In an affidavit filed by the Chief Secretary, the Kerala government said that as the water level crossed 137 feet at Mullaperiyar Dam, authorities in Kerala decided to evacuate on a war footing people who lived in the dam's downstream.

Of the total population of about 3.48 crore, more than 54 lakh or one sixth of the population of Kerala had been directly affected by the floods, said the affidavit.

The affidavit further said that in the wake of prior alerts by its engineers, Kerala's Water Resources Secretary had written to her counterpart in Tamil Nadu and the Chairman of the Supervisory Committee on Mullaperiyar dam requesting controlled release of water without waiting for the water level in the reservoir to reach its full level.

"Accordingly, the Tamil Nadu government was requested to gradually release water... But no positive assurance in this regard was received from Tamil Nadu even after repeated requests...

"But the sudden release from the Mullaperiyar dam, the third largest reservoir in the Periyar Basin, forced us to release more water from Idukki reservoir, downstream of Mullaperiyar, which is one of the causes of this deluge."

The Chief Secretary suggested that to avoid a repeat of such situations, the Supervisory Committee be headed by the Chairman of the Central Water Commission (CWC) with Secretaries of both the states as members and the panel should be empowered to take decisions by a majority opinion regarding operations during flood or similar crisis.

The Kerala government also sought a management committee to manage the day-to-day operations of the Mullaperiyar dam, to be headed by a chief engineer/superintending engineer of the CWC with both chief engineers/superintending engineers of the two states.

The Mullaperiyar reservoir, which is wholly situated in Kerala, in the upper reaches of the Western Ghats above Idukki reservoir, is operated by the Tamil Nadu government.

Some 370 people have died since the monsoon rains began on May 29 and 1 million people are still sheltered in relief camps after torrential rains and the opening of the sluice gates of dams led to the worst floods in Kerala in nearly a century.

On August 18, the top court had asked the Chief Secretary of Kerala to file an affidavit on what steps were being taken for disaster management, rescue and rehabilitation of those affected.

The court had suggested that the Disaster Management sub-committee, National Crisis Management Committee (NCMC) and the court-appointed committee should meet to explore the possibility of reducing the water-level in the Mullaperiyar dam reservoir there to 139 feet.

The court was hearing a PIL seeking directions for management of water in the Mullaperiyar dam reservoir and announcement of a disaster management plan in relation to the dam.

The petition was filed by Kerala resident Russel Joy, who also sought direction to Tamil Nadu to ensure proper management of water release from the dam so that no harm is caused to people living downstream.

The hearing on the plea is scheduled on Friday.