Evaluation of a water balance model using data for bare soil and crop surfaces in Middle Europe

This paper compares the results of simulations and measurements of evapotranspiration from cultivated fields in Middle Europe. The modelling system THESEUS (i.e. toolbox for hydro-ecological simulation and evaluation utilities) from Wegehenkel (1997a, 2000) was used in this study. Evapotranspiration was also calculated from the latent heat flux density (LE) measured using a modified Bowen ratio method. The model, as well as the modification of the Bowen ratio procedure are described. Heat balance components for eight measurement periods (81 days) were used in the comparison. There was good agreement between model simulations and measurements. The average relative error in evapotranspiration estimation by the model was about 10% for time of integration of few days, and the error decreases with the increase of integration time. The error is smaller for higher daily rates of evapotranspiration. (C) 2001 Elsevier Science B.V. All rights reserved.