No state can claim exclusive right to a river passing through different states, said three judges of the Supreme Court including Chief Justice Dipak Misra.

"Drinking water has to be kept on the highest pedestal," said the court, acknowledging Bengaluru's needs as a "global city" and allotting it 4.75 TMC for drinking water out of Karnataka's increased share.

Reducing Tamil Nadu's share, the Supreme Court said the state's irrigation area had not been assessed correctly and its government had not considered the availability of ground water.

In Tamil Nadu's share, 10 TMC of the 20 TMC groundwater beneath the Cauvery basin can be accounted for, the judges said. The Chief Justice said the 2007 tribunal allocation of 30 TMC to Kerala and 7 TMC to Puducherry remains unchanged.

Many disappointed farmers in Tamil Nadu said the cut in the state's share would reduce cultivation by one lakh acre.

In hearings that ended last year, Tamil Nadu had asked the Supreme Court to make a "fundamental change" in the water sharing pact and set up a Cauvery Management Board. "The river is perennial, but the litigation should not be," Tamil Nadu's lawyer Shekhar Naphade had told the court.

Karnataka argued that it was unfair to require the state to release a fixed amount of water irrespective of the availability of water. "It is like the tribunal ordering god to send rain to the State," said Fali Nariman, representing Karnataka. The water tribunal which delivered the 2007 award was set up in 1990 on the orders of the Supreme Court.

The 765-km long Cauvery river, also called the Ganga of the south, is the lifeline for Karnataka and Tamil Nadu. The river originates in Kodagu district in southern Karnataka and flows into Tamil Nadu, Kerala and Puducherry.

The appeal was filed against the 2007 order of the Cauvery Water Tribunal that allocated, in a normal year, 270 TMC, or thousand million cubic feet, 192 TMC to Tamil Nadu at its Mettur Dam, 30 TMC to Kerala and 6 TMC to Puducherry. Karnataka wanted Tamil Nadu's share to be slashed by half and had made a strong case on drinking water needs of Bengaluru and Mysuru.