Tracing lateral subsurface flow in layered soils by undisturbed monolith sampling, targeted laboratory experiments, and model‐based analysis

Lateral subsurface flow (LSF) is a phenomenon frequently occurring in the field induced by local water saturation along horizon boundaries under nonequilibrium conditions. However, observations of LSF undisturbed soils controlled irrigation laboratory are limited but needed for model improvement, prediction, and quantification LSF. We present method extracting an soil monolith boundary introduce experimental setup measurement device simulating rainfall. An test run was simulated using HYDRUS 2D. Water infiltrating into flowing either laterally or vertically through bottom could be separately captured suction discs at side bottom. Thus, clear distinction between lateral vertical possible. Pressure heads contents were recorded tensiometers frequency domain reflectometry (FDR) sensors distributed across regular two-dimensional, vertical, cross-sectional pattern. Sensor readings indicated presence conditions within monolith. Modeling results reproduce outflow constant irrigation, thus showing that steady-state can explained Richards equation van Genuchten–Mualem model. The presented used to improve verify models designed prediction onset including