The role of the initial soil water content in the determination of unsaturated soil hydraulic conductivity using a tension infiltrometer

The unsaturated hydraulic conductivity K(h) is a key soil parameter governing the water and solute transportation processes. The course of this function depends on the geometry of the pores which is determined by the soil's physical and chemical properties. Many studies focus on the comparison of soil hydraulic conductivity under different conditions. Despite the recent progress in this research field, no reference method for measuring the K(h) in situ exists. This study focuses on the effect of the initial water content of the soil as a factor influencing the measured K(h). The study was performed in situ over short time period and with several replications close to each other in order to reduce the effect of other factors which could cause variations. Two tension infiltrometers were used and compared: A Hood infiltrometer IL-2700 and a Minidisk infiltrometer. Three different levels of initial water content (dry, medium wet and wet) were applied for each of the two infiltrometers, and three pressure heads (-0.5; -1 and -3 cm) for each measurement. According to the results, the Minidisk infiltrometer showed significant sensitivity to the initial water content, while measurements performed using the Hood infiltrometer were more stable.