A new Oxford study looking at 245 dams in 65 countries finds that large dam projects run an average of 96 percent over budget and take an average of 2.3 years longer to complete than originally planned. The report mostly targets so-called megadams, recommending that emerging-market countries focus on smaller dams, which are more likely to be economically viable. An extreme case—Brazil’s Itaipu Dam—ran 240 percent over budget.
The report also found that large dams are not actually carbon-neutral given the large amount of concrete involved and methane produced by flooded vegetation in reservoirs.
No country has embraced dam-building with quite the enthusiasm of China, which has constructed more than 20,000 large dams in the last 60 years, including the controversial $59 billion Three Gorges Dam, which displaced more than a million people. China’s pace of construction slowed under former Primier Wen Jiabao, who intervened to block the construction of several projects, but looks set to accelerate again as the country finds itself up against steep power generation and emissions reduction targets.
The world’s largest planned hydroelectric project, Brazil’s Belo Monte dam, was halted by a judge last year after a legal challenge by indigenous groups in the area.