Explained | What is the controversy over Mullaperiyar?

Are there safety issues about water levels at the 126-year-old dam? How have Kerala and Tamil Nadu responded to the situation?

Updated - October 31, 2021 10:53 am IST

Published - October 31, 2021 02:04 am IST

Water woes: The 2018 floods in Kerala and the erratic monsoons have put the 126-year-old dam in the spotlight.

Water woes: The 2018 floods in Kerala and the erratic monsoons have put the 126-year-old dam in the spotlight.

The story so far: Coinciding with an episode of erratic, cataclysmic rain in Kerala’s high-ranges, the Supreme Court last week considered a public interest litigation petition filed by a Kerala physician and two former local body representatives on the operation of the Mullaperiyar dam over which Kerala and Tamil Nadu have been sparring for long. With the threat of floods looming large and the reservoirs filling up, the court asked both States to abide by the rule curve for the period set by the Supervisory Committee constituted at its instance. Accordingly, the water level in the dam would be limited to 138 feet till October 31 and 139.5 feet till November 10. The court will hear the case again on November 11.

What is the status now?

Three shutters of the dam were opened on October 30 to release water . While people living downstream were evacuated beforehand, water release from the Mullaperiyar dam did not alter the level in the much larger Idukki reservoir, at over 94% of its storage capacity, located 35 km downstream.

Why is Mullaperiyar dam a sore point?

The Maharaja of Travancore signed a 999-year Periyar Lake lease agreement with the British government on October 29, 1886, for the construction of the Mullaperiyar dam across the Periyar in the present Idukki district. The dam became a reality nine years later. The water supplied from it through a tunnel to the water-scarce southern region of Tamil Nadu, especially the Vaigai basin, would be the lifeline for farmers of Theni, Dindigul, Madurai, Sivaganga and Ramanathapuram districts. On an average, 22 thousand million cubic feet (tmc ft) of water is diverted, irrigating about 2.20 lakh acres and meeting the drinking water requirements of people in the region. Concerns over the safety of the gravity dam built using lime-surkhi (burnt brick powder) mortar came to the fore in 1979. In November that year, a tripartite meeting chaired by the then chairman of the Central Water Commission (CWC), K.C. Thomas, decided that the level had to be brought down from the full reservoir level of 152 feet to 136 feet to enable Tamil Nadu, which owns and maintains it, to carry out dam strengthening works. By the mid-1990s, Tamil Nadu started demanding restoration of the level.

What happened in the legal battles?

The Central Government set up an expert committee in 2000 to look into the dam's safety. The committee recommended raising the level to 142 feet, which was endorsed by the Supreme Court in February 2006. Kerala sought to restrict the level to 136 feet by way of an amendment to the Kerala Irrigation and Water Conservation Act, prompting the Tamil Nadu Government to move the Supreme Court. In February 2010, the court constituted an empowered committee to study the whole gamut of issues concerning the dam. Based on the committee’s finding that the dam was “structurally and hydrologically safe”, the court, in May 2014, struck down Kerala’s Act and allowed Tamil Nadu to maintain the level at 142 feet. It also asked the Central Government to set up a three-member Supervisory Committee to monitor dam safety.

Why is it a social issue?

Commissioned by the Kerala Government in the latter part of the 2000s, a study by IIT-Roorkee raised questions about the survival of the dam, located in seismic zone-3, in the event of an earthquake of a fairly high magnitude. A series of tremors felt in the area in 2011 caused alarm. Subsequently, the floods of 2018 and the erratic nature of annual monsoons ever since brought the focus back on the 126-year-old dam.

Why is the case in the Supreme Court again?

Joe Joseph, a doctor who was the candidate of the corporate-backed Twenty20 in the recent Kerala Assembly election from Kothamangalam, downstream of the Mullaperiyar and Idukki dams, moved the court, along with two others, last year contending that the Supervisory Committee had abdicated its responsibilities to a sub-committee constituted at the direction of the court for water management in the dam. They also urged the court to ask the CWC to fix the ‘rule curve’, ‘instrumentation scheme’ and ‘gate operation schedule’ of the dam. Massive landslides had devastated the hilly regions in central Kerala and weather prediction was ominous when the court’s attention was drawn to a report prepared by the United Nations University-Institute for Water, Environment and Health, which cited “significant structural flaws” in the dam and said it “may be at risk of failure”. “Leaks and leaching are also concerning, as the methods and materials used during construction are considered outdated, compared to the current building standards,” it said.

The Kerala Government, a respondent, argued for lowering the full reservoir level to 139 feet as the ageing dam was in a ‘deteriorating condition’. In the event of a dam failure, it would result in unfathomable human tragedy and submitted a case for decommissioning the dam, in whose place a new dam could be built to cater to Tamil Nadu's water needs. However, Tamil Nadu, relying on the Supreme Court’s two judgments, has been opposing any suggestion for lowering the level from 142 feet, apart from rejecting the idea of a new dam. It says it is taking steps to complete the remaining works to strengthen the dam, including those meant for the ‘baby dam,’ situated alongside the main dam, for which clearances from the Kerala and Central Governments are required.

What’s on the cards?

Design of a new dam by Kerala’s Irrigation Design and Research Board is in the final stages . However, without Tamil Nadu on board, this is not going to be a reality. Meanwhile, in the backdrop of bad weather forecast, Kerala Chief Minister Pinarayi Vijayan wrote to his Tamil Nadu counterpart M.K. Stalin, urging him to draw maximum quantum of water from the dam through the tunnel so that a large volume release would be avoided altogether. Assuring Mr. Vijayan of all support, Mr. Stalin informed him that the level in the dam was being closely monitored and the current storage was well within the level permitted by the Supreme Court. A meeting between the Chief Ministers to discuss the issue is being planned in December.

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