Simulation of Evapotranspiration and Vadose Zone Hydrology Using Limited Soil Data: A Comparison of Four Computer Models

Four ecohydrological models (Mate, SPA, Vadose and WaSim) of differing complexity were compared for their precision in predicting evapotranspiration (ET) and drainage in 2007, when key data needed for quantifying soil parameters were limited. With exception of Mate, the other three predicted annual evapotranspiration within 10% of the measured data; the under-prediction of ET by Mate, which was also the only model not to predict drainage, often resulted in the over-estimation of the amount of water stored in the soil. The other three models all over-predicted drainage, which suggested that our approximations of the soil parameters reduced the water holding capacity, while enhancing the hydraulic conductivity, of the soil. This study demonstrates the significance of precisely quantifying the key soil parameters for the models if other key components, rather than just ET, are of interest. It also shows the potential of these models in providing first approximations of the components of the soil-water balance.