Comparison of two hydrological simulations of the Rhone basin

The objective of the GEWEX/Rhone project is to develop a regional model of the surface energy and water cycles, coupled with a macroscale hydrological model within the Rhone basin. TNO methods have been used: the Standard MOD COU model (SM) and CIRSE. SM computes the water balance with a daily time s tep using production functions consisting of 3 reservoirs. CIRSE is compris ed of the ISBA surface scheme and the detailed CROCUS snow scheme. It solve s the energy and water balances with a 5-minute time step. Both methods use the same model for the runoff routing and the water table evolution. This article presents the application of the 2 methods over the French part of t he Rhone basin (86500 km2), for the 11-year period August 1981 to July 1995 . Both models give satisfying results. SM, which was calibrated over a 3-ye ar period, obtains the best results in terms of daily efficiency. However, the simulated total annual discharge is closer Is the observations with CIR SE than with SM. This is due, to the representation of the vegetation cycle and probably to a more realistic description of the soil moisture and evap oration in CIRSE. (C) 2001 Elsevier Science Ltd. All rights reserved.