Big is beautiful 2
Do massive dams ever make sense?
-- a _kt75 | reprint
A new report from researchers at Oxford University argues that large dams are a risky investment - soaring past projected budgets, drowning emerging economies in debt and failing to deliver promised benefits. Do they ever really make sense?A peek over the edge of the Hoover Dam's 60-storey wall is enough to send shivers down anyone's spine. Constructed from enough concrete to pave a motorway from New York to San Francisco - this colossal barrier is touted as a symbol of man's mastery over nature and a marvel of 20th Century engineering.
The dam was credited with helping jump-start America's economy after the Great Depression, reining in the flood-prone Colorado River and generating cheap hydroelectric power for arid south-western states. Even more miraculously, the Hoover Dam was completed two years ahead of schedule and roughly $15m (£9m) under budget.
But for megadam critics, the Hoover Dam is an anomaly. The Oxford researchers reviewed 245 large dams - those with a wall height over 15m (49ft) - built between 1934 and 2007. They found that the dams ran 96% over their approved budgets on average - Brazil's Itaipu dam suffered a 240% overrun - and took an average of 8.2 years to build. In the vast majority of cases, they say, megadams are not economically viable. But after a two-decade lull, large dams are once again being trumpeted as a ticket to prosperity. Countries from China to Brazil, via Pakistan and Ethiopia, are rushing to erect them. With world electricity consumption expected to grow by more than 56% between 2010 and 2040, according to the 2013 International Energy Outlook report, hydropower is a tempting option. More than 90% of the world's renewable electricity comes from dams, according to the International Commission on Large Dams.
Andy Hughes of the British Dam Society points to Laos and Vietnam as shining examples of dam-building countries that have harnessed hydropower. "They're building dams, they're generating hydropower, and then they export that power to other countries, so it's a big cash crop for them," he says.But Bent Flyvbjerg, principal investigator for the Oxford University dam study, says dams "are not carbon neutral, and they're not greenhouse neutral". The vast quantities of concrete required to construct leave an enormous carbon footprint, he says. Furthermore flooded vegetation under the reservoirs produces methane, a greenhouse gas roughly 20 times more potent than carbon dioxide, he says. His argument is not with all dams though, but with megadams. "We don't accept that it's a discussion of hydropower from large dams versus fossil fuels. We would like the discussion to be about hydropower from large dams versus hydropower from smaller hydropower projects," he says. Read on...
Read also: [1], [2], [3], [4], [5], [6], [7], [8], [9]
