Spatial Analysis and Scaling of Heterogeneous Hydraulic Properties in a Norwegian Agricultural Field.

Studying water flow in the vadose zone is complicated by the natural heterogeneous pathways present in all soils. Numerical models are often used to simulate flow in soils to aid in our understanding of heterogeneous flow processes and for problem-solving, but require some prior knowledge of the spatial distribution of soil hydraulic properties. Measurements of soil hydraulic properties must often be scaled to better fit the scale of the application. A multitude of scaling techniques for both the hydraulic properties and the spatial distribution of these properties in the model domain presents a difficult challenge for modeling water flow. A field experiment was conducted in a Norwegian agricultural in a 2 m x 1 m x 1m volume where there was evidence of heterogeneous inclusions in the soil. Twenty pairs of tensiometers and Time Domain Reflectometry (TDR) probes were installed with attention to the heterogeneous features to intensively investigate soil moisture distribution from May 2016 – October 2016. After the sensor data collection period, core samples were taken to measure hydraulic properties using a combination of laboratory techniques. Electrical Resistivity Tomography (ERT) data mapping the heterogeneous features was used to inform a model domain in HYDRUS-3D to simulate field conditions over the study period. We will discuss the effects of various scaling techniques on the hydraulic properties on the simulation of water flow, as well as analyze the spatial and temporal aspects of the field data in comparison to the laboratory measurements.