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| Titel |
The net GHG (CO2, CH4 and N2O) footprint of a newly impounded subtropical hydroelectric reservoir: Nam Theun 2 |
| VerfasserIn |
Chandrashekhar Deshmukh, Frederic Guerin, Claire Delon, Sylvie Pighini, Axay Vongkhamsao, Stéphane Descloux, Vincent Chanudet, Raphael Tardif, Arnaud Godon, Pierre Guédant, Corinne Galy-Lacaux, Cyril Zouiten, Priscia Oliva, Stephane Audry, Dominique Serça |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081844
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| Zusammenfassung |
| There is a rising concern over the contribution of hydroelectric reservoirs to global
anthropogenic greenhouse gases (GHGs) emissions. We present here the first comprehensive
assessment of GHGs footprint associated with the creation of the Nam Theun 2 (NT2)
hydroelectric reservoir in subtropical region of the Lao People’s Democratic Republic. This
assessment is the results of a monthly monitoring that have been conducted over 4 year
(2008-to date). The carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)
sources and sinks were quantified before and after impoundment, which began in May
2008.
Before impoundment, the landscape to be flooded was a sink of carbon dioxide (-73 ±
225 Gg CO2eq yr-1),roughly neutral in terms of methane (7 ± 11 Gg CO2eq yr-1), and a
source of nitrous oxide (345 ± 158 Gg CO2eq yr-1). After impoundment, total CO2 and
CH4 emissions increased and N2O emissions decreased. For the year 2010, CO2 (791 ± 54
Gg CO2eq yr-1) and CH4 (644 ± 124 Gg CO2eq yr-1) contributed equally to the total gross
GHG emissions from NT2 (54 and 43% for CO2 and CH4, respectively) whereas N2O
contributed only 3% (47 ± 29 Gg CO2eq yr-1). The GHG emissions remained
constant in 2011. Our results indicate that most of the GHG (around 90%) were
emitted from reservoir water surface and the drawdown area, and only 10% were
emitted by degassing at the turbines and from diffusive emissions downstream of
the turbines and the dam, a percentage lower than reported for other hydroelectric
reservoirs.
With a total emissions of 1482 ± 207 and 1298 ± 200 Gg CO2eq yr-1 for year 2010 and
2011, gross NT2 emissions are about an order of magnitude higher than pre-impoundment
emissions (276 ± 393 Gg CO2eq yr-1). With a net GHG emissions of 1203 ± 601 (2010)
and 1022 ± 594 (2011) Gg CO2eq yr-1, and an annual power generation of about 6 TWh,
GHG emission factor equal to 0.20 (2010) and 0.17 (2011) Mg CO2eq MWh-1 for NT2
which is up to five times lower than the emission factor of a thermal power plant (ranging
from 0.44 to 1.05 Mg CO2eq MWh-1). Since emissions are supposed to decrease
with the age of the reservoir, 2010 emission factor probably corresponds to the
maximum value that would be reached for this reservoir. Work is in progress to predict
the trends of GHG emissions over the projected life span (e.g. 100 years) of the
reservoir. Integration of net GHG emissions at this time scale will allow a better
comparison of emission factor of hydropower generation with other alternate energy
sources.
Keywords: Net GHG emissions, subtropical hydroelectric reservoir, Nam Theun 2 |
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