Integrated modelling of the hydrological cycle in relation to global climate change

The main objectives of the project “INTEGRATED MODELLING OF THE HYDROLOGICAL CYCLE IN RELATION TO GLOBAL CLIMATE CHANGE” (CG/DD/08), are : - to gain knowledge in the understanding of the hydrological system at different time and space scales; - to develop and test an integrated holistic approach that can be able to assess the effects of climate change on the terrestrial hydrologic cycle and on water resources systems. The project is focused on two main aspects : 1) The comparison of models : 3 different types of models are used and compared : - the IRM/KMI uses a spatially non-discretized model (the IRMB model) and develops a spatially semi-discretized model (the SCHEME model); - the ILWM-KUL uses an existing spatially discretized integrated model, the MIKE-SHE model; - the HA-FUSAG, HG-KUL, LGIH-ULG and CE-ULG teams develop and use a spatially-discretized integrated model, composed of existing sub-models of land surface (soils), groundwater and surface water (the MOHISE model). These models have been tested and compared using the same data set, to assess their capabilities to represent the different phases of the terrestrial hydrological cycle (soil, groundwater, surface water). 2) The simulation of the impacts of climate changes on the terrestrial hydrological cycle : climate change scenarios (monthly changes of meteorological variables) were elaborated on the basis of the results of three GCM (Global Climate Models) experiments provided by the IPCC (International Panel on Climate Change) and tested on the test-basins. During the 4 years-project period (1997-2000), the scientific work has been devoted to the construction, integration and implementation of the models and related data bases. The models were tested, calibrated and validated on a few representative Belgian basins. The selected test-basins are the Gette basin (at Budingen : 600 km²), the Geer basin (at Kanne : 465 km²) and the Ourthe Orientale basin (at Mabompré : 319 km²). The results of this research demonstrate the ability of the models to simulate the functioning of the terrestrial hydrological cycle under the present climate and to take into account the major processes that occur in the soils, groundwater and surface water compartments. The models have been used to assess the effects of potential climate changes on the terrestrial hydrological cycle