Title: Carbon dioxide (CO₂) concentrations and emission in the newly constructed Belo Monte hydropower complex in the Xingu River, Amazonia

Abstract

The Belo Monte hydropower complex located in the Xingu River is the largest run-of-the-river (ROR) hydroelectric system in the world and has one of the highest energy production capacities among dams. Its construction received significant media attention due to its potential social and environmental impacts. It is composed of two ROR reservoirs: the Xingu Reservoir (XR) in the Xingu's main branch and the Intermediate Reservoir (IR), an artificial reservoir fed by waters diverted from the Xingu River with longer water residence time compared to XR. We aimed to evaluate spatiotemporal variations in CO₂ partial pressure (pCO₂) and CO₂ fluxes (FCO₂) during the first 2 years after the Xingu River impoundment under the hypothesis that each reservoir has contrasting FCO₂ and pCO₂ as vegetation clearing reduces flooded area emissions. Time of the year had a significant influence on pCO₂ with the highest average values observed during the high-water season. Spatial heterogeneity throughout the entire study area was observed for pCO2 during both low- and high-water seasons. FCO₂, on the other hand, only showed significant spatial heterogeneity during the high-water period. FCO₂ (0.90±0.47 and 1.08±0.62 µmol m² d^–1 for XR and IR, respectively) and pCO₂ (1647±698 and 1676±323 µatm for XR andmore » IR, respectively) measured during the high-water season were on the same order of magnitude as previous observations in other Amazonian clearwater rivers unaffected by impoundment during the same season. In contrast, during the low-water season FCO₂ (0.69±0.28 and 7.32±4.07 µmol m² d^–1 for XR and IR, respectively) and pCO₂ (839±646 and 1797±354 µatm for XR and IR, respectively) in IR were an order of magnitude higher than literature FCO₂ observations in clearwater rivers with naturally flowing waters. When CO₂ emissions are compared between reservoirs, IR emissions were 90 % higher than values from the XR during low-water season, reinforcing the clear influence of reservoir characteristics on CO₂ emissions. Based on our observations in the Belo Monte hydropower complex, CO₂ emissions from ROR reservoirs to the atmosphere are in the range of natural Amazonian rivers. However, the associated reservoir (IR) may exceed natural river emission rates due to the preimpounding vegetation influence. 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 FCO₂ over their entire life cycle in order to improve estimates of CO₂ emissions per kilowatt for hydropower projects planned for tropical rivers.« less

Authors:

de Araújo, Kleiton R. ^[1]; Sawakuchi, Henrique O.  ^[2];

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Bertassoli Jr., Dailson J. ^[3]; Sawakuchi, André O. ^[4]; da Silva, Karina D. ^[5]; Vieira, Thiago B. ^[5]; Ward, Nicholas D. ^[6]; Pereira, Tatiana S. ^[5]

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+ Show Author Affiliations

1. Univ. Federal do Para, Altamira (Brazil)
2. Univ. de Sao Paulo, Piracicaba (Brazil); Umea Univ., Umea (Sweden); Linkoping Univ., Linkoping (Sweden)
3. Univ. de Sao Paulo, Sao Paulo (Brazil)
4. Univ. Federal do Para, Altamira (Brazil); Univ. de Sao Paulo, Sao Paulo (Brazil)
5. Univ. Federal do Para, Altamira (Brazil); Univ. Federal do Para, Altamira (Brazil)
6. Pacific Northwest National Lab. (PNNL), Sequim, WA (United States); Univ. of Washington, Seattle, WA (United States)

Publication Date:

Wed Sep 18 00:00:00 EDT 2019

Research Org.:

Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1576777

Report Number(s):

PNNL-SA-140925
Journal ID: ISSN 1726-4189

Grant/Contract Number:  

AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Biogeosciences (Online)

Additional Journal Information:

Journal Name: Biogeosciences (Online); Journal Volume: 16; Journal Issue: 18; Journal ID: ISSN 1726-4189

Publisher:

European Geosciences Union

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Amazon; aquatic; Bel Monte; biogeochemistry; carbon cycling; carbon dioxide; decomposition; disturbance; ecosystem; emission; gradients; hydroelectric dam; outgassing; reservoirs; terrestial aquatic interface; tidal river; wetland; wetland inundation