measured ebullition fluxes were propagated over the grid based on depth and temperature, and outflow degassing was estimated based on continuous CO₂ and CH₄ measurements and water discharge at the turbine. Here we describe the evolution of the C footprint and of its components over the first four years of flooding, and conclude that the net C emissions relative to generating capacity are low compared to other reservoirs that have been studied, due to the particular reservoir configuration. The framework applied here can be transposed to other reservoirs for more robust accounting of their C footprints.

Primary Presenter: Paul del Giorgio, Univ. du Quebec a Montreal (del_giorgio.paul@uqam.ca)

Authors:

Pascal Bodmer, Université du Québec à Montréal  (bodmerpascal@gmail.com)

Joan-Pere Casas-Ruiz, University of Girona  (jpcasasruiz@gmail.com)

François Bilodeau, Hydro-Québec  (bilodeau.francois@hydroquebec.com)

Felipe Rust, Université du Québec à Montréal  (rustfelipe@gmail.com)

Alain Tremblay, Hydro-Québec  (tremblay.alain@hydroquebec.com)

Päul del Giorgio, Univesrité du Québec à Montréal  (del_giorgio.paul@uqam.ca)