Evaluation of simulation and optimisation models for WRP with PIs

Reservoirs play a vital role in the supply of water, especially in drought periods. By optimally operating reservoirs, target objectives can be achieved to acceptable levels. However, the optimal operation of large-scale water resource systems through the use of optimisation models is complicated, time-consuming and sometimes inapplicable, and thus the use of other methods that yield satisfactory near-optimal results with acceptable precision seems to be an attractive solution for this type of problem. This paper compares the performance of ModSim and Weap simulation models with that of Lingo optimisation packages for both single-reservoir and multi-reservoir systems in a period of low flow. For a better evaluation of the models' performance, criteria are developed and applied to the reservoir systems considered in this study. The results show that by considering volume reliability as an operation goal, optimisation models can be replaced by simulation models in single-reservoir systems. However, for such systems, simulation models improve the shortage index about 38% but the temporal reliability, resilience and vulnerability of the system yielded by simulation models are about half the values obtained by optimisation models. Moreover, volume reliability and resilience of the simulation and optimisation models in a multi-reservoir system show a difference of about 25% and 40% respectively. The difference is more than 300% when using other performance indices.