Emission of CO2 from hydroelectric reservoirs in northern Sweden

• Carbon dioxide in Swedish hydroelectric reservoirs and natural lakes was studied to assess whether the emission of CO2 from inland waters has increased due to construction of reservoirs, and to gauge how the CO2-emission from reservoirs relates to CO2-emission from combustion plants used for electricity production. We found that emission of CO2 from Swedish reservoirs was low and, at corresponding dissolved organic carbon concentration, similar to the CO2-emission from natural oligotrophic lakes. The total annual CO2-emission due to regulation for the seven rivers included in this study (which collectively represents 87% of the total hydroelectricity production in Sweden) was 50,000 tonnes of CO2. This emission represents 1.5 % of the yearly CO2-emission from Swedish electricity combustion plants. Thus, the CO2-emission from Swedish hydropower is much lower per unit of electricity produced than the emission from Swedish combustion plants. Emission of CO2 from Swedish reservoirs was lower than from most reservoirs in other boreal regions of the world. This difference is probably due to that a majority of the Swedish reservoirs are constructed by damming of natural lakes in alpine and upland boreal forest areas, which results in flooding of comparatively small areas with thin layers of soil organic carbon.

Nyckelord

CARBON DIOXIDE; GREENHOUSE GAS; HYDROPOWER; CLIMATE CHANGE

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