Monitoring Soil Moisture Dynamics Using Electrical Resistivity Tomography under Homogeneous Field Conditions

Abstract

There is a gap between lab experiments where resistivity–soil moisture relations are generally very good and field studies in complex environmental settings where relations are always less good and complicated by many factors. An experiment was designed where environmental settings are more controlled, the best outside laboratory, to assess the transferability from lab to outdoor. A field experiment was carried out to evaluate the use of electric resistivity tomography (ERT) for monitoring soil moisture dynamics over a period of 67 days. A homogeneous site in the central part of The Netherlands was selected consisting of grass pasture on an aeolian sand soil profile. ERT values were correlated to gravimetric soil moisture samples for five depths at three different dates. Correlations ranged from 0.43 to 0.73 and were best for a soil depth of 90 cm. Resistivity patterns over time (time-lapse ERT) were analyzed and related to rainfall events where rainfall infiltration patterns could be identified. Duplicate ERT measurements showed that the noise level of the instrument and measurements is low and generally below 3% for the soil profile below the mixed layer but above the groundwater. Although the majority of the measured resistivity patterns could be well explained, some artefacts and dynamics were more difficult to clarify, even so in this homogeneous field situation. The presence of an oak tree with its root structure and a ditch with surface water with higher conductivity may have an impact on the resistivity pattern in the soil profile and over time. We conclude that ERT allows for detailed spatial measurement of local soil moisture dynamics resulting from precipitation although field experiments do not yield accuracies similar to laboratory experiments. ERT approaches are suitable for detailed spatial analyses where probe or sample-based methods are limited in reach or repeatability.

Soil Water Content Prediction Using Electrical Resistivity Tomography (ERT) in Mediterranean Tree Orchard Soils

“…In this research, the ERT profiles were carried out very close to the trees, thus it is very likely that these anomalies resulted from the presence of roots. According to Giambastiani et al [ 38 ], the presence of roots significantly affects ERT results; moreover, there are significant variations in resistivity ranges depending on the type of tree and on measurement conditions (wet or dry) [ 39 , 40 , 41 ].…”

Capabilities and limitations of electrical resistivity tomography for mapping and surveying hillfort fortifications

“…Within selected hillforts, tests of electrode array and electrode spacing were performed (see Section 3.1). Rainfall and soil moisture effects on ERT data were neglected, because significant seasonal changes of soil moisture are usually observed to depth ~0.90 m (de Jong et al, 2020), but the shallowest data with 1 m electrode spacing were collected from depth of 0.60 m. Thus, soil moisture most likely does not affect results on metre‐sized and thick and/or deep defensive structures. Magnetometry surveys were measured by a Scintrex SM‐4G caesium magnetometer (Scintrex, Concord, ON, Canada) registering the vertical gradient of total magnetic field.…”

3D Modelling of Iron Sand Using Geoelectrical Resistivity Method with Wenner Array in Ulakan Tapakis, Padang Pariaman, West Sumatra

“…Based on the research objectives, the method used is the mapping method. The resistivity mapping method is a resistivity method that aims to study variations in the resistivity of the subsurface horizontally [4].…”