Mullaperiyar Dam

It is a masonry gravity dam on the confluence of Periyar River and Mullayar River in the Indian state of Kerala.
It is located 881 m above mean sea level, on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala.
It is operated and maintained by the neighbouring state of Tamil Nadu. Even though, the dam is located in Kerala.
The dam is operated by Tamil Nadu following an 1886 lease agreement for 999 years. It was signed between the Maharaja of Travancore and the Secretary of State for India during British Rule.
In the 1970s, the lease agreement was renewed by Tamil Nadu and Kerala. It gave the former, rights to the water from the dam, besides the authority to develop hydropower projects at the site. In return, Kerala receives rent from Tamil Nadu.

Why Controversy over Mullaperiyar dam then?

In 1979, problems erupted over the safety of the Mullaperiyar dam. It was claimed that a minor earthquake had resulted in the cracks in the dam.
Consequently, the Central Water Commission decided that water level in the dam be brought down from the full reservoir level of 152 ft to 136 ft. It will enable Tamil Nadu to carry out dam strengthening works.
By the 1990s, Tamil Nadu started demanding restoration of the water level in the Mullaperiyar dam as it completed the task assigned to it. They approached the Supreme Court when no consensus was reached through negotiations.
In 2014 as per directions of the Supreme Court, the Ministry of Jal Shakti constituted a three-member Supervisory Committee.