IMIS

The 3 different types of hydrological models have been used recently to simulate the climate scenarios for Belgium and to assess the impact on hydrological extremes. All models simulate similar trends in the future flow extremes: higher as well as lower winter discharges can be expected for future winter periods; while summer discharges are expected to decrease (and will continue to decrease till 2100) due to climate change. When comparing the high and low flow changes between the models major differences were found for low flow minima, while the differences in high flow changes were rather limited. One reason is that precipitation is the dominant factor in high flow estimation, while for low flow modeling the model structure plays a more important role. The physically based MIKE SHE model envisages a considerable smaller decrease of the low flows than other models (HBV, NAM, WetSpa). This difference might be a consequence of the higher physical detail of the MIKE SHE model, which has a mechanism that more realistically accounts for groundwater flow. Simplifying the representation of the groundwater system by the (semi-)conceptual models might lead to discrepancies in the climate projections. FORMULIER: F-WL-PP10-1 Versie 02 GELDIG VANAF: 17/04/2009 However, it is not clear if the more complex and detailed models will lead to better hydrological predictions. In spite of the uncertainties among the applied models, the results indicate a wide range of changes in the discharge regime by 2100. The results should therefore be interpreted as trends and not as an accurate quantitative prediction of hydrological changes.