Cauvery Water Shortfall: Tamil Nadu's Backlog Claim and the Supreme Court Hearing
The southwest monsoon (June to September) was weak this year in the Cauvery basin. When rain fails, there is less water to share, and that is the main reason for the new round of dispute between Karnataka (the upstream state) and Tamil Nadu (the downstream state).
Tamil Nadu told the Supreme Court that Karnataka has not released its due share of water at Biligundlu, the measuring point on the Karnataka-Tamil Nadu border. It said the backlog (water due but not released) was about 21 TMC (thousand million cubic feet) on 12 August 2026 and about 15 TMC on 7 October 2026. It said it had received about 46 TMC by 7 October.
Tamil Nadu argued that in a deficit year, the shortfall must be shared pro rata (in proportion to each state's share), that rain shortage in Karnataka's catchment does not justify holding back water, and that its standing crops need water now.
Karnataka replied that it faces severe distress, that it has released water as directed, and that the Cauvery Water Management Authority (CWMA) and the Cauvery Water Regulation Committee (CWRC) are expert bodies that should decide day-to-day releases.
On 8 October 2026, the CWMA directed Karnataka to ensure 3,000 cusecs at Biligundlu for 15 days from 9 October. Tamil Nadu asked the CWMA to revise this upward, calling it inadequate.
The Supreme Court heard the matter on 12 October 2026 and reserved its order (meaning it will give its decision later). Earlier, in August, the Court had told Karnataka to follow the CWMA's directions.
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 Cauvery river. The river rises in Karnataka and flows into Tamil Nadu, so the upstream state controls the flow that the downstream state depends on. A tribunal decided the shares in 2007, the Supreme Court changed them slightly in 2018, and a permanent body, the CWMA, now makes sure the shares are followed.
The failed southwest monsoon turned 2026 into a distress year, so Tamil Nadu and Karnataka disagree on how big the backlog is. Tamil Nadu wants the Supreme Court to order release of about 15 TMC, while Karnataka wants the CWMA's expert directions, such as the 3,000 cusecs order of 8 October, to decide releases.
Article 262 and the Inter-State River Water Disputes Act, 1956
Article 262 of the Constitution deals with disputes between states over the water of rivers that flow through more than one state. It lets Parliament make a law to settle such disputes, and also lets Parliament keep such disputes out of the ordinary jurisdiction of the Supreme Court and other courts. Parliament used this power to pass the Inter-State River Water Disputes Act, 1956, which sets up special tribunals to decide water shares.
The Supreme Court is hearing Tamil Nadu's plea because the case is about enforcing the Court's own 2018 judgment, not about deciding fresh shares. That is why the Court has asked Karnataka to follow the CWMA, the body set up under Section 6A of the 1956 Act.
- Tamil Nadu's claimed backlog: about 21 TMC (12 August 2026), about 15 TMC (7 October 2026)
- Water received by Tamil Nadu by 7 October 2026: about 46 TMC
- CWMA direction of 8 October 2026: 3,000 cusecs at Biligundlu for 15 days from 9 October
- Supreme Court heard the matter on 12 October 2026 and reserved its order
- Normal-year release by Karnataka at Biligundlu: 177.25 TMC (2018 judgment)
- Shares (2018): TN 404.25 TMC, Karnataka 284.75 TMC, Kerala 30 TMC, Puducherry 7 TMC
- CWMA and CWRC set up: 1 June 2018 (Section 6A, ISRWD Act, 1956)
- 1 TMC = one thousand million cubic feet of water; 1 cusec = one cubic foot of water flowing every second