New Delhi, Feb. 5: It took nearly 17 years, 577 sittings and meetings with 17 experts, but finally the Cauvery Water Disputes Tribunal may have got its math right.

After deliberations longer than the Bombay blasts trial — and an inter-state conflict that outlasted nearly a dozen chief ministers and witnessed ethnic riots — Karnataka and Tamil Nadu today learnt what their shares in the river’s waters would be.

So did Kerala and Puducherry, minor players in a battle of attrition that has locked their bigger neighbours since the 19th century.

As Tamil Nadu rejoiced, Karnataka quickly injected some uncertainty, deputy chief minister B.S. Yediyurappa telling the Assembly a review would be sought.

Tamil Nadu has been allocated 419 tmc ft (thousand million cubic feet) and Karnataka 270 tmc ft of the total usable water in the Cauvery, which the tribunal put at 740 tmc ft. Kerala and Puducherry get 30 and 7 tmc ft.

That leaves out 14 units, some of it reserved “for environmental protection” while the rest escapes into the sea.

Upstream Karnataka will, however, release only 192 tmc ft for Tamil Nadu, of which 10 tmc is reserved for environmental protection. The rest of Tamil Nadu’s allocation of 419 units is generated in the state itself: for instance, from rain or tributaries.

Karnataka will not be gloating that it has 13 units less to part with than the 205 tmc ft it now releases under an interim order. In reality, it will be giving up more, because the point at which the flow is to be measured has been moved upstream to Billigundulu gauge.

Some 25 tmc ft is believed to be generated in Karnataka between the gauge and the earlier point of measurement at Mettur.

While Tamil Nadu’s leaders and farmers celebrated the end to “mental torture”, stemming from Bangalore repeatedly turning off the tap, security forces were being rushed to the Karnataka capital and its Cauvery delta districts.

In 1991, Karnataka had rejected the interim award. It had brought an ordinance to protect the water but the apex court, approached by the President for clarification, had declared it unconstitutional.

When the Centre gazetted the interim award, the state government called a bandh and ordered schools closed while pro-Kannada rioters targeted Tamil residents for days. Tamil Nadu responded with its own bandh and rioting.

Today, Karnataka chief minister H.D. Kumaraswamy urged people to stay calm and called an all-party meeting.

The tribunal has ordered a regulatory authority set up to monitor the monthly release for five years. After that, the flow can be modified without changing the annual (June 1 to May 31) allocation.

If the National Hydro-Power Corporation starts any project on the Cauvery, it must see that the pattern of downstream release did not change.

The tribunal had been formed in June 1990 on a request from Tamil Nadu, which said Karnataka was violating the water treaties of 1892 and 1924, between the Maharajah of Mysore and Madras Presidency, by building dams.

Karnataka argued the agreements were no longer valid, but the tribunal rejected this. It said the 1924 pact provided for a review after 1974 and that is what it was doing.