Chapter 7 - Using ground-penetrating radar to map agricultural subsurface drainage systems for economic and environmental benefit

Authors: Allred, Barry; KOGANTI, TRIVEN - Aarhus University

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/10/2022
Publication Date: 3/15/2023
Citation: Allred, B.J., Koganti, T. 2023. Chapter 7 - Using ground-penetrating radar to map agricultural subsurface drainage systems for economic and environmental benefit. In: Advances in Sensor Technology for Sustainable Crop Production. Editors: Craig Lobsey and Asim Biswas. Burleigh Dodds Science Publishing Limited. Sawston, Cambridge, UK. pages 195-219.

Interpretive Summary: Agricultural subsurface drainage systems remove excess soil water, thereby improving crop yields. Farmers often need to repair or retrofit these drainage system, but in order to do so, maps of the pre-existing drain lines are required. Environmental risk assessment regarding farm field discharge of nitrate/phosphate via subsurface drainage can be improved through knowledge of the installed drainage pipe network, including extent of coverage and drain line spacing distance. The present methods for finding drainage pipes involving hand-held tile probes or trenching equipment are time-consuming, tedious, and cause pipe damage. Regardless of whether the need is economic or environmental, there is a strong demand for effective, efficient, and nondestructive methods to map buried drainage pipes. Ground penetrating radar (GPR) may provide part of the solution to this problem. This book chapter focused on summarizing the research conducted over the past twenty years on mapping subsurface drainage systems with GPR. When evaluated with three other proximal soil sensing methods (magnetometry, electromagnetic induction, and resistivity), GPR was the only one exhibiting capability for drainage pipe detection. Factors impacting GPR drainage pipe detection were then assessed (i.e. equipment and survey set-up, site conditions, and computer processing). Investigations that followed focused on GPR drainage pipe response effects due to pipe conditions (air-, water-, and/or soil-filled) and antenna orientation relative to drain line directional trend. Highlighted next were GPR drainage mapping efficiency improvements through integration with Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) technology and use of a multichannel, stepped-frequency, continuous wave 3D-GPR system. Discussed last was the complimentary employment of GPR and unmanned aerial vehicle (UAV) imagery for drainage system characterization. The research described in this chapter certainly indicates that GPR can play an important role with respect to mapping subsurface drainage systems across agricultural landscapes.

Technical Abstract: Due to economic and environmental considerations, there exists a need for effective, efficient, and nondestructive methods for locating buried agricultural drainage pipes. Ground penetrating radar (GPR), a proximal soil sensing method, can potentially provide a means for drain line detection. This chapter will detail the evolution of research, through a series of studies conducted over the past twenty years, which focused on farm field mapping of subsurface drainage systems using GPR. Following the Section 1 Introduction, the studies to be described in sequence include: (Section 2) evaluation of GPR against other proximal soil sensing methods; (Section 3) factors potentially impacting GPR drainage pipe detection; (Section 4) GPR assessment of agricultural drainage pipe conditions and associated functionality implications; (Section 5) effects of GPR antenna orientation relative to drain line directional trend; (Section 6) integration of GPR with Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) technology; (Section 7) drainage mapping with a multichannel, stepped-frequency, continuous wave 3D-GPR system; and (Section 8) complimentary employment of GPR and unmanned aerial vehicle (UAV) imagery for drainage system characterization. The chapter will conclude with a summary and recommendations for future research.