The pattern of water use operation is important to ensure the continuity of water supply system of a reservoir. This pattern, which is usually called power rule curve in a hydropower system, should be optimally obtained, so that the yielded electrical power also becomes optimal while the continuity of reservoir storage can also be tenable. In this study, in order to satisfy the main objective of Riam Jerawi Reservoir, where the energy of 6 MW should be provided every month, a linear optimization model is applied for three objective functions such as maximizing total energy, maximizing minimum energy and minimizing energy shortage. In addition, a simulation model is also presented for comparison purpose particularly to emphasize some disadvantages of using this model. The results show that the optimum energy can be achieved by applying this optimization model where the continuity of reservoir volume is also satisfied. Meanwhile, the simulation model produces the rule curve, which cannot satisfy the continuity criterion. This optimization model is expected to be applied for other similar cases and give the optimum power rule curve for the related stakeholders.