Reevaluation of the Evaporation Method for Determining Hydraulic Functions in Unsaturated Soils
- Ole Wendroth ,
- W. Ehlers,
- H. Kage,
- J. W. Hopmans,
- J. Halbertsma and
- J. H. M. Wösten
Institut für Bodenforschung, ZALF, Wilhelm-Pieck-Str. 72, O-1278 Müncheberg, Germany
Institut für Pflanzenbau und Pflanzenzüchtung, Universität Göttingen, von Siebold-Str. 8, 3400 Göttingen, Germany
Hydrologic Science, Dep. of Land, Air and Water Resources, Univ. of California, Davis, CA 95616
The Winand Staring Centre for Integrated Land, Soil and Water Research, P.O. Box 125, 6700 AC Wageningen, The Netherlands
Understanding of soil water and solute transport processes requires knowledge of the soil hydraulic properties. A simple evaporation method for the determination of the hydraulic conductivity function and the water retention characteristic was developed and applied to a range of soils with different texture and structure. During evaporation from the top of a 6-cm-high soil core, soil water pressure head at 1.5 and 4.5 cm below the soil surface was measured with tensiometers several times. At the same time, evaporative water loss was determined by weighing the soil column. The procedure for calculation of hydraulic functions was evaluated via numerical simulations. Results from the numerical experiment confirm the underlying theory. A limitation of the evaporation method is the fact that, at water contents near saturation where hydraulic conductivity is high, hydraulic gradients cannot be determined with sufficient accuracy. Other measurement techniques are suggested that can supplement the evaporation method in the wet range.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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