scholarly journals Use of Ground Penetrating Radar, Hydrogeochemical Testing, and Aquifer Characterization to Establish Shallow Groundwater Supply to the Rehabilitated Ni-les’tun Unit Floodplain: Bandon Marsh, Coquille Estuary, Oregon, USA

2020 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
Curt D. Peterson ◽  
Harry M. Jol ◽  
David Percy ◽  
Robert Perkins
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Ground Penetrating Radar ◽  
Capillary Rise ◽  
Shallow Groundwater ◽  
Shallow Aquifer ◽  
Salinity Intrusion ◽  
Channel Network ◽  
Groundwater Supply ◽  
Ground Penetrating

Fluvial-tidal wetlands in the Ni-les’tun Unit (~200 hectares) of the Bandon Marsh, Coquille Estuary, Oregon, were analyzed for shallow aquifer conditions that could influence surface water-qualities in reconstructed marsh, pond, and discharge/tidal channels. The wetlands were surveyed for pre-historic channel features, depth to groundwater surface (GWS), and subsurface salinity intrusion by ground penetrating radar (GPR) in 50 profiles, totaling 11.1 km in track line distance. Only small flood-discharge/tidal channel features (<10 m width and 1–2 m depth) were recorded in the interior floodplain areas. GWS reflections were observed at 0.5–2.0 depth, where the GPR signal was not obscured by localized salinity intrusion (~0.5 km landward distance) from the adjacent Coquille Estuary channel. Top-sealed piezometers (1.5–2.0 m depth) were installed at 10 sites, where in-situ groundwaters were monitored for temperature (8.5–16.5° C), conductivity (<100–18,800 μS cm-1), and pH (2.5–7.8) on a seasonal basis. Dissolved oxygen was semi-quantitatively measured (ChemSticks) at some sites, and all sites were monitored (fall, winter, summer) for GWS level. Low dissolved oxygen (DO <1 ppm) at four sites was of particular concern for potential discharge into small channels that were to be constructed for juvenile salmonid nursery habitat. The horizontal and vertical asymmetries of conductivity (salinity), used as a conservative groundwater source tracer, and measured GWS elevation trends (gradients) led to a four-part flow model for shallow groundwater supply in the Ni-les’tun floodplain. Freshwater supplied, in part, by hillslope discharge contributes to low pH and low DO water quality in the shallow aquifer. Saline water, supplied by subsurface salinity intrusion and evaporative capillary rise, could introduce salinity toxicity to isolated (stagnant) surface ponds. Following construction of a dense channel network (2009–2011) by the Bandon Marsh National Wildlife Refuge, selected Ni-les’tun channel waters (13 sites) were monitored (2011-2012) for resulting water-quality. The tidally-connected channels generally showed improved water-quality relative to groundwater in some nearby piezometer sites. However, low-quality groundwater supply compromised some channel reaches (DO ~2.0–4.7 ppm) that depended on groundwater recharge from hillslope discharge during either summer or winter conditions.

Joint full-waveform GPR and ER inversion applied to field data acquired on the surface

Geophysics ◽  
2021 ◽  
pp. 1-77
Author(s):  
diego domenzain ◽  
John Bradford ◽  
Jodi Mead
Keyword(s):  
Ground Penetrating Radar ◽  
Joint Inversion ◽  
Waveform Inversion ◽  
Shallow Groundwater ◽  
Computational Domain ◽  
Alluvial Deposits ◽  
Subsurface Structures ◽  
Full Waveform ◽  
Stable Source ◽  
Ground Penetrating

We exploit the different but complementary data sensitivities of ground penetrating radar (GPR) and electrical resistivity (ER) by applying a multi-physics, multi-parameter, simultaneous 2.5D joint inversion without invoking petrophysical relationships. Our method joins full-waveform inversion (FWI) GPR with adjoint derived ER sensitivities on the same computational domain. We incorporate a stable source estimation routine into the FWI-GPR.We apply our method in a controlled alluvial aquifer using only surface acquired data. The site exhibits a shallow groundwater boundary and unconsolidated heterogeneous alluvial deposits. We compare our recovered parameters to individual FWI-GPR and ER results, and to log measurements of capacitive conductivity and neutron-derived porosity. Our joint inversion provides a more representative depiction of subsurface structures because it incorporates multiple intrinsic parameters, and it is therefore superior to an interpretation based on log data, FWI-GPR, or ER alone.

Seismic reflection and ground‐penetrating radar imaging of a shallow aquifer

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1310-1317 ◽  
Author(s):  
Steven J. Cardimona ◽  
William P. Clement ◽  
Katharine Kadinsky‐Cade
Keyword(s):  
Water Table ◽  
Ground Penetrating Radar ◽  
Low Frequency ◽  
Shallow Aquifer ◽  
Cone Penetrometer ◽  
Gradual Change ◽  
Cone Penetration ◽  
Geotechnical Data ◽  
Radar Images ◽  
Ground Penetrating

In 1995 and 1996, researchers associated with the US Air Force’s Phillips and Armstrong Laboratories took part in an extensive geophysical site characterization of the Groundwater Remediation Field Laboratory located at Dover Air Force Base, Dover, Delaware. This field experiment offered an opportunity to compare shallow‐reflection profiling using seismic compressional sources and low‐frequency ground‐penetrating radar to image a shallow, unconfined aquifer. The main target within the aquifer was the sand‐clay interface defining the top of the underlying aquitard at 10 to 14 m depth. Although the water table in a well near the site was 8 m deep, cone penetration geotechnical data taken across the field do not reveal a distinct water table. Instead, cone penetration tests show a gradual change in electrical properties that we interpret as a thick zone of partial saturation. Comparing the seismic and radar data and using the geotechnical data as ground truth, we have associated the deepest coherent event in both reflection data sets with the sand‐clay aquitard boundary. Cone penetrometer data show the presence of a thin lens of clays and silts at about 4 m depth in the north part of the field. This shallow clay is not imaged clearly in the low‐frequency radar profiles. However, the seismic data do image the clay lens. Cone penetrometer data detail a clear change in the soil classification related to the underlying clay aquitard at the same position where the nonintrusive geophysical measurements show a change in image character. Corresponding features in the seismic and radar images are similar along profiles from common survey lines, and results of joint interpretation are consistent with information from geotechnical data across the site.

scholarly journals Ground-penetrating radar insight into a coastal aquifer: the freshwater lens of Borkum Island

2013 ◽  
Vol 17 (2) ◽  
pp. 519-531 ◽  
Author(s):  
J. Igel ◽  
T. Günther ◽  
M. Kuntzer
Keyword(s):  
Sea Level ◽  
Ground Penetrating Radar ◽  
Capillary Rise ◽  
Groundwater Table ◽  
Distributed Monitoring ◽  
Large Area ◽  
Hydraulic Simulation ◽  
Monitoring Wells ◽  
Ground Penetrating ◽  
Insight Into

Abstract. Freshwater lenses, as important resource for drinking water, are sensitive to climate changes and sea level rise. To simulate this impact on the groundwater systems, hydraulic subsurface models have to be designed. Geophysical techniques can provide information for generating realistic models. The aim of our work is to show how ground-penetrating radar (GPR) investigations can contribute to such hydrological simulations. In the pilot area, Borkum island, GPR was used to map the shape of the groundwater table (GWT) and to characterise the aquifer. In total, 20 km of constant offset (CO) profiles were measured with centre frequencies of 80 and 200 MHz. Wave velocities were determined by common midpoint (CMP) measurements and vertical radar profiling (VRP) in a monitoring well. The 80 MHz CO data show a clear reflection at the groundwater table, whereas the reflection is weaker for the 200 MHz data. After correcting the GPR water tables for the capillary rise, they are in good accordance with the pressure heads of the observation wells in the area. In the centre of the island, the groundwater table is found up to 3.5 m above sea level, however it is lower towards the coastline and marshland. Some local depressions are observed in the region of dune valleys and around pumping stations of the local water supplier. GPR also reveals details within the sediments and highly-permeable aeolian sands can be distinguished from less-permeable marine sediments. Further, a silt loam layer below the water table could be mapped on a large area. The reflection characteristics indicates scattered erosion channels in this layer that cause it to be an aquitard with some leakage. GPR provides a high resolution map of the groundwater table and insight into the stratigraphy of the sediments and their hydraulic properties. This is valuable complementary information to the observation of sparsely distributed monitoring wells as input to hydraulic simulation.

scholarly journals River sedimentation modeling using ground-penetrating radar

2021 ◽  
Vol 873 (1) ◽  
pp. 012041
Author(s):  
M A Firdaus ◽  
Widodo ◽  
Fatkhan
Keyword(s):  
Water Quality ◽  
Ground Penetrating Radar ◽  
Rapid Decline ◽  
Subsurface Imaging ◽  
Geophysical Method ◽  
Geological Models ◽  
Different Depths ◽  
Set Up ◽  
Ground Penetrating ◽  
Synthetic Models

Abstract In recent years, siltation has become quite a problem. It has been the main cause of flooding and a rapid decline in water quality. It is usually caused by a high river sedimentation rate and/or uncontrolled waste disposal. The increased rate of erosion also means that river sedimentation occurs faster than normal and could lead to environmental hazards, wildlife deaths, and the disruption of food and drinking water supply among other things. The question is how to monitor the sedimentation process of rivers without damaging the river itself. The suitable geophysical method is GPR. GPR is an active, non-intrusive geophysical method in which electromagnetic radiation and the reflected signals in the form of radar pulses are used for subsurface imaging. The objective is to investigate river sedimentation using GPR, we created the synthetic models based on geological models of rivers with different depths to create their 2-D radargrams to predict the actual model. We set up the first model RSM-I as control which consists of a layer of freshwater with ρ = 16 Ωm, k = 81 and μ r = 1 of depth 5 m, two layers of sandstone with ρ = 850 Ωm, k = 2.5 and μ r = 1 of total depth 4 m, and a layer of claystone with ρ = 120 Ωm, k = 11 and μ r = 1 of depth 1 m. RSM-II and III are added with a buildup of saturated sediment with ρ = 30 Ωm, k = 15, and μ r = 1 of depth 2.5 and 4 m, respectively. The radargrams’ reflector for each model shows a two-way travel time of 300-350, 150-200, and 60-90 ns in their respective order. GPR models can differentiate between the saturated sediment and freshwater, it shows good results regarding sediment investigation in rivers.

scholarly journals Avaliação da qualidade da água em aquífero raso em Campos dos Goytacazes, Rio de Janeiro, Brasil

2021 ◽  
Vol 14 (6) ◽  
pp. 3241
Author(s):  
Cleber De Jesus Santos ◽  
Luca Lämmle ◽  
Vinicius Borges Moreira ◽  
Jefferson De Lima Picanço ◽  
Ronaldo Luiz Mincato ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Water Quality ◽  
Water Resources ◽  
Urban Areas ◽  
Rio De Janeiro ◽  
Shallow Groundwater ◽  
Field Work ◽  
Shallow Aquifer ◽  
Groundwater Levels ◽  
E Coli

Diversas formas de uso e ocupação em áreas urbanas tem ocasionado impactos ambientais negativos em diferentes escalas, sendo um deles a degradação dos recursos hídricos, que tem suscitado novas discussões sobre mecanismos de alteração da água subterrânea rasa. A proposição de estratégias metodológicas eficientes a partir da identificação e dimensionamento de características hidroquímicas da água em determinado espaço geográfico, consiste em desafio oportuno a colaborar para a conservação e uso adequado. Diante desse contexto, o objetivo do trabalho é analisar a qualidade da água no aquífero raso em área urbana Campos dos Goytacazes/RJ, correlacionando com a influência de estruturas urbanas nessa dinâmica. Foram coletadas e analisadas amostras de água de 15 poços, além de dados potenciométricos, a fim de correlacionar fatores como: qualidade da água, tipo de uso por parte da população, influência do cemitério, e hidrodinâmica subsuperficial. Tais poços foram previamente espacializados, seguido da coleta e armazenamento das amostras, análise em laboratório, e interpretação a partir das diferentes variáveis que compuseram o quadro síntese para análise simplificada. Em adição, foi elaborado mapa potenciométrico a partir dos níveis freáticos encontrados, permitindo compilar os parâmetros elencados. Os resultados sugerem que o lençol freático é consideravelmente raso na área estudada, tornando os recursos hídricos mais vulneráveis. Por se tratar de uma área de múltiplos usos, como residencial, agrícola, comercial, além da presença de um cemitério, acaba por expor a região a maiores riscos de contaminação. Destaca-se que, conforme verificado em trabalho de campo, a região possui potenciais agentes poluidores, levando a um maior número de substâncias contaminantes que podem ser liberadas neste ambiente. Adicionalmente, constatou-se alteração dos padrões biológicos, físicos e químicos, com contaminações acima do valor máximo permitido em lei para os seguintes elementos: Fe, Al, Pb, Mn e P, além da presença de Escherichia coli (E. Coli).       Assessment of water quality in a shallow aquifer in Campos dos Goytacazes, Rio de Janeiro, Brazil A B S T R A C TVarious forms of use and occupation in urban areas have caused negative environmental impacts at different scales, one of them being the degradation of water resources, which has given rise to new discussions on mechanisms for altering shallow groundwater. The proposition of efficient methodological strategies based on the identification and dimensioning of the hydrochemical characteristics of water in a given geographic space is an opportune challenge to collaborate for the conservation and proper use. In this context, the objective of this work is to analyze the water quality in the shallow aquifer in urban area Campos dos Goytacazes/RJ, correlating with the influence of urban structures in this dynamic. Water from 15 wells were collected and analyzed, in addition to potentiometric data, in order to correlate factors such as: water quality, type of use by the population, influence of the cemetery, and subsurface hydrodynamics. Such wells were previously spatialized, followed by collection and storage of aggregates, laboratory analysis, and interpretation based on the different variables that made up the synthetic framework for simplified analysis. In addition, a potentiometric map was drawn up from the groundwater levels found, allowing for the compilation of the listed parameters. The results obtained that the water table is considerably shallow in the studied area, making water resources more vulnerable. As it is an area with multiple uses, such as residential, agricultural, commercial, in addition to the presence of a cemetery, it ends up exposing the region to greater risks of contamination. It is noteworthy that, as verified in field work, the region has potential polluting agents, leading to a greater number of contaminants that can be released into this environment. Additionally, there was a change in biological, physical and chemical standards, with contamination above the maximum value allowed by law for the following elements: Fe, Al, Pb, Mn and P, in addition to the presence of Escherichia coli (E. Coli).Keywords: Hydrochemistry; Hydrodynamic; Shallow Aquifer; Contamination.

scholarly journals Ground Penetrating Radar Attenuation Expressions in Shallow Groundwater Research

2020 ◽  
Vol 25 (1) ◽  
pp. 153-160
Author(s):  
Maria Catarina Paz ◽  
Francisco J. Alcalá ◽  
Luís Ribeiro
Keyword(s):  
Ground Penetrating Radar ◽  
Heterogeneous Media ◽  
Wave Attenuation ◽  
Shallow Groundwater ◽  
Low Loss ◽  
Database Analysis ◽  
Physically Based ◽  
The Status ◽  
Ground Penetrating ◽  
Effective Penetration

The electromagnetic-wave attenuation coefficient determines the overall resolution and effective penetration depth of ground penetrating radar (GPR) surveys. Despite this relevance to the design of proper GPR surveys, the attenuation expressions are rarely used in the applied shallow groundwater research (SGR) literature. This work examines the status of the attenuation expressions in SGR. For this, 73 GPR case studies (in 47 papers), including some information concerning the attenuation variables and parameters, were selected to build a database. From these, 18 cases (in 10 papers) provided attenuation expressions and only 11 cases (in 4 papers) used those expressions. Two types of expressions were identified, physically based global ones that try to solve a broad (but not complete) range of environmental and field technical conditions, and non-global ones adapted for specific geological environments and resolution needed. The database analysis showed that both global and non-global expressions were used exclusively in low-loss media to report an attenuation range of 0.1–21.5 dB m −1 by using common antenna frequencies in the 25–900 MHz range. The range of the attenuation expressions validity in SGR is biased because no surveys in variable-loss heterogeneous media and wider antenna frequency intervals could be compiled. The attenuation database generated seeks to improve the design of GPR surveys in SGR.

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

Deteksi Bentuk Objek Bawah Tanah Menggunakan Pengolahan Citra B-Scan pada Ground Penetrating Radar (GPR)

2017 ◽  
Vol 3 (1) ◽  
pp. 73-83
Author(s):  
Rahmayati Alindra ◽  
Heroe Wijanto ◽  
Koredianto Usman
Keyword(s):  
Signal Processing ◽  
Ground Penetrating Radar ◽  
Post Processing ◽  
Data Survey ◽  
Ground Penetrating

Ground Penetrating Radar (GPR) adalah salah satu jenis radar yang digunakan untuk menyelidiki kondisi di bawah permukaan tanah tanpa harus menggali dan merusak tanah. Sistem GPR terdiri atas pengirim (transmitter), yaitu antena yang terhubung ke generator sinyal dan bagian penerima (receiver), yaitu antena yang terhubung ke LNA dan ADC yang kemudian terhubung ke unit pengolahan data hasil survey serta display sebagai tampilan output-nya dan post  processing untuk alat bantu mendapatkan informasi mengenai suatu objek. GPR bekerja dengan cara memancarkan gelombang elektromagnetik ke dalam tanah dan menerima sinyal yang dipantulkan oleh objek-objek di bawah permukaan tanah. Sinyal yang diterima kemudian diolah pada bagian signal processing dengan tujuan untuk menghasilkan gambaran kondisi di bawah permukaan tanah yang dapat dengan mudah dibaca dan diinterpretasikan oleh user. Signal processing sendiri terdiri dari beberapa tahap yaitu A-Scan yang meliputi perbaikan sinyal dan pendektesian objek satu dimensi, B-Scan untuk pemrosesan data dua dimensi  dan C-Scan untuk pemrosesan data tiga dimensi. Metode yang digunakan pada pemrosesan B-Scan salah satunya adalah dengan  teknik pemrosesan citra. Dengan pemrosesan citra, data survey B-scan diolah untuk didapatkan informasi mengenai objek. Pada penelitian ini, diterapkan teori gradien garis pada pemrosesan citra B-scan untuk menentukan bentuk dua dimensi dari objek bawah tanah yaitu persegi, segitiga atau lingkaran. 

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