SIMULATION OF THE WATER BUDGET AND THE RIVER

FLOWS OF THE RHONE BASIN FROM 1981-1994

by P. Etchevers, C. Golaz, and F. Habets

    As a first step toward the simulation of the continental water cycle at a regional scale, simulations using a Soil-Vegetation-Atmosphere Transfer (SVAT) model coupled with a hydrological model was done on the Rhone basin for one year (1987-1988). Because of the strong snow component of the basin, a detailed multi-layer snow model has been added to the original modeling system. The present analysis covers a longer time period in order to examine the inter-annual variability of climatic conditions and streamflows. The Rhone basin simulation has been extended to 14 years (from 1981-1994). The observed atmospheric forcing has been interpolated in time and space with a system especially adapted to the Alps mountains. Although only a limited calibration using observed discharges was done, the model results compare fairly well with the daily observed discharges at 145 gauging stations located on the largest rivers of the catchment. Poor results are obtained for some of the smaller catchments (smaller than 1000 km squared), possibly because of inaccuracies in the interpolated atmospheric forcing at small spatial scales. The evolution of the simulated snow pack is in good agreement with the daily observed snow depths at 24 high altitude stations located between 1500 and 3000 m in the Alps. The surface water budget shows large spatial variations due both to vegetation and climatic conditions. The inter-annual variability of the water table is strongly related to the variability of precipitation with positive storage of water for wet years.

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