Aug 18 2007
Hydropower Disaster for Global Warming by Jaap Krater, Trouw daily
Trouw (daily), Netherlands, 21 January 2007
Large dams have dramatic consequences. Ecosystems are destroyed and numerous people are made homeless, often without adequate resettlement. But it is yet little known that large-scale hydro-electricity is a major contributor to global warming. The reservoirs could, despite their clean image, be even more devastating for our climate than fossil fuel plants.
Another dramatic example is the uprooting of the Chakma in Bangladesh by the Kaptai dam. 40,000 Chakma fled to India, but were not given a legal status. Ensuing violent conflicts around land have led to a brutal end of 10,000 lives.
Mega hydro has an atrocious record. The World Commission on Dams (WCD), consisting of experts, opposition and industry, was installed to produce an independent review of large dams. The WCD estimated in 2000 that 40 to 80 million people have been displaced worldwide. A more recent report by the University of Yale estimates that in India alone, large dams have forced 21 to 40 million people to move. The majority was built for irrigation, but the irrigated agricultural acreage increased by a mere 1%. The World Bank states that more than half of the large hydro projects do not meet their economic targets. Considerable cost overruns are common and have added a considerable burden to the national debt of several developing countries, particularly in South America.
The ecological consequences of large dams are also grim. They include significant and irreversible loss of species, terrestrial and aquatic ecosystems. The massive alteration of major river systems has led to more than a third of the species of sweet water fish to be extinct or endangered.
This can also have economic consequences. Damming the Columbia in the western US resulted in the American government spending 435 million dollar yearly since 1996 on measures to mitigate the impact on fishing in the Colombia basin. Despite the expense, many of the wild salmon species are extinct, or on the brink of extinction.
Despite the social and environmental devastation, large dams can still count on sympathy. After all, they are thought to provide clean energy and thus a weapon in the battle against climate change. But more and more evidence is emerging that suggests something completely different.
When a reservoir fills and land is drowned, the original vegetation starts to rot. The methane that is formed, escapes when the water bursts forth from turbines under pressure. The changing water level due to seasonal variation ensures a continual supply of rotting organic matter. A dam reservoir is, especially in the tropics, like a big engine converting atmospheric carbon into methane, a greenhouse gas 21 times as powerful as carbon dioxide.
The emission of this gas from dam heads has not been modelled until recently. The National Institute for Research in the Amazon has surveyed major dams in Brazil and reports that, thanks to this methane engine, mega hydro emits 3 to 54 times more carbon dioxide-equivalent in greenhouse gases per megawatt than modern gas power stations.
Ironically, climate change itself decreases the effectiveness of hydro-electricity. Many hydro-dependent countries, including Tanzania, Albania, Brazil, Ghana, Norway, Sri Lanka, Tajikistan and Vietnam have suffered serious power shortages due to droughts.
Large dams also affect the climate indirectly. Brazil wants to build three new dams in the Amazon basin to supply electricity to the aluminium industry. Aluminium contributes heavily to climate change, due to emission of large amounts of carbon dioxide and perfluorocarbons: potent, extremely persistent greenhouse agents, released in the electrolytic processing of bauxite. Iceland is building the 190 meter high Karahnukar damn for the American aluminium giant ALCOA: the first in a series, that, when completed, will flood the largest pristine wilderness in Europe.
Iceland has a comfortable amount of yet unspent carbon credits. But Icelandic aluminium smelters will far exceed the 1,600,000 tonnes of emissions permitted under the Kyoto Convention if all of the planned smelter projects materialise.
Like the Sardar Sarovar dam in India, Karahnjukar in Iceland and the industrialisation program are fiercely contested. But the governments of these countries and others still regard mega hydro as a symbol of ingenuity, progress and a matter of national pride. But now that it is becoming evident that hydropower contributes to global warming, it is in all our interest to express to these governments that there are no excuses left for the devastation wrought by large dams.
Published in the newspaper Trouw (Netherlands), 21-1-2007.
Original (in Dutch):
- ‘Role of river-suspended material in the global carbon cycle’ is here in pdf
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- Hydroelectric Power’s Dirty Secret Revealed – New Scientist
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