Energy generation has always been a major stake in our economy and is all the more so with the increase in energy demand all over the world. In that context, hydroelectricity is considered one of the most important renewable energy sources. Hydropower optimization is a rich field that has been studied since hydropower dams exist. The major challenge in hydropower optimization is to use the available water to produce energy as efficiently as possible, since it is almost impossible to vary the physical installations once in place. Many challenges arise: uncertainty in the inflows, prices, outages, size of the problems, hydrological constraints, physical characteristics of the turbines and the power plants, and recently, the climate change context that tends to add complexity to the resolution, given that history does not repeat itself and the addition of extreme weather episodes. This paper intends to introduce the reader to the basic concepts of hydropower and present a survey of the field from an optimization point of view. The aim is to better understand the methodologies currently used, in order to assess if it is possible to shift or focus research in areas that may improve the current approaches.