The Mekedatu Balancing Reservoir and Drinking Water Project was originally proposed in the early 1980s. Karnataka envisioned constructing a balancing reservoir across the Cauvery River at Mekedatu, in what is now Ramanagara district, to regulate river flows, improve water management, provide drinking water to Bengaluru and surrounding areas, and generate hydropower. The dispute over the project is rooted in the broader Cauvery water-sharing conflict between Karnataka and Tamil Nadu. 

In 2007, the Cauvery Water Disputes Tribunal (CWDT) issued its final award allocating the basin's waters among the riparian states. The CWDT is a legal body set up by the Government of India on 2 June 1990. It was created under the Inter-State River Water Disputes Act, 1956, to solve the long-running water-sharing disagreement over the Cauvery River among Tamil Nadu, Karnataka, Kerala, and Puducherry. The award subsequently became the framework within which new projects involving the Cauvery had to be considered.

In February 2018, the Supreme Court modified the Tribunal's allocation and awarded Karnataka an additional 14.75 TMC of Cauvery water. The court also directed the establishment of the Cauvery Water Management Authority (CWMA) and the Cauvery Water Regulation Committee (CWRC). It reaffirmed that future projects would have to comply with the legal and regulatory framework governing the Cauvery waters. In October 2018, the Central Water Commission (CWC) granted Karnataka in-principle approval to prepare a Detailed Project Report (DPR) for the Mekedatu project.

Tamil Nadu challenged this decision before the Supreme Court. The court allowed Karnataka to proceed with preparation of the DPR but made clear that preparation of the report did not amount to permission to construct the project. Construction would require all necessary statutory approvals, including the concurrence of the Cauvery Water Management Authority. Karnataka submitted the Mekedatu DPR to the CWC in January 2019. The DPR proposed a reservoir with a gross storage capacity of 67.16 TMC, along with associated infrastructure. PIB/CWC information on the Mekedatu DPR

The project envisages using 4.75 TMC of water annually for drinking-water supply to Bengaluru and surrounding areas and generating approximately 400 MW of hydropower. The DPR subsequently remained under appraisal, with Karnataka seeking the clearances required to move the project forward. Environmental groups raised serious concerns about the project's impact on the Cauvery Wildlife Sanctuary, forest ecosystems and biodiversity. The proposed reservoir and associated works would involve substantial land use and the submergence of forest areas.

While the DPR process continued, the project became an increasingly prominent political issue in both states. In Tamil Nadu, political parties, farmer organisations and Cauvery-rights groups consistently opposed the project. They argued that storing water at Mekedatu could affect the quantity and timing of water reaching Tamil Nadu, particularly the Cauvery delta. Protests included demonstrations, petitions, memoranda, hunger strikes and rail blockades. In April 2015, around 190 protesters were arrested during demonstrations against Karnataka's dam proposal. In Karnataka, political parties across the political spectrum, farmer organisations, pro-Kannada groups and civil society organisations increasingly portrayed Mekedatu as important for Bengaluru's long-term drinking-water security. The Karnataka Legislative Assembly unanimously passed a resolution urging the Union Government to expedite the necessary clearances for the Mekedatu project.

The Karnataka Pradesh Congress Committee (KPCC) organised the “Namma Neeru, Namma Hakku Mekedatu Padayatra", presenting the project as a matter of Karnataka's right to use its Cauvery waters and as a solution to Bengaluru's drinking-water needs. The campaign became one of the most prominent mass mobilisations in support of the project. The Karnataka Police registered 17 FIRs against Congress leaders and workers in connection with alleged violations of COVID-19 restrictions during the mobilisation. Out of these, seven cases were disposed of by the court, including three which were quashed by the High Court. 

The project's land requirements became a major component of the environmental and social debate. The project is estimated to require about 5,252 hectares of land, with an estimated cost of around Rs 9,000 crore. Of the total land requirement, approximately 4,996 hectares would be submerged. The project is also expected to directly affect five villages, Sangama, Muthathi, Madivala, Koggedoddi and Bommasandra, with about 160.81 hectares of private land expected to be submerged and 233 families facing displacement. 

Tamil Nadu continued to challenge the project through the courts. In November 2025, the Supreme Court dismissed Tamil Nadu's petition against the Mekedatu project as premature, since the project had not yet obtained the statutory approvals required for construction. The ruling did not permit Karnataka to construct the project; the requirement for the necessary statutory clearances remained. During the same period, opposition continued on the ground in Tamil Nadu. In November 2025, members of the Cauvery Rights Retrieval Committee were arrested after burning copies of the Supreme Court's order during protests against Mekedatu. In December 2025, farmers and other protesters opposed to the Mekedatu project staged a rail blockade at Thanjavur Junction. Around ten protesters were arrested following the demonstration.

In May 2026, the Supreme Court rejected Tamil Nadu's review petition concerning the Mekedatu project, leaving the earlier dismissal of its challenge in place. The project, however, still required the statutory approvals necessary before construction could begin. In June 2026, the Tamil Nadu Legislative Assembly unanimously adopted a resolution urging the Union Government to withhold all statutory approvals for the Mekedatu project. Tamil Nadu farmer organisations also opposed proposals for a fresh tribunal on the Mekedatu issue and continued protests across the Cauvery delta. 

As of July 2026, the Mekedatu dispute remained unresolved. Karnataka continues to pursue the project through political advocacy and public mobilisation, arguing that the reservoir is important for Bengaluru's drinking-water security and water management.