This study describes the implementation of three different models for detailed analysis of impacts on the regional power system for different hydrological years. The region includes countries Slovenia, Croatia, Serbia, Bosnia and Herzegovina, Montenegro, Kosovo, North Macedonia, Albania and Greece. Combining the hydrological LISFLOOD model with Dispa-SET models for simulation of the regional power system, three scenarios for dry, average and wet year were studied to investigate the regional power system output for different hydrological conditions. The first part of the study included gathering data needed for detailed representation of regional power system participants and analysis of data from the LISFLOOD model provided by the European Commission’s Joint Research Centre (JRC). Data on regional power systems were obtained from available databases and documentation published by regional TSO’s. Details on region hydrology and power system of each country is described in the first two sections. Three mentioned models are in more detail described in Section 3. The LISFLOOD model is included in the study in the form of its results that are needed as input data for Dispa-SET models. Water inflows are crucial for a successful run of Dispa-SET models that can be divided into Dispa-SET Medium-Term Hydrothermal Coordination model (Dispa-SET MTHC) and Dispa-SET Unit Commitment and Dispatch model (Dispa-SET UCD). Dispa-SET MTHC model is used to in detail represent hydropower generation of each unit included in the study. Results in the form of hydropower generation for run-of-river units and reservoir levels of hydropower units with accumulations are used as input data for Dispa-SET UCD model. Besides power generation, results from UCD model include economical, commitment and power dispatch values for each unit and aggregated by country or region. The model was validated based on the hydropower generation for the reference year (2015). Results on three different hydrological years, 2007, 2015 and 2010 used as dry, average and wet year, respectively, are shown in Section 6. Region hydropower generation was compared to available statistical data from ENTSO-E and International Energy Agency. The study shows model results on power system operation for different hydrological conditions.