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The recent increased number of black outs in the power system has been largely due to growing competition and deregulation among the power industry. Power systems are complex nonlinear systems and often exhibit low frequency electro-mechanical oscillations due to insufficient damping caused by severe operating conditions. This needs an advanced modeling and control techniques for effective control of power plants. In case of hydroelectric plant the hydro turbine is a non-linear, non-stationary multivariable system whose characteristics vary significantly with the unpredictable load on it and this presents a difficulty in designing an efficient and reliable controller. A conservatively designed control fails to perform as expected. Keeping this in mind, hydro plant control is an application area with an interesting set of problems for control engineering people. Mainly some of these problems focus towards regulation of turbine with large load variation in the power system. These problems have not been adequately solved and continue to pose challenges to the control community. In this review paper, the authors have tried to broadly categorize the research work done so far on the basis of hydro plant model development and its controller design under different sections. A substantial number of relevant research papers can be found on the plant modeling, design aspects of control methodologies and their performance study.