Background of the Dispute

• The Maharaja of Travancore signed a 999-year Periyar Lake lease agreement with the British government in 1886, for the construction of the Mullaperiyar dam across the river Periyar in the present Idukki district of Kerala. The reservoir is within the Periyar Tiger Reserve. 
• The water supplied from the dam 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, 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 including the Central Water Commission (CWC) 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 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 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 Supreme Court, in 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 in News?

• Tamil Nadu has accused Kerala in the Supreme Court of “crying foul” about the safety of the over 125-year-old Mullaperiyar dam while at the same time “wilfully obstructing” work essential to maintain the structure. 
• It contended that Kerala has managed to delay even routine annual maintenance works, including painting, patch works, repair to staff quarters, etc., for two months to more than a year. 

https://www.thehindu.com/news/national/tamil-nadu-moves-supreme-court-accuses-kerala-of-obstructing-work-on-mullaperiyar-dam-while-crying-foul-about-its-safety/article68142173.ece