Abstract. Hydrological models are the decisive tools to evaluate the effect of global change upon the water cycle. But the applied hydrological models have to be a trade-off between their degree of complexity and manageable structures and data requirements. This paper compares the advantages and disadvantages of integrating a spatially-distributed process-based groundwater flow model in the context of the calibration of a catchment runoff concentration model. The multi-objective optimisation and the GLUE method are used to analyse the performance and the parameter identifiability of both model structures.