Optimal hedging policy for the long-term operation of Parambikulam-Aliyar multi-reservoir system

The coordinated operation of multi-purpose, multi-reservoir systems pose significant challenges owing to inflow uncertainties, competing stake-holder preferences, interstate agreement conditions and inter-basin transfer requirements. The Parambikulam-Aliyar Project (PAP) in southern India exemplifies such complexity, with five major reservoirs and a diversion weir jointly operated by two states under marked hydroclimatic variability and agreement-based water-transfer obligations. This study develops a hedging-based operating policy within a Parameterisation-Simulation-Optimization (P-S-O) framework, using compact rule representations and a multi-objective evolutionary algorithm to derive adaptive reservoir operation strategies. System performance is evaluated using 21 years of historical inflows and further assessed through 400-year long synthetic inflow sequence representing hydrologic variability. The proposed hedging policy maintains critical storage during dry spells, delivers smooth seasonal deficit patterns and supports drought-year resilience and achieves agreement-compliant transfers without compromising energy production. The long-term synthetic simulations confirm the robustness of the optimal policies derived.