Hydro-meteorological modelling of the Rhone basin: general presentation and objectives

The paper presents the French national effort undertaken these 5 last years in order to build a hydrological modelisation of the Rhone catchment, coupling the surface and the atmosphere at regional scale. The modelling strategy is based on the coupling of the operational surface model (the ISBA SVAT scheme), the snow model (CROCUS) of Meteo-France and the distributed hydrological model MODCOU developed at Centre d'Informatique Géologique de l'Ecole Nationale Supérieure des Mines de Paris (CIG/ENSMP). As a first step, the coupled model (called in the following CIRSE) uses prescribed atmospheric forcing deduced from meteorological analysis. Several high resolution databases on a fourteen-year period have been constituted. The first part of the article presents the meteorological forcing database, the discharges database and the soil and vegetation maps. Then, the first results of CIRSE model and its validation on the riverflows are shown. As the coupled model was proved to be able to simulate present hydrology characteristics, it was finally used to conduct a preliminary climate change impact study. The impact of surface air temperature and precipitation variations on the hydrological cycle in a doubling CO₂ scenario simulated by the Meteo-France climate General Circulation Model (GCM) are shown.