DAMS .. Dire warning about ageing dams by UN agency; says if they burst, millions would perish


NEWS DAMS DANGER UN MULLAPERIYAR

NEW DELHI: A United Nations report has sounded a grim warning about ageing dams across the world, including India, saying that these are likely to pose serious danger to life in future. A specific mention is made about the Mullaperiyar Dam ( see picture above) in Kerala, a contentious issue between the state and neighbouring Tamil Nadu.

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 about India: “ 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 India will be over 50 years old by 2050 and 64 large dams will be more than 150 years old by 2050.”

The report said approximately 3.5 million people in Kerala are at risk if the Mullaperiyar dam in Kerala, built 125 years ago, “were to fail”. It added, “The dam, in a seismically active area, shows significant structural flaws and its management is a contentious issue between Kerala and Tamil Nadu States.” If the dam breaks, the resultant flood would reach up to the commercial city of Kochi, that has a population of nearly 7 lakh, apart from inundating large swathes of residential areas along a distance of 215kilometres — from the Western Ghats to the Arabian Sea.

The dam, about which there already are safety concerns, was built between 1887 and 1895. It supplies water to Tamil Nadu as well as part of an interstate riparian agreement – between the Maharaja of Travancore, Vaisakham Tirunal Rama Varma with the then Madras Presidency through the good offices of the then reigning British government in India. The dam is situated at the confluence of Mullayar and Periyar rivers.

The report noted that most of the 58,700 large dams worldwide were constructed between 1930 and 1970 with a design life of 50 to 100 years. At about 50 years, any large concrete dam “would (most probably) begin to express signs of ageing. ”In fact, “most people on Earth will live downstream of tens of thousands of dams built in the 20th Century.”

 “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,” the UN report notes.

 The report, in specific, referred to dam decommissioning or ageing case studies from the USA, France, Canada, India, Japan, and Zambia and Zimbabwe. As many as 32,716 large dams (55 per cent of the world’s total) are found in just four Asian countries — China, India, Japan, and South Korea. “A  majority of these will reach the 50-year threshold relatively soon.” The report said the same is true of many large dams in Africa, South America, and Eastern Europe.

ABOUT MULLAPERIYAR: 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.

GLOBAL SCENARIO: The report said that in the US, the average age of 90,580 dams is 56 years. More than 85 per cent of US dams in 2020 were operating at or beyond their life expectancy and 75 per cent of US dam failures occurred after 50 years of age. The estimated cost to refurbish US dams is about $64 billion. Nearly 1,275 dams were removed in 21 US states in the last 30 years; 80 removed in 2017 alone. Worldwide, the huge volume of water stored behind large dams is estimated at 7,000 to 8,300 cubic km – enough to cover about 80 per cent of Canada’s landmass under a metre of water.

The report’s co-author Vladimir Smakhtin, Director of UNU-INWEH, said: “Underlined is the fact that the rising frequency and severity of flooding and other extreme environmental events can overwhelm a dam’s design limits and accelerate a dam’s ageing process. Decisions about decommissioning, therefore, need to be taken in the context of a changing climate.”

Lead author and UNU-INWEH Senior Researcher Duminda Perera said the problem of ageing large dams today confronts a relatively small number of countries – 93 per cent of all the world’s large dams are located in just 25 nations.“Large dam construction surged in the mid-20th Century and peaked in the 1960s – 70s especially in Asia, Europe and North America, while in Africa the peak occurred in the 1980s. The number of newly-constructed large dams after that continuously and progressively declined,” he said.

“Nearly 50 per cent of global river volume is already fragmented or regulated by dams,” the report says.

Public safety, escalating maintenance costs, reservoir sedimentation, and restoration of a natural river ecosystem are among the reasons driving dam decommissioning, the report said, adding that overall, dam decommissioning should be seen as equally important as dam building in the overall planning process on water storage infrastructure developments. — Agencies, IHN-NN

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