Explainer
Between 1960 and late 1980s, Karnataka built four dams on Cauvery – Hemavati, Harangi, Kabini and Suvarnavathy.
PTI

The cry of protesters ring across parts of Karnataka yet again. Effigies are burnt and road-rokos staged as political outfits together with farmers in the state refuse to share water from the Cauvery river with neighbouring Tamil Nadu.  

The Cauvery river

The Cauvery river originates in Kodagu in Karnataka, the river and its tributaries flow through Haasan, Mandya, Mysuru districts in Karnataka and Dharmapuri, Erode, Karur, Trichy, Cuddalore, Pudukottai, Nagapattinam, Thanjavur and other districts in TN. Many of these districts are dependant on Cauvery water for irrigation. Bengaluru city gets its water from the Cauvery.

A brief history of the tussle

A water sharing agreement was signed between the Madras Presidency and Princely State of Mysore in 1924. It lapsed in 1974.

Between 1960 and late 1980s, Karnataka built four dams on Cauvery – Hemavati, Harangi, Kabini and Suvarnavathy.

This put Tamil Nadu, the lower riparian state, already dependent on Karnataka to release water from the river to keep its irrigation steady, in a precarious situation. TN approached Supreme Court.

SC directed the central government to constitute the Cauvery Water Dispute Tribunal (CWDT) in May 1990.

In June 1991, CWDT gave an interim award and asked Karnataka to release 205 tmc feet to TN every year, then riots followed.  

This timeline recounts what happened from 1990 to 2013; but the long and short of it – Karnataka would often release less water to Tamil Nadu, saying that there wasn’t enough in the state's reservoir and that the Karnataka needed water for its own use.

In 2007, CWDT gave its final order. Of the total available 740 tmc ft water, this was the allocation made:

Tamil Nadu - 419 tmc ft

Karnataka - 270 tmc ft

Kerala - 30 tmc ft

Puducherry - 7 tmc ft

Apart from this, 10 tmc ft was demarcated for environmental purposes and 4 tmc ft which would inevitably run off into the sea.

According to this award, Karnataka was mandated to release 192 tmc ft of water to Tamil Nadu every year. The order specifies how much water Karnataka had to release every month. For example, in the month of August, Karnataka has to give Tamil Nadu 50 tmc feet of water.

Why the protest this year

The agitations this year started after Karnataka declared that it cannot release water to TN due to a deficit leading to the intervention by the apex court. Karnataka had said it has a deficit of about 80 tmc ft in its four reservoirs.

Crop seasons

Tamil Nadu has three crop seasons Kuruvai (April to July), Samba (August to November) and Navarai (December to March).

Karnataka follows the crop seasons like Northern India does that consists of Kharif (May to August), Rabi (September to December) and Summer crop (January to May).

The Cauvery issue props up when the southwest monsoon that Karnataka is dependent on fails. The north-east monsoon hits Tamil Nadu around October but prior to that, it must rely on Karnataka for the bulk of its water needs.

No clear distress management formula  

While the tribunal stated that in years of deficient rainfall, the total water be shared proportionally, this doesn’t happen. Both the states almost never sit down and discuss the amount of water they need and can spare.

Read:

Karnataka schools, colleges will shut for September 9 strike, Dasara break to be cut short?

What’s the point of bandhs if they don’t solve Cauvery issue? Vatal Nagaraj answers

As the state erupts in massive protests, Karnataka releases Cauvery water to Tamil Nadu

A beginner’s guide to what the Cauvery dispute is all about