Subsurface drainage systems are commonly used to remove surplus water from the soil profile of a poorly drained farmland. Traditional methods for drainage mapping involve the use of tile probes and trenching equipment that are time-consuming, labor-intensive, and invasive, thereby entailing an inherent risk of damaging the drainpipes. Effective and efficient methods are needed in order to map the buried drain lines: (1) to comprehend the processes 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 to enhance the soil water removal. Non-invasive geophysical soil sensors provide a potential alternative solution. Previous research has mainly showcased the use of time-domain ground penetrating radar, with variable success, depending on local soil and hydrological conditions and the central frequency of the specific equipment used. The objectives of this study were: (1) to test the use of a stepped-frequency continuous wave three-dimensional ground penetrating radar (3D-GPR) with a wide antenna array for subsurface drainage mapping and (2) to evaluate its performance with the use of a single-frequency multi-receiver electromagnetic induction (EMI) sensor in-combination. This sensor combination was evaluated on twelve different study sites with various soil types with textures ranging from sand to clay till. While the 3D-GPR showed a high success rate in finding the drainpipes at five sites (sandy, sandy loam, loamy sand, and organic topsoils), the results at the other seven sites were less successful due to the limited penetration depth of the 3D-GPR signal. The results suggest that the electrical conductivity estimates produced by the inversion of apparent electrical conductivity data measured by the EMI sensor could be a useful proxy for explaining the success achieved by the 3D-GPR in finding the drain lines.

中文翻译：

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使用频域探地雷达对农业地下排水系统进行制图，并使用单频多接收器电磁感应仪评估其性能。

地下排水系统通常用于从排水不良的农田的土壤剖面中去除多余的水。传统的排水图绘制方法涉及使用瓷砖探针和挖沟设备，它们费时，费力且具有侵入性，因此存在损坏排水管的固有风险。需要有效而有效的方法来绘制埋没的排水管线图：（1）理解养分和农药的淋洗和异地释放过程；（2）在旧的排水管线之间安装一套新的排水管线。增强土壤除水能力。非侵入性地球物理土壤传感器提供了潜在的替代解决方案。先前的研究主要展示了时域探地雷达的使用，但取得了不同的成功，取决于当地的土壤和水文条件以及所用特定设备的中心频率。这项研究的目的是：（1）测试具有宽天线阵列的步进频率连续波三维地面穿透雷达（3D-GPR）在地下排水测绘中的使用；（2）评估其性能结合使用单频多接收器电磁感应（EMI）传感器。在十二种不同的研究地点对这种传感器组合进行了评估，研究地点的土壤类型从沙子到黏土直到土壤。尽管3D-GPR在五个位置（沙质，砂壤土，壤质砂和有机表土）找到排水管的成功率很高，但由于3D的渗透深度有限，其他七个位置的排水效果不佳-GPR信号。