Cauvery Water Dispute and the Cauvery Water Management Authority

The Cauvery Water Dispute is a long fight between Karnataka and Tamil Nadu (with Kerala and Puducherry also involved) over how to share the water of the river Cauvery (also spelled Kaveri). Karnataka is the upstream state, where the river starts and where much of its water is collected. Tamil Nadu is the downstream state, where the largest farm area depends on it.

The dispute was decided by a tribunal in 2007 and finally settled by the Supreme Court in 2018. Today a body called the Cauvery Water Management Authority (CWMA) makes sure the decided shares are actually released.

The river and its basin

The Cauvery rises at Talakaveri in the Brahmagiri range of the Western Ghats, in Kodagu (Coorg) district, Karnataka. It flows about 800 km east and south-east through Karnataka and Tamil Nadu and enters the Bay of Bengal at Poompuhar in Tamil Nadu.

• Its basin covers about 81,155 sq km. Roughly 54% of it lies in Tamil Nadu, 42% in Karnataka, 3.5% in Kerala and a tiny part in Puducherry (the Karaikal area).
• Main tributaries from the left (north) bank: Harangi, Hemavati, Shimsha, Arkavati. From the right (south) bank: Lakshmanatirtha, Kabini, Suvarnavati, Bhavani, Noyyal, Amaravati. The Kabini starts in Kerala's Wayanad, which is why Kerala is part of the dispute.
• Important structures: the Krishna Raja Sagar (KRS) dam near Mysuru in Karnataka; the Mettur dam (Stanley Reservoir) in Tamil Nadu; and the ancient Grand Anicut (Kallanai), built by the Chola king Karikalan. The rich Cauvery delta in Thanjavur is called the "rice bowl" of Tamil Nadu.
• Biligundlu, on the Karnataka–Tamil Nadu border, is the point where Karnataka's releases to Tamil Nadu are measured.

Why is there a fight at all?

The river gets its water mainly from the southwest monsoon (June to September), which falls heavily on Karnataka's and Kerala's hills. Tamil Nadu's delta also gets rain from the northeast monsoon (October to December). Both states want water at the same time for summer crops like paddy. Karnataka says it needs water for Bengaluru's drinking needs and for its own drought-prone farmers.

Tamil Nadu says its delta farmers have used this water for centuries and have a right to it. In a bad rain year, there is simply not enough for everyone.

Where did it come from?

• 1892 and 1924 agreements. Under British rule, the Madras Presidency and the princely state of Mysore signed agreements in 1892 and 1924. These limited what Mysore (today's Karnataka) could build upstream without Madras's consent. Some clauses of the 1924 agreement were to be reviewed after 50 years, in 1974.
• After 1974, Karnataka argued that the old agreements were unfair because they were signed between a colonial presidency and a dependent princely state. Tamil Nadu wanted them honoured. Talks failed.
• 1990: Tribunal set up. On a direction from the Supreme Court, the Centre set up the Cauvery Water Disputes Tribunal (CWDT) in June 1990 under the Inter-State River Water Disputes Act, 1956.
• 1991: Interim order. The tribunal asked Karnataka to release 205 tmc ft a year to Tamil Nadu. This led to protests and violence in both states.
• 5 February 2007: Final award. The tribunal divided 740 tmc ft of water: Tamil Nadu 419, Karnataka 270, Kerala 30, Puducherry 7, plus 10 for environmental flows and 4 for unavoidable flow into the sea. In a normal year, Karnataka was to release 192 tmc ft at Biligundlu. The award also upheld the 1892 and 1924 agreements.
• 19 February 2013: The Centre published the award in the Gazette of India, after a Supreme Court direction. From then it had the force of a Supreme Court decree.
• 16 February 2018: Supreme Court judgment. In State of Karnataka v. State of Tamil Nadu, a three-judge bench changed the shares.

What did the 2018 judgment decide?

• Karnataka's share rose by 14.75 tmc ft to 284.75. Tamil Nadu's fell to 404.25. Kerala (30) and Puducherry (7) were unchanged.
• The 14.75 came from two parts: 10 tmc ft because the tribunal had not counted the groundwater available to Tamil Nadu in the basin, and 4.75 tmc ft for drinking and domestic needs, including those of the whole of Bengaluru city.
• Karnataka must release 177.25 tmc ft at Biligundlu in a normal year (down from 192).
• The court said drinking water has the highest priority, and that a river is a national asset; no state can claim to own it.
• It said its allocation would hold for 15 years.
• It directed the Centre to frame a scheme to implement the award.

How does the system work today?

On 1 June 2018, the Centre notified the Cauvery Water Management Scheme under Section 6A of the Inter-State River Water Disputes Act, 1956. It created two bodies:

• Cauvery Water Management Authority (CWMA): the main body, with its headquarters in New Delhi. It has a chairperson, two full-time members, two part-time members from the Central government, and four part-time members, one from each basin state (Karnataka, Tamil Nadu, Kerala, Puducherry). It has been under the Ministry of Jal Shakti since April 2020.
• Cauvery Water Regulation Committee (CWRC): a nine-member technical committee based in Bengaluru. It watches day-to-day reservoir levels, inflows and outflows and recommends how much water must be released.

Karnataka's normal-year releases at Biligundlu follow a monthly schedule, for example 9.19 tmc ft in June, 31.24 in July, 45.95 in August, 36.76 in September and 20.22 in October. In a distress year, when rainfall is poor and total water falls below normal, the shares of all states are reduced proportionately. Think of it like a family budget: if the family income falls by a fifth, every member's pocket money is cut by a fifth.

India's position and related flashpoints

• Mekedatu project: Karnataka plans a balancing reservoir of about 67 tmc ft at Mekedatu, in Ramanagara district, mainly for Bengaluru's drinking water and power. Tamil Nadu opposes it, saying it would reduce flows downstream. In November 2025 the Supreme Court called Tamil Nadu's plea against it premature, because expert bodies still have to examine the project report.
• Distress years such as 2016 and 2023 saw protests and bandhs in both states, showing how quickly water becomes an emotional issue.

Commonly confused concepts

• CWDT vs CWMA: The Tribunal (CWDT) decided the shares. The Authority (CWMA) implements them. The CWRC is the CWMA's technical arm for daily monitoring.
• Allocation vs release: Karnataka's allocation (284.75 tmc ft) is how much it may use. The release (177.25 tmc ft at Biligundlu) is how much it must let flow into Tamil Nadu in a normal year. These are different numbers.
• Cauvery vs Krishna vs Mahadayi disputes: The Krishna dispute is between Maharashtra, Karnataka, Telangana and Andhra Pradesh. The Mahadayi (Mandovi) dispute is between Goa, Karnataka and Maharashtra. Only the Cauvery involves Kerala and Puducherry.
• Mullaperiyar vs Cauvery: Mullaperiyar is a separate Tamil Nadu–Kerala dispute about a dam on the Periyar river, based on an 1886 lease.

Issues, criticism and the way forward

• No clear distress formula. "Proportionate reduction" sounds simple, but states argue over how to measure distress month by month and how to account for the northeast monsoon, which mainly helps Tamil Nadu.
• Climate change. Monsoons are becoming more erratic. An allocation based on average past flows may not match future rainfall.
• Groundwater and crop choice. Water-hungry crops like paddy and sugarcane in both states raise demand. Experts suggest better irrigation methods (drip and sprinkler), crop shifts and better groundwater management.
• Political heat. Every dry year brings protests, which makes calm technical decisions harder.
• Way forward: Experts suggest real-time data sharing, a scientific distress-sharing formula agreed in advance, basin-level planning that treats the river as one system, and building trust through the CWMA rather than through repeated court cases.

Concepts to Know

• tmc ft (thousand million cubic feet): A unit for large amounts of water. One tmc ft is about 28.3 billion litres, enough to fill roughly 11,000 Olympic swimming pools.
• Upstream and downstream states: The upstream state is where a river starts or flows first. The downstream state gets the water after it. Upstream states can control flow by building dams.
• Tribunal award: The final decision of a special water tribunal. Once published in the Gazette, it is binding like a Supreme Court decree.
• Distress year: A year in which rainfall and river flow are well below normal, so every state's share is cut in proportion.
• 50% dependability: The amount of water the river is expected to give in at least half of all years. The 740 tmc ft total is based on this measure.