Mekedatu Dam Controversy : CM Vijay’s Letter to PM Modi, Karnataka’s 67.16 TMC Project, Cauvery Water Dispute History and Tamil Nadu’s Legal Battle Explained

The Mekedatu Dam controversy has flared up again. On 7 November 2026, Tamil Nadu Chief Minister C. Joseph Vijay wrote to Prime Minister Narendra Modi objecting to a reported site inspection by Union government officials at the proposed Mekedatu dam site in Karnataka. He urged the Centre not to grant any statutory or administrative approval to the project without the consent of the Cauvery co-basin states, and said Cauvery delta farmers were living in “perpetual anxiety”.

What is the Mekedatu project? Why does Tamil Nadu oppose it so strongly? What does the Cauvery water dispute history say, and what legal steps has Tamil Nadu taken? This Election Guru explainer covers the full Mekedatu story.

Mekedatu Dam at a Glance

Detail	Information
Project	Mekedatu balancing reservoir and drinking water project
State proposing	Karnataka
River	Cauvery, just upstream of the Karnataka – Tamil Nadu border
Storage	67.16 TMC (thousand million cubic feet)
Purpose	Drinking water for Bengaluru and hydroelectric power
Opposed by	Tamil Nadu (lower riparian state)
Latest flashpoint	Tamil Nadu CM’s letter to PM Modi, 7 November 2026

What Is the Mekedatu Project?

Mekedatu – literally “goat’s leap” in Kannada – is a narrow gorge on the Cauvery river close to the inter-state border. Karnataka plans to build a large balancing reservoir there with a storage capacity of 67.16 TMC. Karnataka says the project is mainly meant to meet Bengaluru’s drinking water needs and to generate hydroelectric power, and that it will help regulate water releases to Tamil Nadu in lean years.

Why Tamil Nadu Opposes Mekedatu

Tamil Nadu, the lower riparian state, fears that a large reservoir just above the border would give Karnataka control over water that would otherwise flow freely into Tamil Nadu, particularly during the monsoon. Chief Minister Vijay argues that the reservoir could block flows to Tamil Nadu and affect the monthly releases stipulated by the Supreme Court. The Cauvery delta in Tamil Nadu – the state’s rice bowl – depends heavily on these flows.

What CM Vijay Wrote to PM Modi

• No statutory or administrative clearance for Mekedatu without the consent of all co-basin states.
• The Jal Shakti and Environment ministries should stop site inspections, technical evaluations and clearances without the consent of lower riparian states.
• Any action arising from the reported central site inspection should be deferred.
• Karnataka should be advised not to proceed without the agreement of co-basin states.
• Considering the DPR and holding unilateral central inspections at this stage is “highly inappropriate”.

Vijay also pointed out that 2026-27 is a deficit water year and that Karnataka had not released Tamil Nadu’s due share of water, even on a pro-rata basis. He referred to reported meetings between Karnataka’s Chief Minister and Union ministry officials seeking clearance for the project’s Detailed Project Report (DPR) without Tamil Nadu’s concurrence.

Tamil Nadu’s Legal and Political Steps in 2026

Date	Step
27 May 2026	Application before the National Green Tribunal seeking to restrain environmental permissions until inter-state issues are settled
19 June 2026	Tamil Nadu Assembly unanimously passed a resolution opposing any clearance to Karnataka
28 July 2026	CM Vijay’s earlier letter to PM Modi
3 August 2026	Writ petition in the Supreme Court challenging the Jal Shakti Ministry’s December 2025 DPR guidelines for Cauvery basin projects (pending)
7 November 2026	Letter to PM Modi objecting to site inspection

Cauvery Water Dispute: A Short History

The Cauvery dispute between Karnataka and Tamil Nadu goes back to agreements of 1892 and 1924 between the Madras Presidency and the princely state of Mysore. After decades of conflict, the Centre set up the Cauvery Water Disputes Tribunal (CWDT) in 1990.

Year	Milestone
1892 & 1924	Agreements between Madras Presidency and Mysore
1990	Cauvery Water Disputes Tribunal set up
2007	Tribunal’s final award
16 Feb 2018	Supreme Court judgment modifies the award
2018	Cauvery Water Management Authority (CWMA) and Regulation Committee set up

The 2018 Supreme Court Verdict

In its 16 February 2018 judgment, the Supreme Court modified the tribunal’s award. Karnataka’s share was increased to 284.75 TMC and Tamil Nadu’s share was fixed at 404.25 TMC, with Kerala getting 30 TMC and Puducherry 7 TMC. The court allowed extra water for Bengaluru’s drinking needs and directed Karnataka to release 177.25 TMC annually at Biligundlu on the inter-state border, in monthly instalments. Tamil Nadu argues that any new project must be consistent with this judgment and the tribunal’s final award.

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Karnataka’s Argument

Karnataka says Mekedatu lies entirely within its territory, that drinking water for a fast-growing Bengaluru is a priority under the Supreme Court verdict, and that the reservoir will not reduce Tamil Nadu’s share – instead, it will help store surplus water and ensure regulated releases. Successive Karnataka governments across parties have backed the project.

Why Mekedatu Is Also a Political Issue

Mekedatu is an emotive issue in both states. In Tamil Nadu, every major party opposes it, and the Assembly’s June 2026 resolution was unanimous. For Vijay, whose government took office in 2026, standing firm on Cauvery is crucial to win the trust of delta farmers. In Karnataka, the project is a promise to Bengaluru and the old Mysore region. The Centre, caught between the two, has to balance federal relations and legal obligations.

What Happens Next

• The Supreme Court’s decision on Tamil Nadu’s writ against the DPR guidelines.
• NGT proceedings on environmental clearances.
• The Centre’s response to Vijay’s letter and Karnataka’s push for DPR clearance.
• Monthly water releases to Tamil Nadu in the deficit year 2026-27.

The Cauvery River: Key Facts

The Cauvery (Kaveri) rises at Talakaveri in Kodagu district of Karnataka and flows about 800 km through Karnataka and Tamil Nadu before reaching the Bay of Bengal. Its basin also covers parts of Kerala and Puducherry. Major reservoirs include the Krishna Raja Sagar (KRS) and Kabini in Karnataka and the Mettur dam (Stanley Reservoir) in Tamil Nadu. The river enters Tamil Nadu near Hogenakkal, close to the Mekedatu site, and feeds the fertile Cauvery delta in Thanjavur, Tiruvarur and Nagapattinam districts.

State / UT	Share Under 2018 SC Verdict
Tamil Nadu	404.25 TMC
Karnataka	284.75 TMC
Kerala	30 TMC
Puducherry	7 TMC

Why Bengaluru Needs More Water

Bengaluru is one of India’s fastest-growing cities, and its water supply depends heavily on the Cauvery, pumped over long distances and a steep elevation. The city faced a severe water crisis in 2024 when many borewells dried up. Karnataka argues that the Supreme Court recognised Bengaluru’s drinking water needs in 2018 and that Mekedatu is essential for the city’s future.

Distress Years: The Real Flashpoint

In normal or surplus years, Cauvery water sharing works without much trouble. Conflicts flare in deficit years, when rainfall in Karnataka’s catchment is poor and both states need water at the same time. In such years, the Cauvery Water Management Authority applies a pro-rata “distress sharing” formula. Tamil Nadu says Karnataka has not released its due share even on this basis in 2026-27, which is why it fears that a new reservoir would make its position even weaker.

Past Cauvery Crises

Year	What Happened
1991	Violence in Karnataka after the tribunal’s interim order
2007	Tribunal’s final award triggers protests
2016	Violence in Bengaluru after Supreme Court orders release of water to Tamil Nadu
2018	Supreme Court’s final verdict and creation of CWMA
2023	Fresh protests in both states during a deficit year

How Inter-State River Disputes Are Settled in India

Article 262 of the Constitution allows Parliament to make laws for settling inter-state river water disputes. Under the Inter-State River Water Disputes Act, 1956, the Centre sets up a tribunal whose award becomes binding. In the Cauvery case, the Supreme Court heard appeals against the tribunal’s award and gave the final verdict in 2018. Any new project on an inter-state river usually needs clearance from the Central Water Commission, environmental clearance and, in practice, the agreement of the other basin states.

Mekedatu: Arguments at a Glance

Karnataka Says	Tamil Nadu Says
Project is within Karnataka’s territory	Cauvery is an inter-state river; consent of co-basin states is needed
Needed for Bengaluru’s drinking water	Bengaluru’s share is already provided in the 2018 verdict
Will help regulate releases to Tamil Nadu	Will give Karnataka control over free flows in good years
Will generate clean hydropower	Will submerge forest areas and affect wildlife

Environmental Concerns

The proposed reservoir area lies in a forested landscape near the Cauvery Wildlife Sanctuary, home to elephants and other wildlife. Environmental clearance would require a detailed assessment of forest loss and wildlife impact, which is why Tamil Nadu has approached the National Green Tribunal to prevent any clearances while inter-state issues remain unresolved.

What Is a TMC?

Water in river disputes is measured in TMC – thousand million cubic feet, or one billion cubic feet. One TMC is roughly 28.3 billion litres. So Mekedatu’s proposed storage of 67.16 TMC would hold about 1.9 trillion litres of water – a very large reservoir in the context of the Cauvery, where Tamil Nadu’s annual share is 404.25 TMC.

Hogenakkal: Tamil Nadu’s Own Drinking Water Project

Tamil Nadu has its own Hogenakkal Integrated Drinking Water Project near the same stretch of the Cauvery, which supplies drinking water to Dharmapuri and Krishnagiri districts. Karnataka had objected to it in 2008, leading to protests in both states. Karnataka now cites drinking water needs for Bengaluru in a similar way – showing how both states use the “drinking water” argument when it suits them.

Political Parties’ Stand in Tamil Nadu

Party	Stand on Mekedatu
TVK (ruling)	Strongly opposes; CM Vijay has written twice to PM Modi
DMK	Opposes; raised the issue repeatedly when in power
AIADMK	Opposes; has demanded Centre reject the DPR
BJP (Tamil Nadu unit)	Has opposed the project in Tamil Nadu
Farmers’ groups	Delta farmers’ associations oppose any new dam upstream

Mekedatu is one of the few issues on which almost all of Tamil Nadu’s parties agree, as seen in the unanimous Assembly resolution of June 2026.

What the Centre Can Do

• Ask Karnataka and Tamil Nadu to discuss the project under the CWMA framework.
• Withhold clearance of the DPR until the basin states agree.
• Await the Supreme Court’s decision on Tamil Nadu’s challenge to the DPR guidelines.
• Use the Central Water Commission’s technical review to assess downstream impact.

Cauvery Delta: Why Farmers Are Anxious

The Cauvery delta in Tamil Nadu – spread across Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai and parts of nearby districts – grows the bulk of the state’s paddy in the kuruvai and samba seasons. The opening of the Mettur dam on 12 June each year is a key date for delta farmers. In deficit years, delayed or reduced releases from Karnataka can mean failed crops, which is why any project upstream triggers strong reactions.

Mekedatu Dam Controversy FAQ