Load-frequency control problem of an interconnected hydropower system directly relates to the speed control of all synchronous generators in the network. The major goal of the speed control for such a case of complex power grids is to stabilize the rotational speed of the hydraulic turbines, thereby eliminating the fluctuations of both the system frequency and tie-line power flow resulting from random and continuous load changes. The final aim is to bring the network back to a stable state after load change appearances. This paper introduces an effective control scheme as an integration of the conventional PID regulators and the particle swarm optimization technique in dealing with this speed stabilization. Various simulation scenarios with different cases of load changes and fitness functions will be presented using MATLAB/Simulink package to demonstrate the applicability of the proposed control methodology over the traditional PID and fuzzy logic -based control counterparts.