Cauvery is a 800-km long river that originates in Karnataka, flows through Tamil Nadu and exits into the Bay of Bengal. Its catchment area is in Kerala and Puducherry also. All four states lay claim to its waters. Karnataka, being the state from which the water flows out, is held responsible to release adequate water to all the other three states. In a regular monsoon year, the water just flows down to all the others and there is no dispute at all. In rain-deficit years, the water has to be shared.Karnataka and Tamil Nadu have claims and counter-claims on how this should be done.
The dispute is nearly 125 years old. Till 1990, the issues were sorted through earlier agreements and talks between the states. In 1990, the V P Singh government set up the Cauvery Water Disputes Tribunal, which gave a strongly-disputed interim order in 1991. In 2007, after exhaustive discussions, the Tribunal gave a final order allocating 419 thousand million cubic feet (TMCFT) to Tamil Nadu, 270 TMCFT to Karnataka, 30 TMCFT to Kerala and 7 TMCFT to Puducherry , on the premise of 740 TMCFT at 50 per cent dependability in the Cauvery . A TMCFT is equal to water released at the rate of 11,000 cusecs (cubic feet per second) for a day or 2,831.7 crore litres of water.
Tamil Nadu approached the Supreme Court for 50 TMCFT of water for its samba crop, cultivated from August to January. Karnataka, as per the Tribunal order, has to release 10 TMCFT in June, 34 in July, 50 in August and 40 in September, but had released only 33 TMCT from June. Karnataka pointed to deficit pre-monsoon showers (38 percent) and deficit rainfall in Cauvery catchment areas leading to a total deficit of 48 percent in inflows to the reservoirs. The state said it needs about 30 TMCFT of drinking water for Bengaluru, Mysuru, Mandya cities, 48 towns and 630 villages in the basin, besides about 47 TMCFT for its standing crop on 6.91 acres, about half of the usual rabi cultivation area of 14 lakh acres. Supreme court on September 5 directed the state to release about 13 TMCFT to Tamil Nadu and another 4 TMCFT on September 12, bringing the water storage in the state's reservoirs to 26 TMCFT, lesser than the amount needed to meet drinking water needs up to May 2017. On September 19, the Cauvery Supervisory Committee set up by the Supreme court said Karnataka should release another 2.72 TMCFT upto September 30, which was revised by the apex court's bench on September 20 and hiked to 3.82 TMCFT up to September 27, when the next hearing is scheduled.
Chief minister Siddaramaiah has said the latest Supreme Court order is not implementable.Three times in the recent past, Karnataka has been directed by the Supreme court to release water from its four reservoirs in the Cauvery basin to Tamil Nadu, despite water shortage. In 1995, then Prime Minister P V Narasimha Rao convened a meeting of the CMs and opposition leaders of Cauvery basin states and asked Karnataka to release a total of 6 TMCFT, which the state complied with. In 2002, the apex court asked Karnataka to release 0.8 TMCFT a day for the entire season, , which then CM S M Krishna said was not possible. He was hauled up for contempt of court and forced the release the water.
From September5 to 11, Bengaluru Mysuru highway which runs through Cauvery basin saw a total blockade on traffic; all traffic between Karnataka and Tamil Nadu has also been stopped since September 5. Bengaluru city saw a bandh on September 9 and arson incidents on September 12, where two persons died.. ASSOCHAM put total losses due to crisis at Rs 25,000 crore. Tamil Nadu saw a bandh on September 16. Police in Karnataka and Tamil Nadu have escorted vehicles to each other's borders to prevent further violence.