According to the Supreme Court statement, the Tamil Nadu Chief Secretary shall be “personally responsible” and “appropriate action” will be taken on failure to give information on the rule curve for Mullaperiyar dam to the Supreme Court-appointed Supervisory Committee.
A rule curve or rule level specifies the storage or empty space to be maintained in a reservoir during different times of the year. It decides the fluctuating storage levels in a reservoir.
The gate opening schedule of a dam is based on the ‘rule curve’. It is part of the “core safety” mechanism in a dam. Rules curves are used to guarantee the safety of the reservoir as well as water security.
Located in kerala, the Mullaperiyar dam is 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. The Dam is located on the confluence of the Mullayar and Periyar rivers in Kerala’s Idukki district. The dam is located on the Cardamom Hills of the Western Ghats.
The dam was built in the late 1800s in the princely state of Travancore (present-day Kerala) and given to British-ruled Madras Presidency on a 999-year lease in 1886.
The agreement granted full rights to the secretary of state of Tamil Nadu, a British official, to construct irrigation projects on the land. The dam was built to divert eastwards a part of the west-flowing Periyar river, to feed the arid areas of Tamil Nadu.
The agreement was renewed by the two state governments in independent India in the 1970s. Tamil Nadu was given rights to the land and the water from the dam as well as the authority to develop hydro-power projects at the site, and Kerala would receive rent in return.
Tamil Nadu claims that though it has undertaken periodic repairs on the dam, the Kerala government has not allowed it to raise the water level. It says it has suffered huge losses from not being able to use the dam to its full capacity.
Kerala, on the other hand, contends it is not safe to raise the water level as Idukki district, where the dam is located, is earthquake-prone and has experienced multiple low-intensity quakes.
Scientists, too, have said the dam cannot withstand an earthquake measuring over six on the Richter scale and that if such a calamity were to happen, the lives of more than three million people would be imperilled.
The divergent views resulted in the two states moving their high courts and multiple petitions being filed. In 2000, the matter reached the Supreme Court, where it has been hotly contested for years.
In 2006, the Supreme Court allowed the Tamil Nadu government to raise the water level to 142 feet, contending that the apprehensions raised by Kerala were baseless.
The Kerala government countered this with an amendment to the 2003 Kerala Irrigation and Water Conservation Act.
The amendment classified the Mullaperiyar dam as endangered and restricted the level of water in it to 136 feet. Tamil Nadu responded by moving the Supreme Court, calling for the amendment to be struck down as unconstitutional.
