In the present study the authors present a novel, hybrid optimization technique for optimal reservoir planning and management. The new method couples Harmony Search Algorithm (HSA) with Incremental Dynamic Programming (IDP), resulting to the creation of an effective, hybrid optimization technique. The HSA algorithm creates feasible initial trajectories for the IDP method, an alteration that results to better and quicker generation of initial solutions. After test-runs it occurred that the created hybrid Algorithm shows an improved performance and converges quicker to better solutions. The designed hybrid algorithm has been applied for the definition of the optimal reservoir operation policy in Huong-Dien hydroelectric dam of Hue Basin, Vietnam. The created model has encompassed the Reservoir's water balance equation and also aimed to prevent flood events, cover irrigation-water demands and maximize hydroelectric energy production. The results of the proposed hybrid method have been compared with those obtained by the simple HSA method. In that way it has been shown that the novel hybrid technique is a robust tool and successfully located such values of the decision variables that result to an increased Hydroelectric energy benefit, while satisfying the specified constraints for environmental protection and flood control. Therefore, its application to similar water resources management problems could be efficient and successful.