Author(s): Parisa Khorsandi Kuhanestani; Anouk Bomers; Martijn Booij; Jord Warmink; Suzanne Hulscher

Linked Author(s): parisa Khorsandi Kuhanestani, Anouk Bomers, Jord Warmink

Keywords: Hydraulic river modelling; High flow; Low flow; Calibration; Roughness

Abstract: Global climate change affects all aspects of river processes. It is expected that discharge extremes will occur more often in the future and that the possibility of having discharge extremes in terms of high and low flows in a shorter period will increase. More specifically, for the Rhine River in Germany and the Netherlands, high discharges in winter are expected to become more severe, whereas low flows will occur more often and over a more extended period in summer and autumn. Given these changes in climate conditions, the question arises whether it is possible to have an integrated hydraulic modelling approach to simulate high and low flows in rivers. One of the advantages of a single model for low and high flows is the tendency towards integrated river management. For example, the implications of measures targeted to high flows should not have negative consequences for low flows and vice versa. Currently, the calibration procedure is one of the reasons to employ two separate models instead of one calibrated model. Calibration means minimizing the errors between simulated and observed water levels by modifying model parameters for a specific situation. These errors could be caused by e.g. uncertainties in data and mesh discretization in two dimensional hydraulic models. In this regard, to develop a calibration approach for a single model for both high and low flows, the most crucial issue is understanding the main differences between high flow and low flow model characteristics such as mesh coverage and how these characteristics affect the calibration process. In this study, we evaluated the performance of models calibrated on high flows with different calibration methods for low flow conditions and vice versa. We applied the most commonly used calibration methods by calibrating the main channel roughness such that differences between measured and modelled water levels are minimal. The results show the differences between high flow and low flow calibration by means of calibrated parameter values and performance metrics. A model of the Waal River (a bifurcation of the Rhine River) in the Netherlands is used as a case study.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022786

Year: 2022