A mathematical model for the computation of evaporation from bare sali
ne soils is presented. Moisture flow and heat transport equations in t
he partially saturated zone of the soil are coupled at the soil surfac
e with a lower atmosphere boundary layer model. The transport model co
nsiders multicomponent salt migration. The flow equation accounts for
osmotic flux due to the presence of ion species in the soil solution.
Nonlinear one-dimensional equations were solved using fully implicit f
inite difference schemes. The soil part of the model was tested using
experimental data of water and solute redistribution under temperature
gradients in sealed soil columns. In order to demonstrate the effect
of soil salinity on the evaporation, the problem of water infiltration
into soil with initially low water content and its subsequent evapora
tion was considered. Results show a significant effect of osmotic pres
sure gradients on predicted evaporation.