Planning the use of large reservoirs for electricity generation is a very demanding and complex problem. In addition to the requirements and limitations resulting from the search for an optimal operating regime for energy purposes, planning is also conditioned by the requirements of other water users and the requirements of flood protection. The subject of this study primarily includes examining the possibility of defining a new model of use and management of the Busko Blato reservoir and the Orlovac hydropower system (HES) as a whole, since data on the achieved production in the previous period of use of the reservoir show very large seepage losses, depending on the elevation.