Hydro reservoirs are areas of land flooded to retain water for power generation. Reservoirs release green house gases (GHGs) methane and CO2 for up to 10 years after initial flooding. High waters, changes in generation output, erosion during operation also cause emissions. Emissions are created when organic matter (such as trees and plant material, soils) nutrients are broken down and decomposed by bacterial activity.
GHG emissions in reservoirs are the same everywhere in the world but the magnitude varies. Areas of high agricultural activity such as southern Manitoba and Ontario have higher emissions compared to lower productivity areas. GHG emissions from hydro reservoirs are 35-70 times lower per Terrawatt hour than those of thermal generating stations (coal, natural gas).
In a Climate Registry seminar in September, 2009 Manitoba Hydro indicated they are using the Inter-governmental Panel on Climate Change approach that accounts for GHG implications at a national level, rather than for individual projects. This approach would not provide information for new generation projects and reservoirs, or emissions during construction or initial years of operation. This approach also does not include land-use change implications, tends to over-estimate methane emissions, but does not fully account full life cycle accounting for all the potential emissions, to include net implications and so is not accurate.
Emissions accounting for construction and operation of generation stations needs to be included with reservoir emissions accounting.
View Natural Resources Canada CO2 emissions from reservoirs in Quebec
View Climate Registry: GHG Emissions from Hydro Reservoirs event
Download May 2009 The Climate Registry’s presentation (PDF)
Download September 17, 2009 The Climate Registry’s presentation (PDF)
Download September 17, 2009 Manitoba Hydro’s presentation (PDF)