Tamil Nadu Chief Minister C. Joseph Vijay has written to Prime Minister Narendra Modi, urging the Union government to withhold all statutory and administrative approvals for Karnataka's proposed Mekedatu Dam project. In his letter dated 28 July, the Chief Minister contended that clearing the project would directly violate the Cauvery Water Disputes Tribunal (CWDT) Award and the Supreme Court's 2018 judgment on the Cauvery water-sharing dispute.

What Prompted the Letter

The trigger was a reply given by the Union Minister of State for Jal Shakti in the Rajya Sabha, which stated that the Supreme Court's 16 February 2018 judgment did not expressly require Karnataka to obtain the consent of lower riparian states before constructing any structure across the Cauvery River. Chief Minister Vijay described this response as 'legally unsustainable' and argued it overlooked settled judicial principles governing inter-state river disputes.

The Legal Argument

Vijay invoked the Supreme Court's Constitution Bench judgment in the Alamatti Dam case between Karnataka and Andhra Pradesh, in which the court held that the consent of downstream riparian states was essential before an upstream state could undertake such projects. He argued this principle applies squarely to the Mekedatu proposal and cannot be sidestepped.

The letter further noted that the Supreme Court, while upholding the CWDT Award in 2018, affirmed that states could regulate water within their territories only in a manner consistent with the Tribunal's directions. Vijay also cited the Tribunal's earlier insistence on coordinated water releases for Kerala's Pambar Hydro-electric Project as precedent for protecting downstream interests.

What Tamil Nadu Has Demanded

Chief Minister Vijay made three specific requests to the Prime Minister. First, that the Centre withdraw the Rajya Sabha reply. Second, that no approval be granted to the Mekedatu project unless it fully complies with the CWDT Award and the Supreme Court judgment. Third, that any future consideration of the project be preceded by a comprehensive legal and technical examination involving all affected states.

The letter also invoked provisions of the Tribunal Award that require mutual agreement and consultation before any action affecting scheduled water deliveries can be taken — a procedural safeguard Vijay argued Karnataka has not fulfilled.

Why the Cauvery Dispute Remains Sensitive

The Cauvery River is the primary water source for millions of farmers and residents across Tamil Nadu, Karnataka, Kerala, and Puducherry. The Mekedatu project, proposed by Karnataka as a balancing reservoir near Bengaluru, has long drawn opposition from Tamil Nadu, which fears it would allow Karnataka to regulate flows and reduce downstream water availability. This is not the first time Tamil Nadu has formally objected — successive state governments have raised the issue at the Centre and before the Supreme Court over several years.

With the Union government's Rajya Sabha reply now interpreted by Chennai as a shift in the Centre's legal reading, the dispute has entered a politically charged new phase ahead of the next Cauvery review cycle.