Monitoring Water Migration Processes in Cracking Clay Soil with Depth Profiles of Square Array Resistivity Measurements

Depth profiles of 0.05 m spaced coplanar horizontal square arrays are installed in a weighing lysimeter filled with cracking clay soil. During two water applications with different application methods and intensities, time lapse series of electrical resistivity measurements with the α, β, and γ square arrays are collected and the anisotropy index (AI) and mean apparent resistivity (ρam) are calculated for each measurement depth. Differences in the pre irrigation soil moisture content and cracking intensity were identified by the initial AI and ρam values and were consistent with the initial weight of the lysimeter and the observed surface cracks intensity. Differences in the progression of the AI and ρam values during the two irrigation events highlighted different water migration processes in the soil profile, which was supported by differences in the drainage regime out of the lysimeter. The results show that time series of AI and ρam depth profiles can be used to distinguish between soil moisture and cracking stages as well as water migration processes within a soil profile, which will provide valuable insight during the investigation of the complex water migration processes in cracking clay soils.