ELIMINATING THE EFFECT OF TEMPERATURE FROM UNSATURATED SOIL HYDRAULIC FUNCTIONS

The effect of temperature in soil-water transfer studies is usually neglected. However, experimental research has shown that there is a strong temperature effect on the characteristic soil hydraulic functions, such as the matric potential versus water content relationship, h(theta), and the hydraulic conductivity versus water content relationship, K(theta). The objective of this study was to examine whether this effect can be isolated and explained. For this purpose, experimental h(theta) and K(theta) values from two different sandy soils at temperatures of 20,8 and 3-degrees-C, were directly compared with predictions obtained by both the surface-tension viscous-flow model of soil moisture movement (STVF) and the empirical Gain factor model extended to include the K(theta) relationship. Results showed that the predictive efficiency of the STVF method depends upon the soil type. For fine-textured material the Gain factor model seemed to perform satisfactorily. Finally, it was shown that unique normalized functions of both characteristic soil hydraulic properties, independent of temperature, can always be obtained.