Debate over Mullaperiyar dam’s safety continues with opposing views in Kerala and Tamil Nadu

Though located geographically in Kerala, the 126-year-old Mullaperiyar Dam is owned, operated, and maintained by the Tamil Nadu government and has been a point of dispute between the two neighbouring states for decades. While Kerala maintains that the structure is weak and a new dam needs to be constructed in its place, Tamil Nadu has declared it as safe.

In a statement last month, speculated to be a political message to Kerala, the Tamil Nadu Chief Minister M.K. Stalin announced that the state would set up a statue of Colonel John Pennycuick, a British engineer instrumental in the construction of the dam, at a park at his hometown in the United Kingdom. This proposed statue, sponsored by the Tamil Nadu government, would be a token of gratitude for building the dam and diverting water from there to the arid villages and towns of the southern districts to address their drinking water and irrigation concerns.

While Tamil Nadu is turning the dam issue into a sentimental one evoking the memories of the British engineer, Kerala has been strongly advocating the need to decommission the “deteriorated” structure and build a new one, citing climate change-induced erratic and heavy rainfalls that could further damage the structure. political leaders of Kerala argue that the dam is a ticking time bomb that can explode at any moment, causing deaths of thousands in the state. It maintains that razing down the existing weak structure and constructing a new dam is the only solution.  Tamil Nadu meanwhile considers it as a safe and well-maintained dam and is making persistent efforts to raise the water storage level in it to 152 feet through interventions in Madras high court, Supreme Court, Central Water Commission, and other top bodies.

Now, in the last week of January, the Central Water Commission (CWC) informed the Supreme Court that a new review of the safety of Mullapperiyar is due. In a status report before the apex court, CWC said that no review on safety was taken place for the last 12 years. However, the same report quotes Empowered Committee constituted by the Supreme Court in 2010 that noted that Mullapperiyar was found to be safe in all respects, hydrologically, structurally, and seismically.

While Kerala is supporting the call for a fresh safety review by the CWC in its report, Tamil Nadu is using the same report to support its claim that the dam is safe and there is no need for its decommissioning.

In an affidavit before the Supreme Court, at the end of last year, Kerala said the extreme weather events like the recent torrential rains in Chennai and heavy downpour in central Kerala indicate the possibility of a dam collapse soon. It even referred to the Uttarakhand floods in February 2021 which wiped out a hydropower project in Chamoli.

Kerala’s Irrigation Minister Roshy Augustine, told Mongabay-India that the only permanent solution to currently weak dam is decommissioning the existing dam and constructing a new one in the downstream reaches. “Any cascading failure of Mullaperiyar and Idukki dam in the lower reaches would create a catastrophe unimaginable, and it would affect the life and property of over 50 lakh (half a million) people,” warned Augustine.

When contacted, Kerala’s water resources department secretary T. K. Jose said the state is attempting to convince Tamil Nadu and the Supreme Court by citing decommissioning of a similar 19th-century lime concrete structure in Australia, following seepage. “The Victoria dam in Australia was decommissioned in April 1990. A new dam has been constructed in its place, and the new dam is supplying drinking water to the city of Perth. We can undertake the same steps here,” he said, adding that the new dam would protect the interests of both the states.

To build or not to build a new dam?

While the political tussle between the states continues, environmental experts have raised concerns about the dam’s location, which is a Seismic Zone III area (moderate damage risk zone) and have also highlighted that there has been a change in the rainfall pattern in Idukki since 2018 which needs to be taken under consideration.

According to Hyderabad-based water expert S. Janakarajan, constructing a new dam in the same seismic zone is dangerous. Kerala needs to investigate the demand based on the emerging new realities. “Decommissioning and construction activities would happen in a seismic zone which comes within a tiger reserve, known for rich biodiversity. Given the experiences from different parts of the world, dam construction can heighten earthquake, landslide and rockfall threats. The huge human presence required for construction activities will kill the highly crucial Periyar Tiger Reserve surrounding Mullapperiyar,” he said. According to him, the best solution is constructing a few smaller storage structures in the five districts of Tamil Nadu and diverting the excess water from the dam to the storage. A decentralised storage facility can avert the situation of keeping vast amounts of water in the 19th-century lime concrete structure, he said, adding that that keeping reduced quantities of water and periodic maintenance can protect the dam for several decades.

According to wildlife biologist and known environmental crusader V. S. Vijayan, constructing a new dam is equal to handing over the same problems to a future generation that would occupy the same area. “There are technologies which facilitate the building of earthquake-resistant dams. However, constructing them is not advisable near fault lines. The environmental impact of the new dam would be huge on the reserve. The Gadgil Committee on the Western Ghats has recommended decommissioning all such old structures. Construction of large new dams is no more considered an environmentally sound proposition,” said Vijayan. “By building small storages in Tamil Nadu, that state can divert whatever the amount is entitled to without having any rift with Kerala. According to the experts, a chain of barrages can diffuse the prevailing tension between the two states,” he added.

According to environmentalists Sreedhar Radhakrishnan, the existing dam walls are plastered with rubble masonry to keep its core from high-level water pressure safely. The core of Mullaperiyar is built with hydraulic lime and turki, which is a concoction of crushed bricks, river sand, and a variety of sugar. This makes it the only dam of its kind in the world but also makes it difficult to assess the strength of the structure.

According to C.P. Rajendran, an adjunct professor with the National Institute of Advanced Studies in Bangalore and author of the forthcoming book, Earthquakes of the Indian Subcontinent, both Kerala and Tamil Nadu have done nothing to monitor dam deformation at Mullaperiyar using advanced techniques like satellite-based measurements.

“At present, we have very little dam deformation data in the case of Mullaperiyar. If the states could collect it in the last 20 years, we might evolve a huge database, and it might have been reviewed by experts from both India and outside to help us find a fitting solution. What the time requires is the creation of an independent group of experts jointly by the two states to check existing technical reports and collect and analyse dam deformation data to decide on the dam’s future stability prospects,” he said. “It will be a long-term programme by design. Still, it should be done based on the information and sound science,” he adds.

Banner image: The Mullaperiyar dam. Photo by Haris Muhammed.