About 50,000 large dams across the world will lose 24-28 per cent water storage capacity by 2050 due to sediment trapped in them, a report by the United Nations Institute for Water, Environment and Health showed. These water reservoirs have already lost about 13-19 per cent capacity to sedimentation, the researchers mentioned. The loss will challenge many aspects of national economies, including irrigation, power generation and water supply, said Duminda Perera, who co-authored the study with UNU-INWEH Director Vladimir Smakhtin and Spencer Williams of McGill University in Montreal.