The Mekedatu Balancing Reservoir cum Drinking Water Project is proposed on the Cauvery river in Karnataka. It has been the subject of a long-running dispute between Karnataka and Tamil Nadu. Karnataka says the project is needed to meet Bengaluru's future drinking water needs and improve management of the Cauvery basin. Tamil Nadu says it could alter downstream river flows and undermine the Cauvery water-sharing framework. The project has also raised environmental concerns because it is proposed inside the ecologically sensitive Cauvery Wildlife Sanctuary.
Timeline
1980s–1990s: Karnataka begins exploring possibility of a reservoir at Mekedatu
2003–2012: Preliminary studies and concept reports prepared
2013: Work started with preparation of preliminary report
2014: Karnataka calls for tenders for inviting consultants for the project.
2015: Tender awarded to one consultant. Tamil Nadu objects, arguing consent of lower riparian states must.
2016: Detailed Project Report (DPR) for ₹5,900crore prepared by Karnataka. Tamil Nadu files objections before Supreme Court
2017: Karnataka gives in-principle approval for DPR and submits it to CWC in Bengaluru. They raise objections and list corrections.
2018: Objections complied with. Also, SC judgment on Cauvery water-sharing dispute, modifies water allocations, affirms need for regulation; Centre sets up Cauvery Water Management Authority (CWMA)
2019: Karnataka submits DPR to CWC Delhi with a budget estimate of ₹9,000crore. Tamil Nadu reiterates opposition
2021: Karnataka includes Mekedatu in state budget and allocates funds
2022: Karnataka conducts public outreach, including the "Mekedatu Padayatra”; Tamil Nadu raises objections before CWMA and Centre
2023: Proposal sent for environment and forest clearances. Remains pending till date.
2024: CWMA deliberated on the DPR and referred it back to the CWC; no construction commenced
2025–2026: SC rejected Tamil Nadu's challenge to the preparation of the DPR in late 2025, but approvals from the CWC and other statutory authorities remain pending and no construction has begun. The DPR itself has since undergone revision.
2026: Karnataka revises DPR with inputs from CWC and CWMA, including current scheduled rates and additional water allocation.
What is the Mekedatu project?
The Mekedatu Balancing Reservoir cum Drinking Water Project is a proposed multipurpose reservoir across the Cauvery River at Mekedatu, or "Goat's Crossing", about 110 km from Bengaluru. A balancing reservoir stores water for later use and helps regulate water releases.
The Karnataka government says the project has three main aims: to supply drinking water to the Bengaluru Metropolitan Region and nearby towns, store surplus monsoon water that would otherwise flow downstream, and generate about 400 MW of hydroelectric power. It has a proposed live storage capacity of 59.46 Thousand Million Cubic feet (TMC).
What has Karnataka changed in the project?
The first Detailed Project Report (DPR), submitted in 2019, proposed using 4.75 TMC of water for drinking purposes.In April 2026, Karnataka revised the proposal. It increased the proposed consumptive use (amount of water used and not returned to the river) to 6.95 TMC and added 5% dead storage. The State said this was needed because Bengaluru's population has grown rapidly and its water demand has increased.The revised proposal also includes the Shivanasamudra Run-of-River Power Project and a diversion weir across the Cauvery River.
Why is the project back in the news?
The Central Water Commission (CWC) examined Karnataka's revised proposal and said the 2019 DPR could no longer be processed because the project had undergone substantial changes. The Commission asked Karnataka to prepare an entirely fresh DPR. It said the new report should include the revised water requirement, the Shivanasamudra Run-of-River Power Project, diversion structures and updated technical details. Karnataka's Cauvery Neeravari Nigam Limited is now preparing the revised DPR. The estimated cost of the project has also increased from around ₹9,000 crore in 2018-19 to nearly ₹16,000 crore.
What did the CWC say about Karnataka's calculations?
The Commission questioned how Karnataka calculated the reservoir's live storage requirement (amount of water in the reservoir that can actually be used). It said the calculations were based on outdated assumptions about Bengaluru's drinking water demand. It also said the proposal continued to use water utilisation figures from 1990. The CWC further observed that the proposed consumptive use of 6.95 TMC appeared to be higher than what was permissible under the Supreme Court's allocation.
Where is the project proposed?
The proposed reservoir is inside the Cauvery Wildlife Sanctuary. It is located where the Cauvery River passes through a narrow rocky gorge. The site is in Kanakapura taluk of Ramanagara district and Kollegal taluk of Chamarajanagara district. It is around 110 km from Bengaluru.
How much land will the project require?
The project requires nearly 12,000 acres of land. Around 98% of this is forest land. The remaining 2% is private land. Four villages near the sanctuary will be acquired. Around 500 households are expected to be affected. Karnataka says rehabilitation packages are being prepared. The State is also identifying alternative forest land to compensate for the forest area that will be diverted.
Why does Karnataka say the project is needed?
Karnataka says Bengaluru's population has grown rapidly and so, the city's drinking water demand has increased. The State also says the project will capture surplus monsoon runoff (rainwater that flows into the river during the monsoon) that would otherwise flow downstream unused. It says this water can then be stored for drinking purposes.
How does Karnataka say the project will help manage Cauvery waters?
Karnataka says the project will reduce pressure on existing reservoirs such as Krishnaraja Sagar (KRS), Kabini and Hemavathi. According to the State, better storage will help it regulate water releases while ensuring the annual delivery of 177.25 TMC to Tamil Nadu, as directed by the Supreme Court. The State also says the project would provide greater flexibility during distress years, when there is no clearly defined distress-sharing formula. Karnataka maintains that Mekedatu is not an irrigation project.
Why does Tamil Nadu oppose the project?
Tamil Nadu strongly disagrees with Karnataka's interpretation. It says the project violates both the Cauvery Water Disputes Tribunal (CWDT) award and the Supreme Court's 2018 judgment. It has therefore asked the CWC not to process the proposal.
What are Tamil Nadu's main concerns?
Tamil Nadu says the proposed reservoir is just upstream of the inter-State border. According to the State, this would allow Karnataka to store water flowing in from the uncontrolled intermediate catchment, or the area between Krishna Raja Sagara, Kabini and Biligundlu where rainwater naturally flows into the river without first passing through a reservoir.
Tamil Nadu says these natural flows were already taken into account while deciding water allocations under the Tribunal award. It says those allocations were later affirmed by the Supreme Court.The State also argues that the Tribunal did not provide for a new reservoir of this size. It says additional upstream storage could affect scheduled downstream releases. It also says Karnataka already has enough storage infrastructure to meet Bengaluru's drinking water needs.
What are the environmental concerns?
Environmentalists say the project could lead to one of the largest ecological losses in southern India. Around 5,100 hectares of forest are expected to be submerged. Much of this area is part of the Mysore Elephant Corridor, one of the most important wildlife movement routes in the region. The forests are home to tigers, leopards, Asian elephants, sloth bears and recently documented honey badgers. Cauvery in this region also supports the critically endangered hump-backed mahseer, one of India's most iconic freshwater fish species.
What ecological losses do experts warn about?
Experts say submerging these forests would lead to irreversible losses of ecosystem services.These include watershed protection, storing carbon, climate regulation and keeping forests connected so wildlife can move between them the Western Ghats and eastern forest landscapes.
Researchers from the Indian Institute of Science estimate that these forests provide ecosystem services worth more than ₹5,000 million every year. They also estimate the forest asset value at more than ₹125 billion as net present value.
Conservationists also say the project falls within core forest areas and eco-sensitive zones. They say it may go against court orders meant to protect officially identified elephant corridors.
What alternatives have experts suggested?
Some environmentalists and water experts say Bengaluru can improve its water security without building a large new reservoir.They suggest expanding rainwater harvesting across the city, improving groundwater recharge and making better use of treated wastewater. They estimate treated wastewater at around 16 TMC every year.
What other alternatives have been proposed?
Some experts also point out that Bengaluru already receives nearly 19 TMC of water every year. They say the Cauvery Stage VI drinking water project will soon add another 675 million litres per Day(MLD). Other suggestions include upgrading the existing 66-kV substation at Hegnur instead of building new power infrastructure near Mekedatu, or investing more in solar power generation and battery energy storage instead of the hydropower component.
What approvals are still needed?
The wildlife clearance from the National Board for Wildlife (NBWL) to undertake the feasibility study is awaited. Also needed are forest clearance, environmental clearance, approval from the CWC based on a revised DPR and compliance with the Cauvery water-sharing framework before construction can begin.