Boreal rivers are significant sources of carbon dioxide (CO₂) and methane (CH₄) for the atmosphere, but the controls of these emissions are uncertain. We measured 4 months of CO₂ and CH₄ exchanges between a regulated boreal river and the atmosphere with eddy covariance. We found statistical relationships between the gas exchange and several environmental variables, the most important of which were dissolved CO₂ partial pressure in water, wind speed and water temperature.