Imaging of Different Moisture States Inside an Undisturbed Soil Monolith with Georadar Tomography

Four different moisture states inside an undisturbed soil monolith, in our case a lysimeter, (cylindrical vessel of 1.2 m diameter and 1.5 m height) are imaged with georadar tomography. Two of the moisture states correspond to different steady state flow conditions which were adjusted by means of an irrigation device. Due to the all-around accessibility of the investigated lysimeter high resolution horizontal tomographic planes can be acquired. In this way, the lateral heterogeneity inside the lysimeter is investigated non-invasively, which is new for soil physical investigations. Based on the tomographic planes distinct lateral and vertical heterogeneous volumetric water content distributions are identified. According to the tomographic results lateral volumetric water content differences of up to 0.1 m3/m3 are encountered. In the vertical direction, volumetric water content changes of more than 0.1 m3/m3 are detected. This reflects the presence of different soil layers. Due to the different response of specific regions inside the lysimeter subject to the moisture state, supplementary information on the soil hydraulic properties is gathered.