Policemen on vigil in Bangalore. (PTI)

What is the dispute about?

It’s about sharing of the Cauvery waters by Karnataka and Tamil Nadu, with Kerala and Puducherry the minor stakeholders. As the river originates in Karnataka’s Coorg, the dispute revolves round how much water Karnataka must release for Tamil Nadu’s farmers.

When did it start?

Over a century ago, prompting two treaties between the then Madras Presidency and the Maharajah of Mysore in 1892 and 1924. Two years before the second expired in 1974, the two chief ministers met and decided not to take up any new dams or irrigation projects.

When did the current round begin?

In July 1986, Tamil Nadu asked the Centre to refer the dispute to a tribunal. This was followed by a farmers’ association in Tamil Nadu moving the Supreme Court. The state impleaded itself in the case.

Then why did a solution take so long?

Because every time the tribunal came up with an answer, Karnataka threw a spanner in the works. There were street riots, suicides, or outright refusal to comply with the award. Once it even brought in an unconstitutional law to hold on to the water.

Didn’t the Centre or Supreme Court intervene?

They repeatedly prodded the two chief ministers to meet. Sometimes they did, sometimes they wouldn’t. It never came to anything. It was after a series of failed patch-up efforts that the tribunal was set up in June 2, 1990.

What did the tribunal do?

It started off fine, ordering an interim relief of 205 tmc ft to Tamil Nadu in June 1991. Tamil Nadu was to release 6 tmc ft to Puducherry (then Pondicherry).

Why did it fail?

Karnataka rejected the order and asked the Centre to stay the tribunal’s proceedings. Then the S. Bangarappa-led government issued an ordinance to protect the water.

Was the ordinance legal?

That’s what an alarmed President Venkataraman asked the Supreme Court. The court clarified in November 1991 that the ordinance was unconstitutional and upheld the tribunal’s interim award.

What happened next?

Politics and violence. First Bangarappa called a bandh and asked schools to close for 10 days. Ethnic riots targeted Tamils from December 24 to 27. The Tamil Nadu government replied with a bandh on December 27, which saw retaliatory arson and looting.

Was any compromise reached?

In April 1992, the tribunal “clarified” that “no undue hardship” should be caused to Karnataka while ensuring the release of 205 tmc ft. This was followed by a decade of peace as there was good rainfall and Karnataka was able to release the water.

What spoiled it?

In 2002, Karnataka chief minister S.M. Krishna stopped releasing the water after a drought. In September, he backed down under pressure from the Supreme Court and Centre. But a Karnataka farmer jumped into a river in protest and drowned, and Karnataka turned the tap off again. Krishna took out a padayatra from Bangalore to Mandya to show solidarity with the farmers.

Did Tamil Nadu take it lying down?

No, it dragged Krishna to court for contempt. Krishna apologised but Mandya MP M.H. Ambareesh, then Union information minister, resigned in protest.

Were there any more hitches?

Yes, the tribunal was to deliver the award in mid-2006 but felt it needed more information on water requirement and crop pattern. It asked the Centre to appoint an assessor committee. Karnataka rejected the assessors’ report.

The assessors had recommended Karnataka should get 250 tmc ft and Tamil Nadu, 395 tmc ft. The total river water was estimated to be 740 tmc ft.

What did the states want?

Tamil Nadu wanted 566 tmc ft, saying Karnataka needed only 175. Karnataka demanded 465 tmc ft, arguing Tamil Nadu required just 252.

Will the award make them happy?

Tamil Nadu is happy but Karnataka chief minister Kumaraswamy will not react before an all-party meeting. Security has been beefed up in Karnataka, with reinforcements sought from Andhra Pradesh and Maharashtra.