Droughts caused by precipitation deficits and increasing water consumption are intensifying worldwide, with negative economic and environmental consequences. The negative impacts can be mitigated by using optimized reservoir operation patterns and implementing rationing rules during droughts. These approaches involve meeting only a portion of total demand, allowing for water storage and accepting a small current deficit to mitigate severe future shortages. This research presents a case study to determine the operational command curves for Jareh Dam and to investigate the impact of reservoir operation under two management policies, Standard Operating Procedure (SOP) and rationing, on downstream drought indices, an aspect not previously studied. To achieve this, an optimization model coupled with a genetic algorithm was linked to a simulation model to determine the optimal values of command curves and rationing coefficients based on historical inflow data to the reservoir. The performance of the model was evaluated in the Allah River water resources system. In addition, the drought severity index (SDI), SOP performance, and rationing model performance during the base period were evaluated by calculating the objective function value or modified shortage index (MSI) and the resilience, vulnerability, and reversibility indices. The results showed that under the rationing model during the study period, the MSI value improved by 41% compared to the SOP method. In addition, the implementation of the rationing policy significantly improved the vulnerability of the system compared to the SOP method, reducing it from 64% to 26%.
