A Short Review of the Methods for Determining Saturated Hydraulic Conductivity and a Comparison of Large and Small-Scale In-Situ Methods

Saturated hydraulic conductivity (KS) can be determined with correlation or hydraulic methods. Hydraulic methods can be classified as laboratory and large-scale or small-scale in-situ methods. Auger-hole, inversed auger-hole and Guelph Permeameter are the most common small-scale in-situ methods. The KS determined by small-scale methods has high spatial variability, has different values in the horizontal and vertical directions, and varies in different depths. Large scale methods enter an extensive soil body into the measurement process to eliminate variation. This paper aimed to evaluate the conventional field methods of measuring KS using the drain outflow as the reference method and investigate the effect of initial soil moisture on KS’s measuring accuracy by the inversed auger-hole method. Experiments were conducted in two 10-hectare research fields in south Khuzestan. KS was measured by the inversed auger-hole method in barren, dry soil before constructing the irrigation and drainage network. After the construction, the KS was measured by drainage water outflow as a large-scale method, as well as by auger-hole and inversed auger-hole methods in moist soil after several irrigations. The KS measured by conventional small-scale in-situ methods in Fields One and Two were respectively 42.5% and 62.9% lower than the drainage water outflow method. Considering the drain outflow as the reference method, there is no significant advantage between the auger-hole and inverse auger-hole methods. As in Field One, the values obtained from the auger-hole method were closer to the reference method, and in Field Two, the values obtained from the inversed auger-hole method were closer.