When computing detailed soil moisture profiles during physical evaporation of soil moisture with help of generalized Darsy law, two functions are essential: retentivity function, and water conductivity function. The last one is often calculated with help of former one, using models of both functions, represented by van Genuchten-Mualem equations. One of parameters of this function is independently determined hydraulic conductivity K₀ .

The aim of this work is to check efficacy of using so determined this parameter in computations of detailed dynamics of moisture content field in evaporating soil.

K₀ of sieved heavy-loam podzolic soil, saturated overnight was determined by falling head method (K₀=0.035 cm/h). Retentivity function was determined experimentally. Parameters of the van Genuchten model were found by Markwardt technique with help of our MULTIPAR program. Several 20-cm long vertical cylindrical columns, closed at the bottom, were filled with the same soil at initial moisture content 28,2% by volume and were left to evaporate at 22^oC. Columns were weighed periodically up to 0.1 g. The technique secures high uniformity of moisture and bulk density distributions of all the columns, thus allowing to consider them as clones. The columns were dismantled after 0, 43, 67, 93, 121 and 168 h from start of the experiment, and moisture content in 1-cm ring sections was determined by drying. Using our program SIMDARS, the moisture content profiles were computed for the moments mentioned above and compared with experimental ones. There were evident discrepancies between experiment and calculations. After increasing K₀ up to 0.15 cm/h computed moisture content profiles closely followed experimental data for all the moments of the experiment.We feel that for such conditions the fitting coefficient in van Genuchten-Mualem water conductivity model should be determined either experimentally at smaller moisture content or found with help of the technique described in this paper.