"The role of 3D-hydraulics in habitat modelling of hydropeaking events"The study of ecological implications induced by hydropeaking requires to couple hydrodynamic models with habitat suitability models, in which hydrodynamic parameters are typically used to describe the physical habi-tat of indicator species. This article discusses the differences in habitat suitability assessment between a hy-drodynamic 2D and 3D CFD model as input for the habitat model CASiMiR. The accuracy of the hydraulic model is evaluated by comparing the model results with laboratory and field measurements. The case study is Valsura River located in the province of Bolzano, Italy. First results show that the habitat suitability index (HSI) using 2D or 3D hydrodynamic models can be significantly different. These differences can be ascribed to different reasons, such as a higher capability to depict the features of the flow field with highly variable and heterogeneous boundary conditions and the possibility to simulate the near bed hydrodynamic parame-ters, which are
relevant for certain target species. In particular, the HSI-values using 3D hydraulics lead to larger areas of highly suitable habitats compared to 2D simulations.