Evaluating the performance of a frequency-domain ground penetrating radar and multi-receiver electromagnetic induction sensor to map subsurface drainage in agricultural areas

Authors: KOGANTI, TRIVEN - Aarhus University; VAN DE VIJVER, ELLEN - Ghent University; Allred, Barry; GREVE, MOGENS - Aarhus University; RINGGAARD, JORGEN - Ramboll; IVERSEN, BO - Aarhus University

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2019
Publication Date: 5/15/2019
Citation: Koganti, T., Van De Vijver, E., Allred, B.J., Greve, M.H., Ringgaard, J., Iversen, B.V. 2019. Evaluating the performance of a frequency-domain ground penetrating radar and multi-receiver electromagnetic induction sensor to map subsurface drainage in agricultural areas. Proceedings of the 5th Global Workshop on Proximal Soil Sensing. 29-24.

Interpretive Summary:

Technical Abstract: Subsurface drainage systems remove excess water from the soil profile thereby improving crop yields in poorly drained farmland. Knowledge of the position of the buried drain lines is important: 1) to improve understanding of leaching and offsite release of nutrients and pesticides and 2) for the installation of a new set of drain lines between the old ones for enhanced soil water removal efficiency. Traditional methods of drainage mapping involve the use of tile probes and trenching equipment. While these can be effective, they are time-consuming, labor-intensive and may cause additional damage to the drainage pipes. Non-invasive geophysical soil sensors aid the collection of high-resolution spatially exhaustive data and therefore provide a potential solution to these problems. Previous research has focused on the use of time-domain ground penetrating radar (GPR), with variable success depending on local soil and hydrological conditions and the central frequency of the specific equipment employed. In this study, we present the use of a stepped-frequency continuous wave (SFCW) 3D-GPR (GeoScope Mk IV 3D-Radar with DXG1820 antenna array) instrument in combination with a single-frequency multi-receiver electromagnetic induction (EMI) sensor (DUALEM-21S). The 3D-GPR system offers more flexibility for application to different (sub)surface conditions due to the coverage of a wide frequency bandwidth. The DUALEM-21S sensor simultaneously provides information about the apparent electrical conductivity (ECa) and magnetic susceptibility (MSa) for four different soil volumes, corresponding to four different depths. This sensor combination was evaluated on nine different study sites with various soil types with textures ranging from sand to clay till. While high success rate was achieved in finding the tile drains at three sites (sandy, sandy loam, and organic soils) using the 3-D GPR instrument, the results at other six sites were less successful due to limited penetration of the 3D-GPR signal. Preliminary results suggests that the ECa measured by the DUALEM-21S sensor could be a useful proxy to evaluate the success that can be expected for the 3D-GPR instrument. The high attenuation of electromagnetic waves in highly conductive media limiting the penetration depth of the 3D-GPR instrument can explain the findings obtained in this research.