The relevance of measuring saturated hydraulic conductivity: Sensitivity analysis and functional evaluation

Abstract

The saturated hydraulic conductivity (Ks) is considered to be one of the main soil hydraulic properties to simulate water transport in the vadose zone, yet it is notoriously difficult to assess due to its large field-scale variability and sensitivity to preferential flow paths. With the increasing availability of convenient methods to measure the unsaturated hydraulic conductivity (Ku), the additional value of measuring Ks could be questioned. This study investigates the relevance of measuring Ks in two ways. Firstly, a sensitivity analysis was performed to evaluate which part of the hydraulic conductivity curve impacts the simulation of unsaturated water transport most. It was found that hydraulic conductivity curve between −10 cm and −1000 cm matric head was affecting the simulation more than at saturation. Secondly, a functional evaluation was performed by simulating water flow in six test fields according to three scenarios, in which the hydraulic properties were determined with the measured Ks and/or Ku. The simulation of saturation degree at three depths was the least accurate in the scenario where only Ks was measured. Remarkably, the most accurate simulation was found in the scenario with only the measured Ku. According to these results, measuring Ku would be of greater importance than measuring Ks for the simulation of water flow in the vadose zone.