Main content area

A method for the assessment of long-term changes in carbon stock by construction of a hydropower reservoir

Bernardo, Julio Werner Yoshioka, Mannich, Michael, Hilgert, Stephan, Fernandes, Cristovão Vicente Scapulatempo, Bleninger, Tobias
Ambio 2017 v.46 no.5 pp. 566-577
carbon, carbon dioxide, carbon sequestration, carbon sinks, case studies, dams (hydrology), greenhouse gas emissions, greenhouse gases, land use, methane, monitoring, rivers, sediments, water power, Brazil
Sustainability of hydropower reservoirs has been questioned since the detection of their greenhouse gas (GHG) emissions which are mainly composed of carbon dioxide and methane. A method to assess the impact on the carbon cycle caused by the transition from a natural river system into a reservoir is presented and discussed. The method evaluates the long term changes in carbon stock instead of the current approach of monitoring and integrating continuous short term fluxes. A case study was conducted in a subtropical reservoir in Brazil, showing that the carbon content within the reservoir exceeds that of the previous landuse. The average carbon sequestration over 43 years since damming was 895 mg C m[Formula: see text] and found to be mainly due to storage of carbon in sediments. These results demonstrate that reservoirs have two opposite effects on the balance of GHGs. By storing organic C in sediments, reservoirs are an important carbon sink. On the other hand, reservoirs increase the flux of methane into the atmosphere. If the sediments of reservoirs could be used for long term C storage, reservoirs might have a positive effect on the balance of GHGs.