Analysis of the Hysteretic Hydraulic Properties of Unsaturated Soil

Knowledge of the unsaturated soil hydraulic properties is essential for modeling water flow and solute transport processes in variably saturated subsurface systems. Various experimental setups have been developed over the years to measure the hydraulic properties. We devised a relatively simple setup for simultaneous measurement of the water retention and unsaturated hydraulic conductivity curves using multistep flux (MSF) and hanging water column (HWC) experiments. Our focus was especially on medium- and coarse-textured sands having relatively narrow particle-size distributions as reflected by the van Genuchten-Mualem (VGM) hydraulic parameter n. Values of the VGM parameter n for some of the sands we used were as high as 15. We also measured the hydraulic properties using the HYPROP evaporation method. The MSF and HWC results showed excellent agreement, but deviated slightly from independent data obtained with the HYPROP measurement system.