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Water distribution monitoring using an EMI-GPR-ERT approach

Traditionally, the soil water content (SWC) on agricultural test fields is monitored only point wise with soil samples, access tubes or buried time domain reflectometry (TDR). The aim of this subproject is to monitor SWC on the field scale in topsoil und subsoil with the help of non-invasive geophysical measurements like ground penetrating radar (GPR) and the bulk electrical conductivity (ECa) measured by electromagnetic induction (EMI) and/or electrical resistivity tomography (ERT).
Large-scale multi-configuration EMI characterization allows fast mapping of ECa with different sensing depths. However, since ECa is influenced by soil moisture, porosity, clay content, pore water conductivity and soil temperature, the conversion of ECa to soil moisture content is not straightforward. With the help of time-lapse measurements, regions of water depletion and water accumulation are investigated. The influence of the soil parameters obtained by other partners on the ECa will also be investigated. To map vertical soil moisture content distributions, ERT transects and/or inverted EMI data will be used.
Retrieving SWC from GPR is more straightforward and the dielectric permittivity can be converted to SWC using Topp’s equation. Recently, multi-channel GPR systems have become available enabling the identification of the groundwave, and reflections for several channels and making the determination of the dielectric permittivity, and SWC more straightforward. The combination of ERT, GPR and EMI results will enable us to extent the monitoring of the soil water content towards the field scale and to closely follow the effects of subsoil management on the SWC in different depths.

Contact:
Prof. Dr. Ir. Jan van der Kruk
Tel.: +49 2461 61 4077
Email: j.van.der.kruk@fz-juelich.de


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