Simulation of the water budget and the river flows of the Rhone basin from1981 to 1994

As a first step toward the simulation of the continental water cycle at a r egional scale, the Phone basin simulation has been done from 1981 to 1994 u sing a soil-vegetation-atmosphere transfer model coupled with a hydrologica l model. A first study with a S km resolution and a 5 min time step was alr eady clone for one year (1987/1988) by Habets et al., 1999b (Habets F., Etc hevers P.. Golaz C., Leblois E.. Ledoux E., Martin E.. Noilhan J. and Ottle C. (1999): Simulation of the water budget and the river flows of the Rhone basin. J. of Geophysical Research, 104, n degrees D24, 31145-31172.) Becau se of the strong snow component of the basin, a detailled multi-layer snow model has been added to the original modelling system. This analysis covers a longer time period in order to examine the interannual variability; of c limatic conditions and streamflows. The observed atmospheric forcing has be en interpolated in time and space with a system especially adapted to the A lps mountains. Although only a limited calibration using observed discharge s was done, the model results compare fairly well with the daily observed d ischarges at 145 gauging stations located on the largest rivers of the catc hment. Poor results are obtained for sums of the smaller catchments (smalle r than 1000 km(2)), possibly because of inacurracies in the interpolated at mospheric forcing at small spatial scales. The evolution of the simulated s now pack is in good agreement with the daily observed snow depths at 24 hig h altitude stations located between 1500 and 3000 m in the Alps. Tile surfa ce water budget shows large spatial variations due both to vegetation and c limatic conditions. The interannual variability of the groundwater table is strongly related to the variability of precipitation with positive storage of water for wet years. (C) 2001 Elsevier Science B.V. All rights reserved .