Evaluation of performance indices of reservoir system management models in drought events

Reservoirs are one of the most important infrastructures that play a vital role to supply water in specially drought events. By optimum operation of reservoirs the target objectives can be obtained in an acceptable level. But, hence the optimum operation of the large water resources systems by using the optimization models is complicated, time consuming and sometimes inaccessible, the use of other methods which yields the satisfactory near-optimum results with acceptable precession seems to be an acceptable solution for this type of problems. In this study the performance of MODSIM and WEAP simulation models have been compared to those obtained by Lingo optimization packages for a single-reservoir systems as well as in a multireservoir system in a period of low flow condition. For better evaluation of model's performances, some criteria have been developed and applied for the reservoir systems in this study. The results showed that by considering the volume reliability as the operation goal, the simulation models can be replaced by the optimization models in single-reservoir systems.However, in such systems the simulation models increases the relational deficit for about %38, whereas the temporal reliability, resiliency and vulnerability of the system yielded by simulation models is about half of those obtained by the optimization models. Moreover, the volume reliability and resiliency of the system are not the same in simulation and optimization models. The discrepancy of the volume reliability in optimization and simulation models is about 25% and the discrepancy of resiliency in the mentioned models is 40%. The discrepancy of other performance indices is more than 300%.