The supply of environmental friendly and affordable electricity is one of the most important tasks for the energy industry and science in the future. Therefore we need tools and methods to seek economical-technical-environmental optimized solutions. With this master thesis a unit commitment model of the hydro power plants in Styria, Upper Austria and Lower Austria with more than 5 MW is developed and then combined with the existing HiREPS model for Austria and Germany. This combined HiREPS model is then used to analyse two scenarios of the Austrian and German power system. One with a 7% wind generation and one with 45% wind generation in terms of electricity demand. The thesis analyses in detail the operation of pumped storage and run-off hydro power plants for both scenarios. The second scenario allowed 10% of annual wind energy to be curtailed if this is beneficial for the operation of the power system. By allowing this it is possible to increase the wind share from 7% up to 45%. In the high wind scenario an emission reduction of 155mio tonCO2 per anno is achieved for Austria and Germany compared to the low wind scenario. This is a 60% reduction in CO2 emissions. The fossil and nuclear energy share is decreased by 39 percentage points. The hope is that this model will make important contributions for planning the next generation power system in Austria and in European Union and helps to promote the development of renewable energy systems.