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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-53
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-53
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Feb 2019

Research article | 18 Feb 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

The influence of reservoir traits on carbon dioxide emissions in the Belo Monte hydropower complex, Xingu River, Amazon – Brazil

Kleiton R. Araújo1, Henrique O. Sawakuchi2,3, Dailson J. Bertassoli Júnior4, André O. Sawakuchi1,4, Karina D. Silva1,5, Thiago V. Bernardi1,5, Nicholas D. Ward6,7, and Tatiana S. Pereira1,5 Kleiton R. Araújo et al.
  • 1Programa de Pós Graduação em Biodiversidade e Conservação, Universidade Federal do Pará, Altamira, 68372-040, Brazil
  • 2Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, Brazil
  • 3Department of Ecology and Environmental Science, Umeå University, Umeå, 90187, Sweden
  • 4Instituto de Geociências, Universidade de São Paulo, São Paulo, Brazil
  • 5Faculdade de Ciências Biológicas, Universidade Federal do Pará, Altamira, 68372–040, Brazil
  • 6Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim, Washington, 98382, USA
  • 7School of Oceanography, University of Washington, Seattle, Washington, 98195-5351, USA

Abstract. River damming alters local hydrology, which influences aspects of the carbon cycle such as carbon dioxide (CO2) production and emissions. Run-of-the-river reservoirs (RORs) are designed to have a smaller flooded area than traditional storage reservoirs, maintaining a river flow similar to natural seasonal water level fluctuation. These features may potentially reduce the impacts of the dam on the natural carbon cycle. However, little information on the influence of RORs on the carbon cycle is available, especially for the Amazon or other large tropical rivers. The Belo Monte hydropower complex is a large ROR located in the Xingu River, a clearwater tributary of the Amazon River. It is composed of two reservoirs; the Xingu Reservoir (XR) with ROR characteristics and the Intermediate Reservoir (IR) with storage reservoir traits. Here we evaluate spatiotemporal variation of surface water CO2 partial pressure (pCO2), CO2 fluxes (FCO2), and gas exchange coefficients (k600) during the first two years after the impoundment of the Xingu River. Seasonal changes in the water level had a significant influence on pCO2 with the highest average values observed during high water. The FCO2 was more variable, although correlated with pCO2, throughout the two first years of river impoundment. Spatial heterogeneity was observed for pCO2 during both seasons while FCO2 showed significant spatial heterogeneity only during the high water period. High water FCO2 and pCO2 values were on the same order of magnitude as emissions measured in Amazonian clearwater rivers unaffected by impoundment, but low water values were an order of magnitude higher than previous observations in clearwater rivers with natural flowing waters. Finally, we observed variability in CO2 fluxes related to the type of environment (i.e., river channel, downstream the dams, outside reservoirs and flooded areas), among reservoirs and the land use of flooded areas after impoundment of the Belo Monte hydropower complex. For example, CO2 emissions were 15 % and 90 % higher for the IR compared to XR during high and low water season, respectively, indicating that storage reservoirs may be larger sources of CO2 to the atmosphere compared to RORs. Since many reservoirs are still planned to be constructed in the Amazon and throughout the world, it is critical to evaluate the implications of reservoir traits on CO2 fluxes over their entire life cycle in order to generate energy that has lower emissions per KW.

Kleiton R. Araújo et al.
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Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Kleiton R. Araújo et al.
Kleiton R. Araújo et al.
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Short summary
Little information is available about run-of-the-river carbon dioxide (CO2) emission and how reservoir type influence CO2 production. With this regard we evaluated the CO2 fluxes of Belo Monte hydropower complex and observed variability in CO2 emission related to the type of environment, among reservoirs and the land use of flooded areas after impoundment. Our results emphasize that reservoir type could contribute on CO2 emissions.
Little information is available about run-of-the-river carbon dioxide (CO2) emission and how...
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