Coupling time-lapse ground penetrating radar surveys and infiltration experiments to characterize two types of non-uniform flow

Abstract. High-resolution time-lapse ground-penetrating radar (GPR) observations of advancing and retreating water tables can yield a wealth of information about near-surface water content dynamics. In this study, we present and analyze a series of imbibition, drainage and infiltration experiments that have been carried out at our artificial ASSESS test site and observed with surface-based GPR. The test site features a complicated but known subsurface architecture constructed with three different kinds of sand. It allows the study of soil water dynamics with GPR under a wide range of different conditions. Here, we assess in particular (i) the feasibility of monitoring the dynamic shape of the capillary fringe reflection and (ii) the relative precision of monitoring soil water dynamics averaged over the whole vertical extent by evaluating the bottom reflection. The phenomenology of the GPR response of a dynamically changing capillary fringe is developed from a soil physical point of view. We then explain experimentally observed phenomena based on numerical simulations of both the water content dynamics and the expected GPR response.

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Detecting infiltrated water and preferential flow pathways through time-lapse ground-penetrating radar surveys

The Science of The Total Environment ◽

10.1016/j.scitotenv.2020.138511 ◽

2020 ◽

Vol 726 ◽

pp. 138511 ◽

Cited By ~ 3

Author(s):

Simone Di Prima ◽

Thierry Winiarski ◽

Rafael Angulo-Jaramillo ◽

Ryan D. Stewart ◽

Mirko Castellini ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Preferential Flow ◽

Time Lapse ◽

Flow Pathways ◽

Preferential Flow Pathways ◽

Ground Penetrating

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Ground-penetrating radar surveys for the detection of preferential flow into soils

10.5194/egusphere-egu2020-4177 ◽

2020 ◽

Cited By ~ 1

Author(s):

Simone Di Prima ◽

Thierry Winiarski ◽

Rafael Angulo-Jaramillo ◽

Ryan D. Stewart ◽

Mirko Castellini ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Preferential Flow ◽

Three Dimensional ◽

Time Lapse ◽

Water Infiltration ◽

Single Ring ◽

Before And After ◽

Infiltration Tests ◽

Ground Penetrating ◽

Preferential Flows

<p>Preferential flow is more the rule than the exception, in particular during water infiltration experiments. In this study, we demonstrate the potential of GPR monitoring to detect preferential flows during water infiltration. We monitored time-lapse ground penetrating radar (GPR) surveys in the vicinity of single-ring infiltration experiments and created a three-dimensional (3D) representation of infiltrated water below the devices. For that purpose, radargrams were constructed from GPR transects conducted over two grids (1 m &#215; 1 m) before and after the infiltration tests. The obtained signal was represented in 3D and a threshold was chosen to part the domain into wetted and non-wetted zones, allowing the determination of the infiltration bulb. That methodology was used to detect the infiltration below the devices and clearly pointed at nonuniform flows in correspondence with the heterogeneous soil structures. The protocol presented in this study represents a practical and valuable tool for detecting preferential flows at the scale of a single ring infiltration experiment.</p>

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Estimating infiltration front depth using time-lapse multioffset gathers obtained from ground-penetrating-radar antenna array

Geophysics ◽

10.1190/geo2020-0590.1 ◽

2021 ◽

pp. 1-37

Author(s):

Hirotaka Saito ◽

Seiichiro Kuroda ◽

Toshiki Iwasaki ◽

Jacopo Sala ◽

Haruyuki Fujimaki

Keyword(s):

Antenna Array ◽

Ground Penetrating Radar ◽

Sand Dunes ◽

Time Lapse ◽

Sudden Increase ◽

Wetting Front ◽

Moisture Sensor ◽

Wave Velocities ◽

Ground Penetrating ◽

Infiltration Experiment

Non-destructive and non-invasive visualization and quantification of dynamic subsurface hydrological processes are needed. Using a ground penetrating radar (GPR) antenna array, time-lapse common-offset gather (COG) and common mid-point (CMP) data can be collected by fixing the antenna at a given location when scanning subsurface. This study aims to determine wetting front depths continuously during a field infiltration experiment by estimating electromagnetic (EM) wave velocities at given elapsed times using ground penetrating radar (GPR) antenna array data. A surface GPR antenna array system, consisting of 10 transmitters (Tx) and 11 receivers (Rx), that can scan each Tx-Rx combination in 10 s at a millisecond scale was used to acquire all 110 Rx-Tx combinations in approximately 1.5 s. The field infiltration experiment was conducted at an experimental field near the Tottori Sand Dunes in Japan. Using the estimated EM wave velocity from the CMP data, the depth to the wetting front was computed every minute. The estimated wetting front arrival time agreed with the time at which a sudden increase in the moisture sensor output was observed at a depth from 20 cm and below. This study demonstrated that time-lapsed CMP data collected with the GPR antenna array system could be used to estimate EM wave velocities continuously during the infiltration. The GPR antenna array was capable of accurate and quantitative tracking of the wetting front.

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Multi-offset ground-penetrating radar imaging of a lab-scale infiltration test

Hydrology and Earth System Sciences ◽

10.5194/hess-16-4009-2012 ◽

2012 ◽

Vol 16 (11) ◽

pp. 4009-4022 ◽

Cited By ~ 26

Author(s):

A. R. Mangel ◽

S. M. J. Moysey ◽

J. C. Ryan ◽

J. A. Tarbutton

Keyword(s):

Water Content ◽

Ground Penetrating Radar ◽

Time Lapse ◽

Volumetric Water Content ◽

Data Cube ◽

Sand Layer ◽

Wetting Front ◽

One Dimensional ◽

Ground Penetrating ◽

Infiltration Experiment

Abstract. A lab scale infiltration experiment was conducted in a sand tank to evaluate the use of time-lapse multi-offset ground-penetrating radar (GPR) data for monitoring dynamic hydrologic events in the vadose zone. Sets of 21 GPR traces at offsets between 0.44–0.9 m were recorded every 30 s during a 3 h infiltration experiment to produce a data cube that can be viewed as multi-offset gathers at unique times or common offset images, tracking changes in arrivals through time. Specifically, we investigated whether this data can be used to estimate changes in average soil water content during wetting and drying and to track the migration of the wetting front during an infiltration event. For the first problem we found that normal-moveout (NMO) analysis of the GPR reflection from the bottom of the sand layer provided water content estimates ranging between 0.10–0.30 volumetric water content, which underestimated the value determined by depth averaging a vertical array of six moisture probes by 0.03–0.05 volumetric water content. Relative errors in the estimated depth to the bottom of the 0.6 m thick sand layer were typically on the order of 2%, though increased as high as 25% as the wetting front approached the bottom of the tank. NMO analysis of the wetting front reflection during the infiltration event generally underestimated the depth of the front with discrepancies between GPR and moisture probe estimates approaching 0.15 m. The analysis also resulted in underestimates of water content in the wetted zone on the order of 0.06 volumetric water content and a wetting front velocity equal to about half the rate inferred from the probe measurements. In a parallel modeling effort we found that HYDRUS-1D also underestimates the observed average tank water content determined from the probes by approximately 0.01–0.03 volumetric water content, despite the fact that the model was calibrated to the probe data. This error suggests that the assumed conceptual model of laterally uniform, one-dimensional vertical flow in a homogenous material may not be fully appropriate for the experiment. Full-waveform modeling and subsequent NMO analysis of the simulated GPR response resulted in water content errors on the order of 0.01–0.03 volumetric water content, which are roughly 30–50% of the discrepancy between GPR and probe results observed in the experiment. The model shows that interference between wave arrivals affects data interpretation and the estimation of traveltimes. This is an important source of error in the NMO analysis, but it does not fully account for the discrepancies between GPR and the moisture probes observed in the experiment. The remaining discrepancy may be related to conceptual errors underlying the GPR analysis, such as the assumption of uniform one-dimensional flow, a lack of a sharply defined wetting front in the experiment, and errors in the petrophysical model used to convert dielectric constant to water content.

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Time Lapse Characterization of Leachate Flow Using Electromagnetics and Ground Penetrating Radar

10.1190/nsapc2015-056 ◽

2015 ◽

Author(s):

Matthew James ◽

David C. Nobes*

Keyword(s):

Ground Penetrating Radar ◽

Time Lapse ◽

Ground Penetrating

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Planform and stratigraphic signature of proximal braided streams: remote-sensing and ground-penetrating-radar analysis of the Kicking Horse River, Canadian Rocky Mountains

Journal of Sedimentary Research ◽

10.2110/jsr.2020.6 ◽

2020 ◽

Vol 90 (1) ◽

pp. 131-149

Author(s):

Natasha N. Cyples ◽

Alessandro Ielpi ◽

Randy W. Dirszowsky

Keyword(s):

Remote Sensing ◽

Ground Penetrating Radar ◽

Three Dimensional ◽

Time Lapse ◽

Braided Rivers ◽

Continental Divide ◽

Channel Belt ◽

Braided Streams ◽

And Migration ◽

Ground Penetrating

ABSTRACT Braided rivers have accumulated a dominant fraction of the terrestrial sedimentary record, and yet their morphodynamics in proximal intermountain reaches are still not fully documented—a shortcoming that hampers a full understanding of sediment fluxes and stratigraphic preservation in proximal-basin tracts. Located in the eastern Canadian Cordillera near the continental divide, the Kicking Horse River is an iconic stream that has served as a model for proximal-braided rivers since the 1970s. Legacy work on the river was based solely on ground observations of small, in-channel bars; here we integrate field data at the scale of individual bars to the entire channel belt with time-lapse remote sensing and ground-penetrating-radar (GPR) imaging, in order to produce a more sophisticated morphodynamic model for the river. Cyclical discharge fluctuations related to both diurnal and seasonal variations in melt-water influx control the planform evolution and corresponding stratigraphic signature of trunk channels, intermittently active anabranch channels, and both bank-attached and mid-channel bars. Three-dimensional GPR fence diagrams of compound-bar complexes are built based on the identification of distinct radar facies related to: i) accretion and migration of unit bars, ii) both downstream and lateral outbuilding of bar-slip foresets; iii) buildup of bedload sheets, iv) channel avulsion, and v) accretion of mounded bars around logs or outsized clasts. Trends observed downstream-ward include decreases in gradient and grain size decreases, trunk-channel shrinkage, intensified avulsion (with increase in abundance for anabranch channels), and a shift from high-relief to low-relief bar topography. The integration of ground sedimentology, time-lapse remote sensing, and GPR imaging demonstrates that proximal-braided streams such as the Kicking Horse River can be critically compared to larger systems located farther away from their source uplands despite obvious scale differences.

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Time-lapse ground penetrating radar difference reflection imaging of saline tracer flow in fractured rock

Geophysics ◽

10.1190/geo2019-0481.1 ◽

2020 ◽

Vol 85 (3) ◽

pp. H25-H37 ◽

Cited By ~ 2

Author(s):

Peter-Lasse Giertzuch ◽

Joseph Doetsch ◽

Mohammadreza Jalali ◽

Alexis Shakas ◽

Cédric Schmelzbach ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Fractured Rock ◽

Sampling Rate ◽

Time Lapse ◽

Transport Processes ◽

Local Data ◽

Tracer Injection ◽

Flow Through ◽

Reflection Imaging ◽

Ground Penetrating

The characterization of flow and transport processes in fractured rock is challenging because they cannot be observed directly and hydrologic tests can only provide sparse and local data. Time-lapse ground penetrating radar (GPR) can be a valuable tool to monitor such processes in the subsurface, but it requires highly reproducible data. As part of a tracer injection experiment at the Grimsel Test Site (GTS) in Switzerland, borehole reflection GPR data were acquired in a time-lapse survey to monitor saline tracer flow through a fracture network in crystalline rock. Because the reflections from the tracer in the sub-mm fractures appear extremely weak, a differencing approach has been necessary to identify the tracer signal. Furthermore, several processing steps and corrections had to be applied to meet the reproducibility requirements. These steps include (1) single-trace preprocessing, (2) temporal trace alignment, (3) correction of sampling rate fluctuations, (4) spatial trace alignment, (5) spike removal, and (6) postprocessing procedures applied to the difference images. This allowed successful tracer propagation monitoring with a clear signal that revealed two separate tracer flow paths. The GPR results are confirmed by conductivity meters that were placed in boreholes in the GTS. If sufficient data processing is applied, GPR is shown to be capable of resolving tracer flow through sub-mm aperture fractures by difference reflection imaging even in challenging surroundings where many reflectors are present.

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Ground-penetrating-radar response to fracture-fluid salinity: Why lower frequencies are favorable for resolving salinity changes

Geophysics ◽

10.1190/1.2957893 ◽

2008 ◽

Vol 73 (5) ◽

pp. J25-J30 ◽

Cited By ~ 42

Author(s):

Georgios P. Tsoflias ◽

Matthew W. Becker

Keyword(s):

Electrical Conductivity ◽

Ground Penetrating Radar ◽

Field Experiments ◽

Fractured Rock ◽

Low Frequency ◽

Signal Amplitude ◽

Time Lapse ◽

Fracture Aperture ◽

Fracture Fluid ◽

Ground Penetrating

Time-lapse ground-penetrating-radar (GPR) surveys exploit signal-amplitude changes to monitor saline tracers in fractures and to identify groundwater flow paths. However, the relationships between GPR signal amplitude, phase, and frequency with fracture aperture and fluid electrical conductivity are not well understood. We used analytical modeling, numerical simulations, and field experiments of multifrequency GPR to investigate these relationships for a millimeter-scale-aperture fracture saturated with water of varying salinity. We found that the response of lower-frequency radar signals detects changes in fluid salinity better than the response of higher-frequency signals. Increasing fluid electrical conductivity decreases low-frequency GPR signal wavelength, which improves its thin-layer resolution capability. We concluded that lower signal frequencies, such as [Formula: see text], and saline tracers of up to [Formula: see text] conductivity are preferable when using GPR to monitor flow in fractured rock. Furthermore, we found that GPR amplitude and phase responses are detectable in the field and predictable by EM theory and modeling; therefore, they can be related to fracture aperture and fluid salinity for hydrologic investigations of fractured-rock flow and transport properties.

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A geophysical investigation of the active Hockley Fault System near Houston, Texas

Geophysics ◽

10.1190/geo2012-0258.1 ◽

2013 ◽

Vol 78 (4) ◽

pp. B177-B185 ◽

Cited By ~ 10

Author(s):

Shuhab D. Khan ◽

Robert R. Stewart ◽

Maisam Otoum ◽

Li Chang

Keyword(s):

Ground Penetrating Radar ◽

Fault Location ◽

Gravity Data ◽

Time Lapse ◽

Radar Data ◽

Airborne Lidar ◽

Fault System ◽

Geophysical Investigation ◽

Geophysical Surveys ◽

Ground Penetrating

Sedimentation and deformation toward the Gulf of Mexico Basin cause faulting in the coastal regions. In particular, many active (but non-seismic) faults underlie the Houston metropolitan area. Using geophysical data, we have examined the Hockley Fault System in northwest Harris County. Airborne LiDAR is an effective tool to identify fault scarps and we have used it to identify several new faults and assemble an updated map for the faults in Houston and surrounding areas. Two different LiDAR data sets (from 2001 to 2008) provide time-lapse images and suggest elevation changes across the Hockley Fault System at the rate of 10.9 mm/yr. This rate is further supported by GPS data from a station located on the downthrown side of the Hockley Fault System indicating movement at 13.8 mm/yr. To help illuminate the subsurface character of the faults, we undertook geophysical surveys (ground-penetrating radar, seismic reflection, and gravity) across two strands of the Hockley Fault System. Ground-penetrating radar data show discontinuous events to a depth of 10 m at the main fault location. Seismic data, from a vibroseis survey along a 1-km line perpendicular to the fault strike, indicate faulting to at least 300-m depth. The faults have a dip of about 70°. Gravity data show distinct changes across the fault. However, there are two contrasting Bouguer anomalies depending on the location of the transects and their underlying geology. Our geophysical surveys were challenged by urban features (especially traffic and access). However, the survey results consistently locate the fault and hold significant potential to understand its deformational features as well as assist in associated building zoning.

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