How does the choice of the input hydrograph affect reservoir and dam design?

Abstract. Reservoir and dam design requires a detailed understanding of the entire input hydrograph rather than relying solely on peak discharge estimates. Input hydrographs are essential both for verification purposes to evaluate the peak attenuation capacity of the reservoir and for design purposes to define reservoir height, its volume and outlet structures. However, no universal guidelines exist for selecting the input hydrograph, leaving designers to navigate conflicting methodologies often without clear evidence of the advantages and drawbacks of different hydrographs. As a result, the choice of the input hydrograph is typically based on local regulations, introducing subjectivity and potential inconsistencies. This study investigates how sensitive reservoir and dam design is to the choice of the input hydrograph by quantifying the differences in reservoir key parameters, such as the maximum outflow discharge, maximum storable volume, and peak reduction effect. The analysis compares the results of the most commonly used input hydrographs and continuous time series routing. The study highlights the advantages and potential limitations of commonly used input hydrographs, particularly regarding their ability to represent hydrological conditions of the time series accurately. The findings of this study aim to offer a more conscious approach to hydrograph selection, potentially reducing subjectivity and improving the robustness of reservoir and dam design practices. Finally, the study seeks to address computational challenges associated with reservoir routing by identifying efficient yet reliable hydrograph options.