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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.