Mekedatu Balancing Reservoir-cum-Drinking Water Project

The Mekedatu project is a large dam and reservoir that Karnataka wants to build on the Cauvery river at Mekedatu, near Kanakapura in Karnataka, close to the border with Tamil Nadu. Karnataka calls it a "balancing reservoir-cum-drinking water project": it says the dam will store water to supply drinking water to Bengaluru, generate about 400 MW of electricity, and help it release water to Tamil Nadu in a steady way.

Tamil Nadu, the downstream state, strongly opposes it because it fears the dam will reduce or control the water that reaches its farmers.

Where exactly is it?

Mekedatu is a deep, narrow gorge on the Cauvery at its confluence with the Arkavathi river, in Kanakapura taluk. The name means "goat's leap" in Kannada. Local legend says the gorge is so narrow that a goat once jumped across it to escape a tiger. The site is only a short distance upstream of Biligundlu, the gauging point on the inter-state border where the water Karnataka releases to Tamil Nadu is measured. The reservoir area lies largely inside the Cauvery Wildlife Sanctuary.

Why does Karnataka want it?

Karnataka gives three main reasons:

• Drinking water for Bengaluru: Bengaluru is one of India's fastest-growing cities and already depends heavily on Cauvery water. India's National Water Policy (2012) gives drinking water the first priority. The Supreme Court's 2018 judgment gave Karnataka an extra 4.75 TMC of Cauvery water for Bengaluru's drinking water needs.
• Balancing releases: Karnataka says the reservoir would store extra water in good monsoon years, water that would otherwise flow down unused, and help it meet Tamil Nadu's share in bad years.
• Power: A hydropower station of about 400 MW.

A simple way to picture "balancing": think of a water tank between a well and a house. When the well gives a lot of water, the tank fills. When the well runs low, the tank keeps supply going. Karnataka says Mekedatu would work like that tank for the Cauvery.

Why does Tamil Nadu object?

• Control over flows: A large reservoir just above the border would give Karnataka the physical ability to hold back water. Tamil Nadu fears the monthly pattern of releases, which matters for its crop seasons, could be disturbed.
• The award and the judgment: Tamil Nadu argues that a new storage project on an inter-state river needs the consent of the downstream states, and that the project goes against the 2007 Tribunal award and the 2018 Supreme Court judgment.
• Deficit basin: The Cauvery Water Disputes Tribunal treated the Cauvery as a deficit basin (there is less water than all the states' needs). Tamil Nadu says any new storage in such a basin can only hurt the lower state.
• Delta farming: The Cauvery delta (Thanjavur, Tiruvarur, Nagapattinam areas) is called the "rice bowl" of Tamil Nadu, and the farmers there depend on timely water for the kuruvai and samba paddy seasons.

How has the project developed?

1. Karnataka has proposed a dam at Mekedatu for decades. The present design is a single large reservoir of roughly 66 to 67 TMC.
2. On 22 November 2018, the Central Water Commission (CWC) allowed Karnataka to prepare a Detailed Project Report (DPR). Tamil Nadu challenged this in the Supreme Court within days.
3. Karnataka submitted the DPR to the CWC in January 2019, at an estimated cost of about ₹9,000 crore. Copies were sent to the Cauvery Water Management Authority (CWMA).
4. On 13 November 2025, a Supreme Court Bench led by the then Chief Justice B.R. Gavai dismissed Tamil Nadu's applications as premature. The Court said Tamil Nadu could act if the CWC actually approves the DPR. It also said that before any decision, the views of Tamil Nadu, the CWMA and the Cauvery Water Regulation Committee (CWRC) must be taken, and that Karnataka remains bound to release Tamil Nadu's share regardless of the project.
5. The CWC returned the 2019 DPR to Karnataka for revision, as the Union government told Parliament in July 2026.
6. Karnataka resubmitted the DPR with a compliance report on 13 August 2026. The latest cost estimate is about ₹16,745 crore.

What approvals does such a project need?

A large inter-state river project goes through many gates:

• Techno-economic appraisal by the CWC (checks engineering, water availability, inter-state aspects) and acceptance by the Ministry of Jal Shakti's Advisory Committee on irrigation, flood control and multipurpose projects.
• Consideration by the CWMA, since the Supreme Court's 2018 scheme gives it the role of implementing the Cauvery water-sharing order.
• Environmental clearance under the EIA Notification, 2006.
• Forest clearance under the Forest (Conservation) Act, 1980 (renamed in 2023 as the Van (Sanrakshan Evam Samvardhan) Adhiniyam, 1980), because forest land will be submerged.
• Wildlife clearance from the Standing Committee of the National Board for Wildlife (NBWL), because the project is inside a wildlife sanctuary.

Environmental cost

The project would need about 5,000 hectares of forest land. Reports on the proposal sent to the Environment Ministry put it at about 5,096 hectares, of which about 4,777 hectares lie in the Cauvery Wildlife Sanctuary. Karnataka's revised DPR, as reported in August 2026, puts the submerged forest land at about 12,500 acres (about 5,060 hectares) and the trees to be felled at about 8.90 lakh.

The area is part of an elephant movement corridor. The Cauvery here is also a habitat of the hump-backed mahseer, a large fish listed as Critically Endangered on the IUCN Red List. A few villages (such as Sangama, Muthathi, Madivala, Koggedoddi and Bommasandra) and some private land would also be affected.

Commonly confused concepts

• Mekedatu vs Hogenakkal: Both are on the Cauvery near the border. Mekedatu is in Karnataka, where Karnataka proposes a dam. Hogenakkal is a waterfall on the Tamil Nadu side, known for the Hogenakkal drinking water project of Tamil Nadu.
• Mekedatu vs Biligundlu: Mekedatu is the proposed dam site. Biligundlu is the measuring point on the border where Karnataka's releases to Tamil Nadu are counted.
• Balancing reservoir vs Storage dam vs Run-of-the-river project: A balancing reservoir smooths out releases over time. A storage dam holds large volumes for later use, such as irrigation. A run-of-the-river project uses the river's flow for power with little storage. Mekedatu's size (about 67 TMC) makes it a very large storage structure even though it is called a balancing reservoir.
• DPR approval vs Construction approval: Permission to prepare a DPR is not approval of the project. A DPR must still pass appraisal and all clearances.

Issues, criticism and the way forward

• Trust between states: The basic problem is lack of trust. Tamil Nadu fears that physical control over water upstream will matter more than legal promises during a drought.
• Role of the CWMA: Experts suggest that if the dam is ever built, its operation could be placed under the CWMA's control, so releases follow the Supreme Court's monthly schedule. This could reduce Tamil Nadu's fears.
• Ecology vs drinking water: Submerging about 5,000 hectares of a wildlife sanctuary has a high ecological cost. Critics argue Bengaluru's needs could also be met by fixing leaky pipes, recycling wastewater and recharging lakes.
• Distress sharing: The Cauvery dispute keeps returning because there is no agreed formula for sharing water in bad monsoon years. A clear distress-sharing formula would reduce such conflicts.
• Way forward: Transparent data sharing, decisions through the CWMA rather than unilateral steps, completion of the full appraisal with views of all co-basin states, as directed by the Supreme Court, and serious study of alternatives.

Concepts to Know

• TMC (thousand million cubic feet): A unit of water volume used in Indian river disputes. One TMC is about 28.3 billion litres.
• Upper and lower riparian: On a river, the upper riparian state is upstream (Karnataka for the Cauvery) and the lower riparian state is downstream (Tamil Nadu).
• Co-basin states: All states that share a river's basin. For the Cauvery: Karnataka, Tamil Nadu, Kerala and the Union Territory of Puducherry.
• Detailed Project Report (DPR): A full technical and financial plan of a project, covering design, cost, water use, environmental impact and benefits.
• Central Water Commission (CWC): India's top technical body on water resources, under the Ministry of Jal Shakti. It examines major water projects.
• Deficit basin: A river basin where the water available is less than the total demand of all the states that share it.
• Critically Endangered: The IUCN Red List category just before "Extinct in the Wild", for species at extremely high risk of extinction.