Do Hydroelectric Reservoirs Emit Greenhouse Gases?

The fluxes of carbon dioxide were determined at the water–air interface using floating chambers connected to an automated nondispersive infrared instrument (NDIR) or a Fourier transform infrared instrument (FTIR). The fluxes were measured in 2002 over 280 sites in Canadian reservoirs, rivers, and natural lakes. Mean measured emissions of CO2 in old Québec reservoirs (> 10 years) were around 1600 ± 1500 mg CO2/m2/day and around 735 ± 1125 mg CO2/m2/day in natural lakes. In a young Québec reservoir (5 years old), values were higher, with mean measured emissions around 4400 ± 4000 mg CO2/m2/day. In Manitoba, old reservoirs had mean values around 3350 ± 2725 mg CO2/m2/day and natural lakes values around 1365 ± 2375 mg CO2/m2/day. In British Columbia, mean values were around 250 ± 800 and 500 ± 650 mg CO2/m2/day, respectively, for old reservoirs and natural lakes. Our data suggest that water quality and the input of carbon from terrestrial systems affect CO2 fluxes from waterbodies. Our results also show that reservoirs older than 10 years are comparable to natural lakes or rivers in terms of the water quality or gross CO2 fluxes and that higher emissions in young reservoir would last 6–8 years.