A methodology to analyze potential climate change impacts on hydrological extremes along rivers in Flanders (Belgium) has been developed. The results show that hydrological modelling techniques driven by climate modelling techniques and climate change scenarios enable a prediction of the long-term evolution of the hydrological system of the studied area. The hydrological system behaviour of the river Dender basin in the Scheldt River Basin District is modeled for an observed historical period and for a future change from the control period (1961-1990) to the predicted period (2071-2100) under forcing of a modified (predicted) climate. The climate induced impact on hydrological extremes is assessed through the comparison of key variables of the hydrological system for the two periods (e.g., runoff peaks, low flow values, overland flow and potential evapotranspiration).
The modelling procedure is completed through 24 climate model simulations highly resolute (derived from the PRUDENCE climate project), local scale lumped conceptual hydrological models (NAM of DHI), hydrodynamic models (MIKE11 of DHI) and models for topographical information (DEM: Digital Elevation Models) and risk calculation models covering the studied area. An appropriate downscaling method has been developed counting for variable statistical properties as intensity and frequency. Following this method, potential climate change scenarios for Flanders have been created based on sequences of low, mean and high variation factors for rainfall and potential evapotranspiration.
The modelling results show significant reduction of the low flows due to a considerable hydrological regime modification. As for hourly high flows (flood risk), the results range from increasing to decreasing depending on the climate change scenario and counting for a large uncertainty. Overland flow follows similar patterns as for the high flows while evapotranspiration shows systematic increase as a result of regional warming. A statistical method has been implemented for the quantification of the modelling uncertainties induced by the created climate change scenarios. Also a sensitivity analysis has been performed on the climate change scenarios to assess their degree of sensitivity to the process used to generate them and the degree of sensitivity of the hydrological response in turn.