Dams

Dam facts and figures

A Quick Guide to the World of Dams

The World Commission on Dams estimated that there are as many as 48,000 dams over 15m high worldwide. About half of these are in China.
The International Commission on Large Dams (ICOLD) defines a large dam as being over 15 m high. The definition also includes dams between 5-15 m high with a reservoir exceeding 3 million cubic meters.
Dam building peaked in the '70s and declined globally after that. Nevertheless, dam building in China, Turkey, Brazil and India still continues on a large scale.
On average one new dam is build every day and the average construction time is 4 years.
The highest dam in the world is the Rogun Dam in Tajikistan which is 335 m high. The highest dam currently under construction is the 292 m high Xiaowan Dam on the Mekong in China which, when it is completed, will be the highest Arch dam in the world.
Itaipu, shared between Brazil and Paraguay, has the highest installed capacity at the moment, with 12,600 MW. When the Three Gorges Dam is completed it will take over as the dam with the largest capacity, reaching 18,200 MW.
The installation of 1 MW of hydropower capacity costs about $1 million.
About 1500 dams are currently under construction worldwide.
China has a total of 88 dams under construction and at least 36 more dams planned; Turkey has 60 dams under construction and 50 more planned.
China and Turkey, together with Iran and Japan account for 67% of the total number of dams under construction worldwide in 2003.
Hydropower currently provides 19% of the world's total electricity supply, and is used in over 150 countries with 24 of these countries depending on it for 90% of their supply.
30-40% of the 271 million hectares of agricultural land irrigated worldwide rely on dams.
60% of the world's 227 largest rivers are severely fragmented by dams, diversions, and canals - leading to the degradation of ecosystems.
The World Commission on Dams (WCD) estimated that the annual expenditure on large dams during the 1990s was between $32 and $46 billion. Of the $22-31 billion invested in dams each year in developing countries, about four-fifths was financed by the public sector. The WCD calculated that throughout the twentieth century some $2 trillion had been spent on dams.