Actual soil evaporation is simulated, in the water component, by three approaches: the CropSyst model, Campbell’s model (Campbell, 1985) and Ritchie’s model (Ritchie, 1972).

The CropSyst model is described here. The development of the other models is not yet completed in water component.

In Campbell’s equation the potential evaporation rate is determinant during the first stages of drying, when actual evaporation is equal to potential evaporation. The evaporation during second and third stages of drying is controlled by humidity at the evaporation surface and liquid flux in the soil.

Ritchie’s equation (Ritchie, 1972) calculates the actual soil evaporation rate, assuming two stages of soil evaporation. The first stage is limited by the energy available at the soil surface and continues until a soil-dependent upper limit is reached. As the upper limit of stage 1 is reached, soil evaporation enters stage 2. In stage 2, evaporation rate decreases proportionally to the time spent in stage 2.

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