IMPLICATIONS OF SPATIAL VARIABILITY OF SOIL PHYSICAL-PROPERTIES FOR SIMULATION OF EVAPORATION AT THE FIELD-SCALE

Soil water retention curves in eight soil profiles on a sandy soil wer e determined by field measurements of soil water content and soil wate r matric potential made during 19 days of continuous drying using time -domain-reflectometry and tensiometers. Evaporation from the different profiles was simulated using the retention curves and estimated unsat urated conductivity functions, meteorological data as driving variable s, and measured soil water matric potentials at 40 cm depths as the lo wer boundary condition. Good agreement was obtained between simulated and measured evaporation from different locations in the field. Areal mean evaporation obtained as the arithmetic mean of individual simulat ions was 2% smaller than the evaporation obtained using mean physical properties in one simulation. This difference was small compared to th e variation in simulated evaporation between individual locations (62- 142% of the mean evaporation).