developing optimal operating reservoir rule-curves in drought periods

In this study, a simulation-optimization model is developed for deriving operational rule-curves in drought periods. to each reservoir, two rule-curves with adjustable monthly levels are introduced dividing the reservoir capacity into three zones between the normal water level and minimum operation level. to each zone of the reservoir and for each month of the year a hedging coefficient is introduced that determines the release from the reservoir. accordingly, an optimization problem is developed in which the objective is the minimization of water demands deficits in drought and the decision variables are the rule-curves levels and hedging coefficients. for optimization, a genetic algorithm equipped with a self-adaptive constraint handling strategy is used. to evaluate the objective function and constraints violations, the flexible and widely-used weap (water evaluation and planning) simulation model is exploited and coupled with the optimization solver. the model is then applied to the zohreh three-reservoir system in the southwest of iran and compared to the standard operation policy (sop). according to the sustainability indices for the system operated in drought, the obtained operating rule-curves are found significantly superior to the sop. as a result of applying the rule-curves, the modified shortage index (msi) and vulnerability (extent) of the system are respectively improved by 22% and 28% compared to the sop. consequently, the developed policy application resulted in longer periods of deficit (but less severe) as shown by decrease in reliability (5%) and resilience (40%) indices.