Estimation of catchment-scale water-balance with a soil-vegetation-atmosphere transfer model

Catchments with a small elevation range and relatively long dry periods in high radiation conditions may be described as an array of vertical one-dimensional pathways for water and energy. Such a representation enhances the ability of SVAT modeling to simulate mass exchanges across the catchment. This note reports on a comparison of a Soil-Vegetation-Atmosphere Transfer (SVAT) model (Braud et al., 1995), a deterministic hydrological model (Dawes and Hatton, 1993) and a stochastic hydrological model (Sivapalan and Woods, 1995; Kalma et al., 1995). The original version of the SVAT model only considers vertical transport and this one-dimensional representation must be aggregated to describe the entire catchment. Therefore, two new versions have been developed: a deterministic SVAT model which sub-divides the catchment into 40 sub-regions linked by surface flow, and a stochastic model which provides a distribution of the output fluxes as related to the spatial distribution of initial water content and/or soil properties. All simulations have been made for a 60-day period.