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."
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".
From the report available at https://inweh.unu.edu/wp-content/uploads/2021/01/Ageing-Water-Storage-Infrastructure-An-Emerging-Global-Risk.pdf
Mullaperiyar Dam, Periyar River, Kerala, India. Age: 125 years
The Mullaperiyar Dam is a gravity dam of 53.6 m in height and a reservoir capacity of 443 million m³. It impounds the Periyaru River in Kerala State, downstream to Tamil Nadu state, India. It was built in 1895 by the British government to provide irrigation and eventually began to generate power in 1959 (Chowdhury, 2013; Thatheyus et al., 2013). At the time of construction, the dam had an intended lifespan of 50 years (Chowdhury, 2013). Still, in service over a century later, the dam shows significant structural flaws and may be at risk of failure. The dam is located in a seismically active area. A minor earthquake caused cracks in the dam in 1979 (Rao, 2018), and in 2011, more cracks appeared in the dam due to seismic activity (Thatheyus et al., 2013). Leaks and leaching are also concerning, as the methods and materials used during construction are considered outdated compared to current building standards. In response to these structural issues, dam decommissioning has been considered. However, a conflict between Kerala and Tamil Nadu States started to grow regarding the best way to manage this ageing infrastructure (Thatheyus et al., 2013). Although the dam is located in Kerala, it is operated by the upstream state of Tamil Nadu. Kerala residents are afraid of a dam collapse and argue that the reservoir level must be lowered until the dam is fixed. Meanwhile, Tamil Nadu residents want to maintain the water levels at capacity (Rao, 2018). In 2009, Kerala requested a new dam to be built, but Tamil Nadu opposed the idea. Currently, the decision of how to manage the ageing Mullaperiyar dam is hotly debated and working through the court system. A dam failure risk would be catastrophic: nearly 3.5 million people will be affected (Chowdhury, 2013).
Related studies
Chowdhury, A. R. (2013). Decommissioning dams in India: a comparative assessment of Mullaperiyar and other cases. Development in Practice, 23(2), 292–298. https://doi.org/10.1080/09614524.2013.772563
Rao, S. (2018). Explainer: Why Kerala and Tamil Nadu have fought for decades over the Mullaperiyar dam. Scroll.In. Retrieved October 18, 2020, from https://scroll.in/article/864687/explainer-why-kerala-and-tamil-nadu-have-fought-for-decades-over-the-mullaperiyardam
Thatheyus, A., Dhanaseeli, D. P. , & Vanitha, P. (2013). Inter - State Dispute over Water and Safety in India: The Mullaperiyar Dam, a Historical Perspective. American Journal of Water Resources, 1(2), 10-19 http://pubs.sciepub.com/ajwr/1/2/2/
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