Evaluation of porous medium hydraulic properties using experimental methods and RETC code

Two experimental procedures were used to determine both hydraulic properties, soil water retention theta(h) curve and unsaturated hydraulic conductivity K(theta), of a sand sample. Knowledge of hydraulic properties is essential, since they generally control soil water dynamics. A steadystate laboratory method was used for the simultaneous determination of theta(h) and K(theta). A one-step outflow method was used for the determination of diffusivity D(theta) and subsequently K(theta) from soil water retention data which were measured independently on the same sample and using the same apparatus. The comparison of K(theta) measured values from the above-mentioned methods showed very good agreement of the results. Also, the comparison between the experimental K(theta) and theta(h) functions and the predictions obtained using retention curve (RETC) code by simultaneous fit of experimental soil water retention and hydraulic conductivity data from outflow data, assuming the Mualemvan Genuchten model, showed very good agreement. It is noted that the main disadvantage of the one-step outflow method is the weakness to predict K(theta) values near saturation. This disadvantage could be overcome using RETC code with the above procedures, since the K(theta) values between the predictive approach and the steady-state method were similar.