About 50,000 large dams around the world could lose more than a quarter of their capacity by 2050 as sediment accumulates, destroying global water and energy security.

According to a UN study, dam capacity is expected to drop from 6 trillion cubic meters to 4.655 trillion cubic meters by 2050, and action must be taken to address this problem and protect vital storage infrastructure.

Silt accumulates in reservoirs as a result of disruption of natural water flows. This can lead to damage to hydroelectric power plants and the interruption of power generation.

Impeding sediment flow along a river can also make upstream areas more susceptible to flooding and destroy downstream habitat.

A U.N. study looked at data from more than 47,000 dams in 150 countries that 16 percent of the original capacity has already been lost. By 2050, the United States will face a loss of 34%, with Brazil estimated to lose 23%, India 26%, and China 20%.

Critics have long warned that the long-term social and environmental costs of giant dams far outweigh their benefits.

Vladimir Smakhtin, director of the UN University Institute for Water, Environment and Health and one of the authors of the study, said that dam construction worldwide has already declined significantly: about 50 dams a year are now built, compared with 1,000 in the middle of last century.