Climate variability is increasingly complicating fixed-quantum water-sharing formulas between states. Discuss with reference to the Cauvery basin.

Fixed-quantum sharing awards assume a stable "normal year" hydrology. In the Cauvery basin, erratic monsoons are turning such arithmetic allocations into annually renegotiated political flashpoints, exposing the limits of volume-based water federalism.

The fixed-quantum architecture in the Cauvery

• The CWDT award (2007), as modified by the Supreme Court in February 2018 (Karnataka's share raised by 14.75 TMC, Tamil Nadu's reduced correspondingly), fixes annual quanta to be delivered at the inter-state point [2].
• The Cauvery Water Management Scheme, 1 June 2018 created the CWMA and CWRC, which monitor daily storage across eight basin reservoirs and convert annual quanta into ten-daily/fortnightly releases measured at Biligundlu [1][3].
• Distress years are handled by pro-rata sharing, but without a codified rainfall-triggered trigger — so every deficient year reopens the arithmetic.

How climate variability disrupts it

• Delayed onset and longer dry spells mean inflows collapse even as calendar-bound release obligations continue: Karnataka opposed the September 2026 CWMA order of 6,000 cusecs/day for 15 days (~7.8 tmc ft), citing "critically inadequate" storage in its four basin reservoirs [6].
• Volatile quanta reveal ad-hocism — a July 2026 direction of 3,500 cusecs rose to 6,000 within weeks [6].
• Rainfall deficits simultaneously hit upstream drinking water (Bengaluru) and downstream kuruvai/samba cycles in the delta; the Economic Survey repeatedly flags rainfall variability and urges micro-irrigation ("Per Drop More Crop") [4].
• Result: politicisation, repeated Supreme Court petitions despite Article 262, and eroded compliance with technical bodies.

Climate stress has shifted the problem from dividing a known quantity to sharing an uncertain one. The way forward lies in share-of-actual-flow formulas with real-time telemetry, an explicit distress-sharing protocol, basin-level crop diversification and demand management, and institutional strengthening through the proposed single standing tribunal with a Disputes Resolution Committee [5]. Treating the river as a shared basin resource, not a state entitlement, is the cooperative-federal spirit the Constitution envisages.