15 Years of Greenhouse Gases Measurements from Boreal Hydroelectric Reservoirs and Lakes: Are They Different?

[A. Tremblay]
(Hydro-Québec Production, 75 René-Lévesque Blvd West, 10 floor, Montréal, Québec, Canada; ph. 514-289-2211 ext 4416; fax 514-289-5038; email: tremblay.alain@hydro.qc.ca); L. Varfalvy (Hydro-Québec Production, 75 René-Lévesque Blvd West, 2 floor, Montréal, Québec, Canada; ph. 514-289-2211 ext 5358; fax 514-289-4977; email: varfalvy.louis@hydro.qc.ca)

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. 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 over the last 15 years. 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. Many processes related to production and emission of GHG are similar for both lakes and reservoirs, and some are specific to the creation of reservoir.  A synthesis of our actual knowledge will be presented as well as a reflection on the contribution of reservoirs as regulators of climate change.

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