Contrasting Eddy Covariance CO2 and CH4 Fluxes from a Hydroelectric Reservoir and Natural Lake in a Boreal Watershed

Boreal landscapes cover a fifth of Canada and act as a globally important carbon sink. However, the majority of Canada’s hydroelectric development is located in boreal landscapes and flooding these landscapes to create reservoirs disturbs their carbon balance. Within boreal regions, aquatic environments act to transport, sequester, and emit carbon but the importance of these processes and the factors controlling them are uncertain. Assessing the net effect of hydroelectric on carbon emissions requires an understanding of CO₂ and CH₄ cycles in reservoirs and the environments they replace. In this presentation, we describe CO₂ and CH₄ flux data from eddy covariance towers at an 80 km² and 44 m deep hydroelectric reservoir (installed spring, 2018) and a 4 km² and 12 m deep natural lake (installed spring, 2022) in the boreal La Romaine watershed in Quebec, Canada (50.85 N, -63.39 W). Using this data and biogeochemical lake models, we will create carbon budgets for both the reservoir and lake and will directly contrast the effect of factors like stratification, ice cover, run-off, and meteorology on their carbon emissions. We expect that the presence of flooded biomass in the reservoir will increase its microbial production of CO₂ and CH₄ and that its distinct morphology and microclimate will affect the seasonality of its carbon flux. This project will contribute to our understanding of the aquatic carbon cycle in boreal regions and will form a base for determining the net carbon effect of hydroelectricity in the boreal region.