Dam facts and figures
How many dams are there?
- There are as many as 48,000 dams over 15m high worldwide. About half of these are in China.
- The aggregate storage capacity of all the dams worldwide is about 6,000 km3.
How many new dams are being built?
- Another 1,600 large dams are under construction worldwide in an industry whose annual turnover is estimated at $50 billion or more.
- Together, China, Turkey, Iran, and Japan accounted for 67% of the total number of dams under construction worldwide in 2003.
What do dams do?
- Large dams generate 19% of the world's total electricity supply. One-third of the countries in the world rely on hydropower for more than half their electricity supply.
- Half the world's large dams were built exclusively or primarily for irrigation. Some 30-40% of the 271 million hectares irrigated worldwide rely on dams.
What are dams’ impacts?
- Of the world's 227 largest rivers, 60% are severely fragmented by dams, diversions, and canals, leading to the degradation of ecosystems.
- An estimated 40-80 million people have been displaced from their homes by dam construction.
How much do dams cost?
- The annual expenditure on large dams during the 1990s was between $32 and $46 billion. Throughout the twentieth century some $2 trillion was spent on dams.
1: The World Commission on Dams
2: The International Commission on Large Dams
3: WWF Report. Rivers at Risk: Dams and the Future of Freshwater