Determining Unsaturated Hydraulic Conductivity from Tensiometric Data Alone

Abstract

AbstractA simplified functions approach, presented earlier, for determining the unsaturated hydraulic conductivity of soil from only the field tensiometric data taken during steady infiltration and draining, along with steady infiltration rate, is evaluated further. The assumptions concerning the form of soil‐water characteristics used in the operational equations of the method are recast in an integral form. These assumptions, as well as the intermediate steps in the computation, are tested on the experimental data for shallow as well as deeper depths of two new soil types. One of these soil types has a complex layered profile with texture varying from sandy to clayey, and the other a relatively uniform sandy profile. The final hydraulic conductivities obtained are compared with the values determined by the more rigorous Darcian analysis of the data for three sites. The results show that the assumptions made in the simplified method approximately hold for these soils at the depths tested, as deep as 1.9 and 1.35 m, respectively. The unsaturated hydraulic conductivity values determined by the proposed method are reasonably close to those values obtained by the detailed Darcian analysis for all depths. Large fluctuations in the tensiometric data for certain depths resulted in a large scatter in the conductivity values obtained by the detailed Darcian method, as well as greater discrepancy between the two methods. Practical validity of the basic assumptions of the method and the final results, for shallow as well as depper depths of the new contrasting soil profiles, constitutes significant information that provides confidence in the simplified approach.