The three hydrological models were built and calibrated using identical datasets for the Grote Nete catchment, a medium scaled catchment in Belgium. Each model was calibrated in by a trial-and –error process in which the information from the available discharge series (sub-flows and routing parameters) was fully employed. This allows to have a more realistic representation of the hydrological behaviour. Calibration was executed for historical observation data for a 3-year period, validation for another verification period of 3-years. The simulations were evaluated using multiple criteria in order to create plausible models that could target the different aspects of the observed series. These criteria were grouped into different classes and include (1) classical model performance tests, (2) performance tests on the flow extremes and (3) the control of the peak flow changes in relation to rainfall changes. After calibration all three conceptual models appear to be fairly adequate for the Grote Nete catchment when comparing the different objective functions. The models could capture well the overall runoff processes and streamflow dynamics. High as well as low flows are simulated reasonably well. Sub-flows and their volumes match closedly to the observations. None of the calibrated models is superior with respect to all performance measures considered.

FORMULIER: F-WL-PP10-1 Versie 02 GELDIG VANAF: 17/04/2009 These three optimally calibrated models were forced with the climate scenarios for Belgium (Ntegeka et al., 2008) for two future time slices (2050s and 2100s). All three models estimated similar general runoff changes inder the climate change scenarios for both the 2050s and 2100s: the low flow or drought problems will become more important with expected decreases of the low flow minima, while the flood risk predictions are highly uncertain for the future. The low flow problems are expected to be more severe by the 2100s than the 2050s. When comparing the simulated changes between the models, it is found that the hydrological impacts of climate change depend on the type of hydrological model used, and that the magnitude of this impact differs between high flow and low flow periods and between the applied scenarios.