THE THREAT OF BECOMING CRUMBLING BLOCKS
The recent Chamoli hydel project disaster has put the focus squarely on India's dams. India has 4,407 large dams, most after China (23,841) and the US (9,263). Over 1,115 large dams will be about 50year-old by 2025. In less than 30 years, by 2050, over 4,250 large dams would pass 50 years of age, with 64 large dams being 150-year-old. Older dams pose greater safety risks, cost higher in terms of maintenance, and have declining functionality due to sedimentation, stated a study by the Canada-based United Nations University Institute for Water, Environment and Health, released in January. Climate change is also likely to accelerate the ageing of dams, it said.
Across the world, many large dams built in the 20th century may start to show signs of ageing, and many may already be operating at or beyond their design life, the study said.
Fifty years is not a defining age for all dams because the design life also depends on factors, such as construction and maintenance, the study said, adding that a well constructed and well maintained dam can go up to a 100 years. However, 50 is roughly the age when a dam may begin to show signs of ageing. In some cases, dam components, such as gates and motors, may need to be replaced after 30 to 50 years.
Therefore, an assessment of the structure should be carried out, and, if needed, the dam should be decommissioned, states the study.
Dodamshavealifeexpectancy?
About 55% of the world's dams are in just four Asian countries, including India. "Dams play a significant role in water supply, energy production, flood control, and irrigation," Duminda Perera and Vladimir Smakhtin of the United Nations University and authors of the study said. "However, we identified that most of the water-storage dams are getting older, leading us to bring this study to the surface. There is no other study to discuss this emerging threat on a global scale."
Structural problems can occur at any stage in a dam's lifespan, but without regular inspections and repairs, ageing increases the risks, said Perera and Smakhtin. "In our report, we selected 50 years as the arbitrary age for a dam to show ageing signs," they said, adding that several kinds of age-related problems can crop up, such as decay or deterioration of the structural materials used in construction and ageing of other components.