The Mullaperiyar Dam in the southern Indian state of Kerala was built by the British in 1895. It provides crop irrigation and drinking water to thousands of families from a 443 million metre-square reservoir. Since 1959, electricity has also been generated from four 35MW hydropower units built into the dam. 

The dam had an intended lifespan of 50 years. Now, nearly 130 years later, cracks – quite literally – are beginning to show. 

Seismic activity in the area led to cracks first appearing in 1979, and again in 2011. Concerns have arisen over outdated materials and construction methods. Nearly 3.5 million residents would be at risk if the dam burst, but court disputes with the neighbouring state of Tamil Nadu – which operates it – have so far failed to lead to any major plan to modernise the dam. The big fear from the Keralan perspective is that the state could see a repeat of the Morvi Dam failure, whose 1979 collapse after heavy rain killed up to 15,000 people.

The 127-year old Mullaperiyar Dam in Kerala, southern India. (Photo by Getty Images)

The situation at Mullaperiyar is also not unique. “India is one of the biggest dam builders in the world,” says Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People (SANDRP). “We have a stock of very large and very old dams, many of which have growing safety and maintenance issues. Big dams need constant monitoring and maintenance, but unfortunately we are pretty bad at this.” 

After decades of deliberations, India passed its Dam Safety Act – which mandates surveillance and maintenance of large dams – in 2021. But, says Thakkar, the bill “does not inspire confidence” because rather than creating a new regulatory body, the same institutions that have long mismanaged the country’s dams have simply been given larger responsibilities.  

A global problem

The dual problem of ageing dam infrastructure and poor maintenance is not just an Indian problem. Announced hydropower modernisation projects around the world up to 2030 will cost an estimated $127bn, says a 2021 International Energy Agency (IEA) market report; this is only 43% of what is actually needed to maintain the existing fleet. 

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The high cost of maintenance is partly this high because the world’s big dams are ageing: most were built in the 1960s and 1970s, with the average age of installed hydropower capacity now 50 years old in North America, and 43 in Europe. 

It is not only old dams that are at risk of failure. In 2018, the Xe-Pian Xe-Namnoy dam in Laos collapsed, killing at least 40 people and displacing 7,000. The $1.2bn (K18trn) project only began construction in 2013 and was 90% complete at the time of collapse. The Korean company behind the project, SK Engineering & Construction, is accused of cutting corners in order to maximise profits from the construction. 

However, the thousands of ageing dams around the world remain a particular point of anxiety. Dams tend to have a design life of 50–100 years, according to a UN report released last year, but even to make it that long they must be well-designed and well-maintained. As they age, the costs of repair and maintenance will increase, functionality will decrease (as sediment builds up in the reservoir) and the risk of total failure rises. The UN report anticipates that, by 2050, “most people on Earth” will live downstream from tens of thousands of large dams built in the 20th century, a large number of which will be operating far beyond their design life.

Structural risks associated with hydropower are also compounded by climate change. Ecosystems in the Himalayas – where the majority of Indian dams are – are “already in the midst of a crisis”, says Manshi Asher, an environmental researcher based in Himachal Pradesh.

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As glaciers melt and weather becomes more extreme, the risk of flash floods or landslides increases. Not only do these events threaten the structural integrity of dams, but disruptions to river patterns caused by dams can exacerbate the impacts of extreme weather: this year’s floods in Assam, a state in north-eastern India, which submerged 114,000 hectares of crops and killed at least 82, were described as “man-made” by the state's Chief Minister Himanta Biswa Sarma. Soil erosion driven by upstream deforestation is a major cause of the floods, while it was reported that some embankments were only breached after water was released from hydroelectric dams to relieve pressure on their reservoirs. 

An inadequate response

Even as warnings are made that much more needs to be done to effectively maintain and modernise dams, the political priority remains new capacity. Some 600GW of new, large hydropower plants (defined here as having a capacity greater than 50MW) has either been announced, is in permitting or is under construction around the world, shows data from Energy Monitor’s parent company GlobalData. While much of this may not end up being built, it nonetheless shows how governments are keen to expand hydropower capacity even as their existing dams are at risk of failure.

The IEA also called on governments to accelerate hydropower deployment in its Net Zero 2050 road map, saying it should become the third-largest low-carbon source of electricity after solar and wind by mid-century. 

The Indian government, for its part, is now acting to address the risk of ageing dams. As well as signing into law the Dam Safety Act, in 2021, India entered into a $250m (Rs19.9bn) partnership with the World Bank to fund dam modernisation. Approximately 120 dams are set to receive technical and financial support to ensure high strength and safety guidelines are maintained. 

More broadly, the International Commission on Large Dams (ICOLD) is a global body based in France that exists to ensure the world’s 36,000 large dams are both built and operated safely. However, dam failure remains a “growing concern” as dams age and modernisation programmes remain underfunded, says ICOLD’s Emmanuel Grenier.

“We have a situation where most of the world’s dams are ageing, while new dams are appearing in countries that have not built many dams before and whose technical know-how is uncertain,” says Grenier. “It is in everybody’s interest to address this problem, and it is not just human life that is threatened but all manner of business operations that may happen to lie in the vicinity of a dam.”