The carbon cycling of eastern Quebec boreal forests in the context of climate change and hydropower production

Hydropower is the main source of electricity to Quebecers and to Canadians, and is an increasingly important export product to the US. Reservoir flooding for hydropower production emits carbon dioxide and methane, two important greenhouse gases. These emissions are low compared to electricity production from non-renewable resources, but they have to be put in the context of a rapidly changing environment due to climate change. Indeed, reservoirs flood areas that were previously largely forests, in addition to aquatic and wetland ecosystems. It is generally assumed that these are net carbon sinks, but this may change in a warmer climate, where droughts, fire and insect epidemics may become more frequent. Hence, to be able to project the net impact of hydropower reservoirs on the climate, we need to understand the impact of intact, surrounding landscapes on the climate, and how this impact evolves. We propose to do this for the La Romaine watershed located on the Côte Nord region of the province of Quebec. The La Romaine complex project was initiated in 2009. At completion in 2021, the complex will comprise four hydroelectric power plants yielding 8.5 TWh of energy per year and four reservoirs covering a total area of 280 km2. We will monitor the carbon fluxes of a subwatershed of La Romaine river, determine the carbon storage hotspots within the subwatershed, and determine the fate of carbon exported in the water from the subwatershed. We will use the results from this exhaustive field study to model the carbon functions of the lower La Romaine watershed, to eventually be able to project the role of this forested landscape in the carbon cycle. Our project will not only be useful to the utility responsible for generation, transmission, and distribution of electricity in the province of Quebec (Hydro-Québec) to assess the true environmental cost of hydropower production, but also to better inform Canada's strategy to partly rely on the carbon sink function of its forests to mitigate future climate change.