The Supreme Court has directed the Supervisory Committee to take an immediate and firm decision on the maximum water level that can be maintained at Mullaperiyar dam amidst torrential rains in Kerala.

What is the news?

• A report by United Nations has stated that the Mullaperiyar dam, situated in a seismically active area, faces the risk of failure.
• Earlier this year, the Supreme Court warned the TN Chief Secretary against the failure to give information on the rule curve for dam which decides the discharge of excess water.

Mullaperiyar Dam

• It is a masonry gravity dam on the Periyar River in Kerala.
• It is located on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District.
• It was constructed between 1887 and 1895 by John Pennycuick and also reached in an agreement to divert water eastwards to the Madras Presidency area.
• It has a height of 53.6 m (176 ft) from the foundation, and a length of 365.7 m (1,200 ft).

Operational issue

• The dam is located in Kerala but is operated and maintained by Tamil Nadu.
• The catchment area of the Mullaperiyar Dam itself lies entirely in Kerala and thus not an inter-State river.
• In November 2014, the water level hit 142 feet for first time in 35 years.
• The reservoir again hit the maximum limit of 142 feet in August 2018, following incessant rains in the state of Kerala.
• Indeed, the tendency to store water to almost the full level of reservoirs is becoming a norm among water managers across States.

The dispute: Control and safety of the dam

• Supreme court judgment came in February 2006, has allowed Tamil Nadu to raise the level of the dam to 152 ft (46 m) after strengthening it.
• Responding to it, the Mullaperiyar dam was declared an ‘endangered’ scheduled dam by the Kerala Government under the disputed Kerala Irrigation and Water Conservation (Amendment) Act, 2006.
• For Tamil Nadu, the Mullaperiyar dam and the diverted Periyar waters act as a lifeline for Theni, Madurai, Sivaganga, Dindigul and Ramnad districts.
• Tamil Nadu has insisted on exercising the unfettered colonial rights to control the dam and its waters, based on the 1886 lease agreement.

Rule of Curve issue

• 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.
• The TN government often blames Kerala for delaying the finalization of the rule curve.

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