Observation of volumetric water content and reflector depth with multichannel ground-penetrating radar in an artificial sand volume

Buchner, Jens S.; Kuhne, Alexander; Antz, Benny; Roth, Kurt; Wollschläger, Ute

doi:10.1109/iwagpr.2011.5963910

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…Reflection GPR is commonly used to image subsurface structures, but is also well suited to understanding hydrologic variability due to the strong dependence of EM wave velocities on soil volumetric water content (Topp et al, 1980). As a result, GPR has been adapted to monitor variability in hydrologic processes at multiple scales through time and space in a variety of contexts (Buchner et al, 2011;Busch et al, 2013;Guo et al, 2014;Haarder et al, 2011;Lunt et al, 2005;Mangel et al, 2012Mangel et al, , 2015bMangel et al, , 2017Moysey, 2010;Saintenoy et al, 2007;Steelman and Endres, 2010;Vellidis et al, 1990). Note that GPR methods are not applicable in media with relatively high electrical conductivity.…”

Section: Introductionmentioning

confidence: 99%

Reflection tomography of time-lapse GPR data for studying dynamic unsaturated flow phenomena

Mangel

Moysey

Bradford

2020

Hydrol. Earth Syst. Sci.

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Abstract. Ground-penetrating radar (GPR) reflection tomography algorithms allow non-invasive monitoring of water content changes resulting from flow in the vadose zone. The approach requires multi-offset GPR data that are traditionally slow to collect. We automate GPR data collection to reduce the survey time significantly, thereby making this approach to hydrologic monitoring feasible. The method was evaluated using numerical simulations and laboratory experiments that suggest reflection tomography can provide water content estimates to within 5 % vol vol−1–10 % vol vol−1 for the synthetic studies, whereas the empirical estimates were typically within 5 %–15 % of measurements from in situ probes. Both studies show larger observed errors in water content near the periphery of the wetting front, beyond which additional reflectors were not present to provide data coverage. Overall, coupling automated GPR data collection with reflection tomography provides a new method for informing models of subsurface hydrologic processes and a new method for determining transient 2-D soil moisture distributions.

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Section: Introductionmentioning

confidence: 99%

Reflection tomography of time-lapse GPR data for studying dynamic unsaturated flow phenomena

Mangel

Moysey

Bradford

2020

Hydrol. Earth Syst. Sci.

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“…Recent applications of time‐lapse reflection profiling to extract changes in vertical soil moisture information have been promising [i.e., Lunt et al , 2005; Wollschläger and Roth , 2005; Grote et al , 2005; Buchner et al , 2011]. This approach is less susceptible to measurement errors compared to NMO analysis; hence, it is potentially a more suitable technique to monitor highly variable soil conditions.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution ground‐penetrating radar monitoring of soil moisture dynamics: Field results, interpretation, and comparison with unsaturated flow model

Steelman

Endres

Jones

2012

Water Resources Research

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[1] Surface ground-penetrating radar (GPR) techniques have been used by a number of previous researchers to characterize soil moisture content in the vadose zone. However, limited temporal sampling and low resolution near the surface in these studies greatly impedes the quantitative analysis of vertical soil moisture distribution and its associated dynamics within the shallow subsurface. To further examine the capacity of surface GPR, we have undertaken an extensive 26 month field study using concurrent high-frequency (i.e., 900 MHz) reflection profiling and common-midpoint (CMP) soundings to quantitatively monitor soil moisture distribution and dynamics within the shallow vadose zone. This unprecedented data set allowed us to assess the concurrent use of these techniques over two contrasting annual cycles of soil conditions. Reflection profiles provided high-resolution traveltime data between four stratigraphic reflection events while cumulative results of the CMP sounding data set produced precise depth estimates for those reflecting interfaces, which were used to convert interval-traveltime data into soil moisture. The downward propagation of major infiltration episodes associated with seasonal and transient events are well resolved by the GPR data. The use of CMP soundings permitted the determination of direct ground wave velocities, which provided high-resolution information along the air-soil interface. This improved resolution enabled better characterization of short-duration wetting/drying and freezing/thawing processes, and permitted better evaluation of the nature of the coupling between shallow and deep moisture conditions. The nature of transient infiltration pulses, evapotranspiration episodes, and deep drainage patterns observed in the GPR data series were further examined by comparing them with a vertical soil moisture flow simulation based on the variably saturated model, HYDRUS-1D. Using laboratory-derived soil hydraulic property information from soil samples and a number of simplifying assumptions about the upper and lower-boundary condition, we were able to achieve very good agreement between measured and simulated soil moisture profiles without model calibration; this is a strong indication of the overall quality of the GPR-derived soil moisture estimates. The only notable difference between simulated values and GPR water content estimates occurred during extended dry soil conditions near the surface.

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Inverting surface GPR data using FDTD simulation and automatic detection of reflections to estimate subsurface water content and geometry

2012

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A new inversion scheme for common-offset ground-penetrating radar measurements at multiple antenna separations was proposed, which is intermediate between inverting of picked reflectors using ray-tracing and full-waveform inversion. The measurements are modeled similarly to the real data using 2D finite-difference time-domain simulations. These simulations are obtained with a parameterized model of the subsurface that consists of several layers with constant dielectric permittivity and an explicit representation of the layers’ interfaces. Then, reflections in the modeled and in the real data are detected automatically, and the reflections of interest of the real data are selected manually. The sum of squared residuals of the reflections’ traveltime and amplitude is iteratively minimized to estimate subsurface water content and geometry, i.e., the position and shape of the layer interfaces. The method was first tested with a synthetic data set and then applied to a real data set. The comparison of the method’s result with ground-truth data showed an agreement with the subsurface geometry within [Formula: see text] and with the water content, a difference less than [Formula: see text] volume.

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Observation of volumetric water content and reflector depth with multichannel ground-penetrating radar in an artificial sand volume

Cited by 4 publications

References 23 publications

Reflection tomography of time-lapse GPR data for studying dynamic unsaturated flow phenomena

Reflection tomography of time-lapse GPR data for studying dynamic unsaturated flow phenomena

High‐resolution ground‐penetrating radar monitoring of soil moisture dynamics: Field results, interpretation, and comparison with unsaturated flow model

Inverting surface GPR data using FDTD simulation and automatic detection of reflections to estimate subsurface water content and geometry

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