Abstract : In order to study the water cycle at regional scale, Habets (1998) coupled the SVAT ISBA (developed by Meteo-France) with the hydrological model MODCOU (developed by the Ecole ds Mines de Paris) and applied them to the Rhone Basin for one year (1987/88). Due to the strong snow influence, the ssophisticated snow model Crocus has been included in the system in the framework of the present thesis. The simulation of the Rhone catchment has been extended for 14 years (from 1981 to 1994). The meteorological input data have been derived from the SAFRAN analysis, especially relevant for the mountainous areas. Since the discharge observations were not used for calibration, they were used for validation. Daily discharge observations were compared with simulation for 145 gauge stations located on the Rhone and main rivers of the basin. The simulated snowpack has also been validated by comparison with independent daily snow-depth observations provided for 24 sites. The water budget is very contrasted and puts into light three main ensembles : the northern snowy-rainy catchments (Saône, Doubs, Ain), the southern rainy catchements (low Durance, Ardèche) and the alpine catchments with a strong snowy component (Isère, Drac, high Durance). After its validation, the tool has been used to estimate the impact of a climate change on the main Rhone basin hydrological components. A particular attention was paid to an increase of the spatial resolution on the simulation of the high Durance snowy catchment.