In:
Biogeosciences, Copernicus GmbH, Vol. 16, No. 18 ( 2019-09-18), p. 3527-3542
Abstract:
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 and 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.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-16-3527-2019
DOI:
10.5194/bg-16-3527-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2158181-2
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