Modelling OM sources and Processing in the La Romaine Hydroelectric Complex to Improve Attribution of Reservoir Carbon Dioxide Emissions

Although hydroelectricity has been considered a carbon-neutral energy source in the past, it is now recognized that the creation of hydroelectric reservoirs leads to GHG emissions due to land-use change caused by the impoundment of natural ecosystems. Quantifying robust carbon footprint for reservoirs requires separating emissions attributable to the reservoir, i.e., the mineralization of flooded organic carbon pools, from "natural" emissions, i.e., the degradation of DOC derived from the watershed. Here we present preliminary results of a study that reconstructs the watershed loading of DOC and its subsequent biotic and abiotic processing within three young and consecutive boreal reservoirs. This project is part of the long-term research program of the CarBBAS (Carbon Biogeochemistry in Boreal Aquatic Ecosystems) group to quantify the carbon footprint of the La Romaine hydroelectric complex in Quebec, Canada. For each reservoir we have developed a complete water balance and a full DOC mass balance using DOC concentration data from La Romaine River and dozens of tributaries within the watershed. A mechanistic model will then be used to model the DOC degradation within the reservoirs, based on the measured biological and photochemical reactivity of the incoming watershed DOC and the hydrologic residence time. The objective is to eventually subtract the resulting CO2 fluxes from the CO2 diffusive emissions that have been measured at the reservoir air/water interface, to better constrain GHG emissions that are attributable to the reservoirs.

Primary Presenter: Camille St-Arneault, Université du Québec à Montréal (st-arneault_sergerie.camille@courrier.uqam.ca)

Authors:

Camille St-Arneault, Groupe de recherche interuniversitaire en limnologie (GRIL), Université du Québec à Montréal  (st-arneault_sergerie.camille@courrier.uqam.ca)

Paul del Giorgio, Groupe de recherche interuniversitaire en limnologie (GRIL), Université du Québec à Montréal  (del_giorgio.paul@uqam.ca)

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