Karnataka seeks to contest Cauvery water allocation, cites changing hydrological conditions

Karnataka has signalled to the Supreme Court that it may seek to reopen the Cauvery water-sharing allocation, citing “inequitable allocation” and “changed circumstances” caused by changing hydrological conditions.

According to a report by The Hindu, the state made the submission on October 7, in its response to Tamil Nadu’s application over the backlog in Cauvery water releases. Karnataka said it reserved the right to seek a reconsideration of the allocation made by the Cauvery Water Disputes Tribunal and modified by the Supreme Court in 2018.

Karnataka’s 40-page response, filed by advocate Nishanth Patil and settled by senior advocate Mohan Katarki, referred to the legal principle of rebus sic stantibus, under which arrangements can be revisited when circumstances underlying them have substantially changed.

“In view of the looming inequity, the state of Karnataka reserves its right to apply in the changed circumstances for reopening of the inequitable allocation in the Award of Tribunal read with judgment of the Supreme Court. The normal practice is that the water allocations are periodically revisited,” the response said.

The report said Karnataka also cited the Union government’s position on the Indus Waters Treaty of 1960, which India has sought to modify on the ground of changed circumstances, as an example of water-sharing arrangements being revisited.

Under the Cauvery Tribunal’s award, as modified by the Supreme Court in 2018, the basin’s annual flow was assessed at 740 tmc ft at 50% dependability at the Lower Coleroon Anicut. Karnataka was allocated 284.75 tmc ft, Tamil Nadu 404.25 tmc ft, Kerala 30 tmc ft and Puducherry 7 tmc ft. Another 10 tmc ft was earmarked for environmental flows and 4 tmc ft as inevitable wastage to the sea.

The framework provides for proportionate sharing of distress when the annual yield falls below 740 tmc ft because of deficient rainfall. Karnataka, however, argued that there is no scientific formula for determining how distress should be shared between the states, the report added.

The state said the 2026-27 water year had become a distress year following the failure of the southwest monsoon between June and September. It argued that the allocation fixed by the Tribunal and affirmed by the Supreme Court did not account for subsequent changes in hydrology caused by climate change, environmental degradation and shifting monsoon patterns.

Karnataka also pointed to the absence of a monthly component in the annual 740 tmc ft allocation. It said this was significant because the Cauvery basin receives rainfall during two distinct seasons, with the southwest monsoon between June and September and the northeast monsoon from October to December or later.

According to the state, the northeast monsoon mainly benefits downstream Tamil Nadu, while a failure of the southwest monsoon leaves Karnataka facing acute water stress. It argued that this seasonal difference should be considered when determining water-sharing during distress years.

Karnataka further questioned the basis for Tamil Nadu receiving 404.25 tmc ft, saying the allocation gave weight to the state’s claim of historic irrigation. It said Karnataka had been allocated 284.75 tmc ft out of the 483 tmc ft available up to Biligundlu, despite large parts of the state being drought-prone.

The state argued that drinking water should receive the highest priority during a distress year, followed by irrigation in drought-prone areas.

“In a distress water year, the first priority should be given to drinking water requirements, since people cannot live without drinking water. The second priority must be given to the dry irrigation in the drought areas, since irrigation in these drought areas provides minimum income and sustenance to the farmers,” the response said.

Karnataka said its four Cauvery basin reservoirs currently held 48.878 tmc ft of water, of which 35 tmc ft would be required for drinking. That would leave 13.878 tmc ft for dry irrigation, which the state said was wholly inadequate for the command areas served by the four reservoirs.

The submission comes amid continuing proceedings between Karnataka and Tamil Nadu over Cauvery releases. In September, the Supreme Court declined to entertain a separate petition seeking, among other things, the reallocation of 70 tmc ft from Tamil Nadu’s share to Karnataka, noting that the two states were already contesting the dispute before it.