Hydropower plants are still the most important renewable energy resource worldwide. Hydropower is also the most efficient electricity production and has a very high flexibility in combination with reservoirs. Nevertheless, the construction of hydropower plants, especially in the case of large schemes, requires high investments with long payback periods. Thus, future uncertainties have to be considered in early design stages in order to obtain robust and flexible projects with high resilience. With his research, Dr. Felix Oberrauch made a significant contribution by showing how hydropower projects have to be designed with advanced methods which allow to take into account the future uncertainties. Very large hydropower project developments are often in the public focus associating them with significant cost overrun and bad performance. With the slogan “Small is beautiful” in the public awareness often preference is given to the development of small hydropower. Dr. Oberrauch analyzed for the first time in a systematic way with a coherent sample of realized projects the uncertainties of small and large hydropower projects in Switzerland regarding cost overrun and production overestimation. He could show that small hydropower projects, on average, can have similar range of cost overrun as large projects. However, the probability that small projects exceed the estimated costs is smaller than for large projects. Nevertheless, the sample analysis revealed that small hydropower projects have a tendency to more extreme cost overruns than large facilities. Based on the Swiss hydropower dataset Dr. Oberrauch showed how the uncertainties of construction cost and energy production forecasts can be implemented in the economical evaluation of a project. As novel contribution for the engineering practice Dr. Oberrauch presented a new framework which allows a straightforward selection of the design objective and the required design method in order to consider uncertainties in early design stages of hydropower projects. He showed how the methods of Robust Decision Making, Info-Gap Decision Theory and Flexible Design have to be formulated and applied to a real hydropower project. Dr. Oberrauch discusses in detail the value and the limitations of each approach and gives final recommendations for their application.