With Kerala maintaining that increasing the water level in the Mullaperiyar dam beyond 136 ft will endanger the structure’s safety during maximum flood level, the Supreme Court on Wednesday asked the State to provide sufficient data to prove its point.

A five-Judge Constitution Bench, comprising Justices D.K. Jain, B. Sudershan Reddy, Mukundakam Sharma, R.M. Lodha and Deepak Verma, is hearing Tamil Nadu’s suit questioning the law enacted by Kerala to prevent raising the water level in the dam beyond 136 ft.

Kerala’s senior counsel Harish Salve explained the objects and reasons for enacting Kerala Irrigation and Water Conservation (Amendment) Act, 2006.

He said there were reports to suggest that if the water level was raised to 142 ft, then during the stage of Probable Maximum Flood (PMF) level, the water would touch 160 ft (despite spillways), over and above the parapet, endangering the dam’s safety.

At this stage, Justice Lodha told counsel, “There had been severe floods in 1924, 1943 and 1961 and the dam withstood the maximum floods; only in 1961 the water level touched 152.35 ft. This would show that even during maximum floods, the level did not touch the contour line of 155 ft. All these figures were available at that time.

“This court has already examined the dam’s safety up to 142 ft and had come to a conclusion. Your contention therefore is unfounded, misconceived and fallacious, nothing but jugglery of words and figures. You give us figures how it will affect the dam.”

Mr. Salve said that on Thursday he would present the figures of water overflow during PMF from the level of 136 ft.

Justice Jain sought to know from Mr. Salve why Kerala in its reply had stated that in case of water spillover from the dam at the maximum flood level, the submergence area would exceed the area in the lease agreement.

Mr. Salve replied: “Flood routing studies have revealed that backwater formation or spread will cross 155 ft and reach up to 157.7 ft submerging the lands which are not part of the lease land. As per the lease, Tamil Nadu cannot store water beyond the contour line of 155 ft.”

He said: “The dam will overflow even with a PMF of 2.12 lakh cusecs and as such the level of submergence will exceed the lease area. Further, the dam will be hydrologically unsafe and that is our concern.”

Even as Mr. Salve was defending the law, Justice Sharma said: “Today you are restricting the height to 136 ft. As we see that under the Act, the Dam Safety Authority has wide powers, including de-commissioning the dam. Tomorrow, if you decide to de-commission the dam, we are more worried about that. Whether you [Kerala] will go that extent or not, we are putting to a practical situation.”

Mr. Salve agreed that the DSA had ample powers even to de-commission the dam in the interest of public safety.