Over a thousand large dams in India will be roughly 50 years old in 2025 and such aging embankments across the world pose a growing threat, according to a UN report which notes that by 2050, most people on Earth will live downstream of tens of thousands of dams built in the 20th century.
The report, titled ‘Ageing water infrastructure: An emerging global risk’ and compiled by United Nations University’s Canadian-based Institute for Water, Environment and Health, says most of the 58,700 large dams worldwide were constructed between 1930 and 1970 with a design life of 50 to 100 years.
It said at 50 years, a large concrete dam “would most probably begin to express signs of ageing.”
Ageing signs include increasing cases of dam failures, progressively increasing costs of dam repair and maintenance, increasing reservoir sedimentation, and loss of a dam’s functionality and effectiveness, “strongly interconnected” manifestations, the report said.
“By 2050, most people on Earth will live downstream of tens of thousands of large dams built in the 20th century, many of them already operating at or beyond their design life,” according to the UN University analysis.
In India, there are over 1,115 large dams that will be roughly 50 years old in 2025, more than 4,250 large dams in the country will be over 50 years old in 2050 and 64 large dams will be more than 150 years old in 2050, it said.
The report said that approximately 3.5 million people are at risk if India’s Mullaperiyar dam in Kerala, built over 100 years ago, “were to fail”.
“The dam, in a seismically active area, shows significant structural flaws and its management is a contentious issue between Kerala and Tamil Nadu States,” it said.
The report added that dams that are well designed, constructed and maintained can “easily” reach 100 years of service but predicts an increase in “decommissioning” – a phenomenon gaining pace in the USA and Europe – as economic and practical limitations prevent ageing dams from being upgraded or if their original use is now obsolete.