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

Area of Science:

• Geophysics
• Soil Science
• Hydrology

Background:

• A significant gap exists between controlled laboratory experiments and complex field studies regarding soil moisture-electrical resistivity relationships.
• Existing methods for monitoring soil moisture dynamics in situ often lack spatial detail or repeatability.

Purpose of the Study:

• To evaluate the transferability of resistivity-soil moisture relations from laboratory to a more controlled outdoor environment.
• To assess the effectiveness of electric resistivity tomography (ERT) for monitoring soil moisture dynamics over an extended field period.

Main Methods:

• A 67-day field experiment was conducted at a homogeneous aeolian sand pasture site in The Netherlands.
• Electric resistivity tomography (ERT) was employed to monitor subsurface resistivity.
• ERT data were correlated with gravimetric soil moisture samples at multiple depths and time points.

Main Results:

• Correlations between ERT values and gravimetric soil moisture ranged from 0.43 to 0.73, with best results at 90 cm depth.
• Time-lapse ERT successfully identified rainfall infiltration patterns.
• Measurement noise was low (<3%) in the monitored soil profile, though some artefacts were observed, potentially due to tree roots and a nearby ditch.

Conclusions:

• ERT enables detailed spatial measurement of local soil moisture dynamics influenced by precipitation.
• Field applications of ERT, while valuable for spatial analysis, do not achieve the same accuracy as laboratory experiments.
• ERT is a suitable method for spatial soil moisture analysis where traditional probe or sample-based techniques are limited.