India's
Dams Largest Methane Emitters Among The World's Dams
By Himanshu Thakkar
20 May, 2007
Countercurrents.org
Latest
scientific estimates show that Large dams in India are responsible for
about a fifth of the countries' total global warming impact. The estimates
also reveal that Indian dams are the largest global warming contributors
compared to all other nations. This estimate by Ivan Lima and colleagues
from Brazil 's National Institute for Space Research (INPE) was recently
published in a peer-reviewed journal.
Methane emission from Indian
Large Dams This study estimates that total methane emissions from India's
large dams could be 33.5 million tonnes (MT) per annum, including emissions
from reservoirs (1.1 MT), spillways (13.2 MT) and turbines of hydropower
dams (19.2 MT). Total generation of methane from India's reservoirs
could be 45.8 MT. The difference between the figures of methane generation
and emission is due to the oxidation of methane as it rises from the
bottom of a reservoir to its surface.
The study estimates that
emission of methane from all the reservoirs of the world could be 120
MT per annum. This means that of the total global emissions of methane
due to all human activities, contribution from large dams alone could
be 24%. The study does not include the emission of nitrous oxide and
carbon dioxide from large dams. If all these are included, the global
warming impact of large reservoirs would go up further.
The methane emission from
India 's dams is estimated at 27.86 % of the methane emission from all
the large dams of the world, which is more than the share of any other
country of the world. Brazil comes second with the emission of methane
from Brazil 's reservoirs being 21.8 MT per annum, which is 18.13% of
the global figure.
"It is unfortunate that
Lima 's study has come too late to be included in the recent reports
from the Intergovernmental Panel on Climate Change (IPCC)," says
Patrick McCully, Director of the International Rivers Network. "Climate
policy-makers have largely overlooked the importance of dam-generated
methane. The IPCC urgently needs to address this issue."
These latest round of studies
should further help shatter the myth that power from large hydropower
projects is clean. Indian hydropower projects are already known for
their serious social and environmental impacts on the communities and
environment. The fact that these projects also emit global warming gases
in such significant proportion should further destroy the myth.
Looking at the available
figures for dams in India , total emission of methane from Indian dams
may be somewhat over estimated, but it is still likely to be around
17 MT per annum. Even this more conservative figure means that India's
dams emit about 425 CO2 equivalent MT (considering that global warming
potential over 100 years of a T of methane is equivalent to GWP of 25
T of CO2, as per the latest estimates of IPCC). This, when compared
to India's official emission of 1849 CO2e MT in year 2000 (which does
not include emission from large dams), the contribution of methane emission
from large dams is 18.7% of the total CO2 emission from India.
What needs to be done Indian
government has been blind to this issue so far, even though it has been
known for more than a decade now that reservoirs in tropical climate
are significant source of global warming gases. Neither Central Water
Commission, nor Central Electricity Authority, both premier institutes
of Govt of India, have assessed the global warming impact of India's
large dams and implications there of. The minimum the government can
do is:
· To urgently institute
a credible independent scientific study of global warming impact of
dams in India, in light of findings elsewhere. The study should include
actual measurement of methane and other GHG emission from a sample of
reservoirs.
· While making this
assessment, it should also be assess as to what extent methane emitted
from reservoirs and hydropower projects can be recovered for beneficial
use, in the process also reducing the global warming impact of the reservoirs.
· While assessing
power and water resources development options, the Green house gas emission
potential of dams should be assessed, as part of the cost benefit analysis
and as part of environment impact assessment.
· The IPCC should
initiate an independent study to assess the GHG potential of reservoirs
in different parts of the world, including India. Emission of CO2 from
reservoirs is already part of the mandatory reporting formats of IPCC.
Reporting of methane emissions is suggested, but not mandated. The IPCC
should make reporting of emission of methane from large dams mandatory.
Himanshu Thakkar
( [email protected],
South Asia Network
on Dams, Rivers & People, New Delhi ( www.sandrp.in
)
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