GREENHOUSE GASES FROM BOREAL HYDROELECTRIC RESERVOIRS: 15 YEARS OF DATA?

Tremblay, A. and L. Varfalvy
Hydro-Québec Production, 75 René-Lévesque Blvd West, Montréal, Québec.

Carbon dioxide (CO2) and methane (CH4) are the world's main greenhouse gases and are emitted from both natural aquatic ecosystems (lakes, rivers, estuaries, wetlands) and manmade reservoirs. The role of greenhouse gas emissions from freshwater reservoirs and their potential contribution in increasing atmospheric GHG concentrations is actually well discussed worldwide. To our knowledge, although they are at the heart of the debate concerning pros and cons of different sources of energy production, there are fairly few emission measurements available for fresh water reservoirs on a global basis. Increasing the number of measurements will significantly reduce uncertainties surrounding representative mean gross flux from natural systems as well as from reservoirs. This communication presents data of GHG flux measurements taken on reservoirs of various ages and sizes as well as on adjacent lakes and rivers from Canadian boreal ecosystems. GHG emissions were measured with a floating chamber connected to an automated NDIR instrument giving real-time values. Our results indicate an increase of GHG emissions rapidly after flooding and a return to values of natural systems within 10 years or less. The return to natural ecosystems values is faster for CH4 than for CO2.  Based on 15 years of data, GHG emissions from boreal reservoirs would generally represent 1 to 5% of a thermal power plant of equivalent generation capacity, therefore, boreal reservoirs are very low GHG emitters.

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