Author(s): Dina Pirone; Luigi Cimorelli; Andrea D’Aniello; Daniele Martino; Domenico Pianese
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Keywords: Chicago-storm Peak-discharge Dams Variational Approach Reservoir Routing
Abstract: Flood control reservoir design requires a combination of hydrological and hydraulic modelling techniques. Hydrological methods estimate the discharge from the basin upstream of the reservoir (i. e., inflow hydrographs), while hydraulic methods (reservoir routing) simulate how hydrographs propagate through the reservoir, thus computing the maximum outflow discharge and the stored water volume. This study investigates whether the hydrological methods influence the evaluation of the maximum outflow discharge from reservoirs of different configurations. Under the ideal assumptions of linearity and stationarity in the rainfall-runoff process, two methods are compared to estimate the inflow hydrographs and, thus, the outflow discharge from the reservoir: the Chicago storm-based method and the variational approach. On the one hand, the Chicago storm-based method considers a single design hyetograph that aligns with the Identity Duration Frequency (IDF) curve parameters and converts it into the design inflow hydrograph, according to the convolution theory, to evaluate the outflow discharge from the reservoir. On the other hand, the variational approach considers several rectangular hyetographs with uniform intensity during the duration extracted from the IDF curves, transforms them into the corresponding hydrographs and searches for the critical one that provides the maximum outflow discharge from the reservoir. The two methods are compared across 96 reservoir configurations characterised by varying outlet structures and geometries. Results indicate that the two methods produce similar estimates, with a mean percentage error between outflow discharge of less than 2 % and a mean percentage error between the total stored volume of less than 6%. This result demonstrates that both approaches are robust and reliable for outflow discharge for diverse reservoir configurations. Therefore, depending on the design process’s specific requirements or data availability, either method can be effectively utilised, offering flexibility in flood-control reservoir design.
Year: 2025