Hydrogeophysics

The study of groundwater potential in Wadi El-Assiuoti is of a prime importance for both current and future development. In this paper the groundwater occurrences are investigated using integrated; 1) geophysical well logging (Self potential, Resistivity and Gamma Ray), 2) subsurface lithologic data and 3) hydraulic data (trans-missivity, transmissibility, hydraulic conductivity and storativity) in addition to reviewing all studies on Wadi El-Assiuoti. Different petrophysical parameters (formation water resistivity, formation factor, porosity, perme-ability, salinity and shale volume) are computed. These parameters are very necessary to identify the aquifers characteristics in the surveyed area. The integration between geophysical and hydrogeological data shows the possibility of two water bearing formation (Quaternary and Plio-Pleistocene). Generally, porosity and perme-ability values of these aquifers decrease toward the west. The aquifers exist under unconfined to semi confined conditions. The wide range values of both well efficiency and hydraulic conductivity indicate heterogeneity in the lithology and hydraulic characteristics of the aquifer materials. The computed transmissibility values indicate that the water-bearing sediments in the area under investigation are generally of high productivity. In some localities due to the heterogeneity of sediment, the water-bearing sediments are of moderate productivity. Recently , due to the increase of drilling activities at the middle part of the studied area some problems concerning the groundwater potential and high salinity in the area are happening.

Ce travail concerne une étude géophysique de la nappe calcaire du Crétacé Supérieur de Sidi Ahmed (Béja, Nefza). Cette nappe est sous-exploitée (quelques forages) et peu développée (études fragmentaires). Cette étude a permit de cerner la structuration de la région au moyen des données gravimétriques avec l'individuation de l'extension et des directions des structures (anticlinal de J. Abiod de Nefza, anticlinal de Sidi Ahmed, synclinal perchée de Dhehirat). L'analyse gravimétrique a pu mettre aussi en évidence les accidents majeurs morcelant la zoned'étude en compartiments structuraux distincts. Les sondages électriques verticaux réalisés ont permis de tracer des pseudosections et des cartes d'isorésistivités individualisant la géométrie de l'aquifère calcaire du crétacé supérieur de Sidi Ahmed. La tomographie électrique quant à elle a fournit une image fine du dégré de fracturation et de karstification au niveau de quelques sites aux abords de l'anticlinal de Sidi Ahmed. Cette étude préliminaire a pu cerner la structuration de la région et le potentiel hydrogéologique de la nappe profonde calcaire de Sidi Ahmed, permettant de mieux guider de futures investigations.
Mots clés Mots clés : Aquifère, Sidi Ahmed, Nefza, Béja, Structuration, Failles, Hydrogéologie, Gravimétrie, Electrique.

The time domain electromagnetic method (TDEM) is applied to monitor, to delineate and to map the saltwater intrusion zones in
the Mediterranean Plio-Quaternary aquifer. Forty-two TDEM soundings were carried out in the coastal plain of Nabeul–
Hammamet region (NE Tunisia). TDEM resistivity data were correlated with the existing borehole logging data to assign them to
a particular lithology and to provide information about the position of the freshwater–seawater transition zone. The geoelectric
sections showing the vertical configuration of seawater intrusion, with the brackish-salty-saturated zones, have a resistivity
ranging from ~0.1 to 5 Ω
m and are detected at a depth lower than 1.5 m. The salinized zones are located at Nabeul (Sidi Moussa,
Sidi El Mahrsi, Al Gasba and Mrazgua) and at Hammamet (Touristic zone of Hammamet north and south, Baraket Essahel) and
reached a distance of 4 km from the coastline, indicating a severe state for the aquifer in these zones. These TDEM results are
confirmed by the increase of chloride concentration content in the analysed water samples of monitoring wells. Moreover, in the
northeastern part, the presence of a saltwater front located far from the coast and along the NW–SE major surface fault can be
explained by two hypothesis: (i) this fault seems to provide a conduit for seawater to move readily towards the water wells and
(ii) the clay and gypsum infiltration of marine Messinian deposits through the fault plane leads to low resistivities. Finally, it
comes out from this study that TDEM survey has successfully depicted salinized zones of this coastal aquifer. Copyright © 2012
John Wiley & Sons, Ltd.
KEY WORDS TDEM; saltwater intrusion; Plio-Quaternary aquifer; Nabeul–Hammamet; Tunisia

To understand the impact of sea level rise (SLR) and aquifer intensive use would cause to the groundwater level and saltwater intrusion, an integrated relationship between salinity and electrical resistivity of a Quaternary aquifer is established in the northern part of East Nile Delta (El Sharkia area), Egypt. Historical data of groundwater salinity are mapped and compared with the current water samples to better understand the salinity spatial variability. The salinity maps show that salinization has increased sustainably. Additionally, the transition/dynamic zone related to SLR and/or excessive pumping can be addressed. In particular, the surface DC resistivity soundings were carried out to demonstrate the vertical and horizontal salinity distributions in the area. In the course of this study, the 1D model generation using a hybrid genetic algorithm (GA) was applied and tested using borehole information. The constructed geoeletrical cross-sections emphasize and delineate the extension of saltwater intrusion. Cleary, it is found that due to excessive pumping from shallow wells over the last decades, the subsurface resistivity and TDS vertical distributions can change rapidly within a short distance. Additionally, the results show that despite the dominance of brackish and saltwater at the northern part of the area, perched low conductive lenses are observed reflecting a low level of groundwater salinization. To obtain a link between water salinity and aquifer resistivity, an empirical relationship was derived to predict the salinity variations at different depths. In comparison with the measured total dissolved solids (TDS), the predicted salinity map appears realistic. These results demonstrate the important role of the integration between resistivity and salinity measurements for mapping the groundwater salinization with depth, and call for further research to plan and manage the area's water resources.

Egypt is one of the most densely populated countries with an annual high birth rate. This Middle Eastern country depends on a main source of water, which is the running surface water represented mainly by the water of the Nile River which consider as a lifeline and depends on a secondary source that has become more important in recent years due to the increase in populations, urbanizations and land reclamation projects in Egypt, which is the groundwater. There is a huge reservoir of fresh underground water below the mud layer of the Nile Delta, known as the Nile Delta aquifer. However, this aquifer has been exposed not long ago to many factors led to the decline in its quality, and the major factor of these is the invasion of salt water to fresh water within the aquifer. The saltwater had intruded from the northern and eastern parts of Egypt along the Mediterranean Sea and Suez Canal, respectively. It can also be noticed that a large part of agricultural areas in the northern parts has been affected by this intrusion. This invasion occurs because of the humans who caused the phenomenon of global warming, which led to the rise of sea level and caused the invasion of high denser salt water into the aquifer. The increase in the rate of pumping in the areas near sources of salt water above the normal rate accelerates this harmful invasion and causes vertical upwelling of saltwater from deeper parts causing degradation to groundwater quality. Accordingly, groundwater assessment and management have become extremely important.
This research which based on other scientific works gives a brief description of the Nile delta aquifer and review previous studies on its groundwater and presents an overview of the seawater intrusion problem within it. The salinity of the water is an important parameter in groundwater evaluation research. All the studies showed that the concentration of saltwater had increased within the aquifer in the last decades and exceeded the World Health Organization standards for drinking water. Additionally, the transition/dynamic zone related to sea level rise and/or excessive pumping can be addressed. Those studies were conducted by using direct current resistivity technique to demonstrate the vertical and horizontal salinity distributions in the area and answer the critical key questions regarding the current and future management of the Nile Delta Aquifer.

This study is a trial to predict the relationship between
the formation resistivity data and some petrophysical
properties of rocks in Tut and Khalda oil fields at the northern
Western Desert, Egypt. First, the deep resistivity (deep
laterolog (LLD)) and gamma ray (GR) logs are smoothed by
a linear combination of simple fitting functions that satisfy the
smoothness criteria, and consequently the behavior of both
logs can be simulated. Next, the smoothed log data are divided
into branches, where high and frequent excursions in GR and
LLD logs occur. In subsequent steps, the Dar-Zarrouk parameters
are calculated and followed by a smoothing process for
each branch. Based on a visual inspection of these parameters
with effective porosity logs, the Dar-Zarrouk parameters are
divided into zones and then interpreted in terms of shale content
and the potentiality of the two oil fields. The permeability
trend observed in core samples showed that the calculated
parameters provide an adequate qualitative prediction for the
petrophysical properties including the overall permeability
trends. Despite the fact that the predicted permeability trends
in Khalda oil field coincides with those measured from core
samples, a weak correlation is observed, which can be attributed
to the reservoir heterogeneity with dominance of laminated
and dispersed shale and/or iron oxides. The potentiality
of the proposed method lies in its simplicity, requiring only
GR, LLD, and effective porosity logs. However, it would be
more meaningful if the above method is tested in areas with
diverse geological environment.

The antenna of a zero-offset off-ground groundpenetrating radar can be accurately modeled using a linear system of frequency-dependent complex scalar transfer functions under the assumption that the electric field measured by the antenna locally tends to a plane wave. First, we analyze to which extent this hypothesis holds as a function of the antenna height above a multilayered medium. Second, we compare different methods to estimate the antenna phase center, namely, 1) extrapolation of peak-to-peak reflection values in the time domain and 2) frequency-domain full-waveform inversion assuming both frequencyindependent and -dependent phase centers. For that purpose, we performed radar measurements at different heights above a perfect electrical conductor. Two different horn antennas operating, respectively, in the frequency ranges 0.2-2.0 and 0.8-2.6 GHz were used and compared. In the limits of the antenna geometry, we observed that antenna modeling results were not significantly affected by the position of the phase center. This implies that the transfer function model inherently accounts for the phase-center positions. The results also showed that the antenna transfer function model is valid only when the antenna is not too close to the reflector, namely, the threshold above which it holds corresponds to the antenna size. The effect of the frequency dependence of the phase-center position was further tested for a two-layered sandy soil subject to different water contents. The results showed that the proposed antenna model avoids the need for phase-center determination for proximal soil characterization.

The present study demonstrates the efficacy of electrical resistivity technique to understand the groundwater regime in coastal aquifers in parts of Sindhudurg district, Maharashtra. This helps to delineate the zones of seawater intrusion and its extent into fresh water aquifers and to locate fresh groundwater pockets to meet the water demand of society. The study area encompasses the western coastal area of Redi-Vengurla-Kudal-Malvan, Sindhudurg district, Maharashtra, bounded by coordinates Latitudes 15.7° to 16.15° and Longitudes 73.50° to 73.8°. The area comprise of laterites, basalts and coastal alluvium with varied physiographic conditions and several NE-SW, NW-SE to EW lineaments. Vengurla and Malvan areas are from coastal stretch with varied annual rainfall and physiographic conditions, whereas, Kudal is away from the coast. A total of 69 vertical electrical sounding (VES) points using Schlumberger configuration with a maximum electrode separation AB of 200 m is considered in this study. The apparent resistivity curves were generated and interpreted using IPI2WIN software, after marginally modifying the manually interpreted results, keeping in view the local geology and hydrogeology. The true resistivity sections of resistivity data were generated over four EW and four NS trending profiles. The top layer in the entire study area showed varying thickness in lateritic formation. A few coastal stations viz. 49, 54, 57, 64, 65 and 66 revealed saline water ingress into the fresh water zones and the effect spreads up to about 4 km inland in that area. The subsurface in the study region further suggests the flow of saline water from coastal side.

An integrated hydrogeophysical inversion approach was used to remotely infer the unsaturated soil hydraulic parameters from time-lapse ground-penetrating radar (GPR) data collected at a fixed location over a bare agricultural field. The GPR model combines a full-waveform solution of Maxwell’s equations for three-dimensional wave propagation in planar layered media together with global reflection and transmission functions to account for the antenna and its interactions with the medium. The hydrological simulator HYDRUS-1D was used with a two layer single- and dual-porosity model. The radar model was coupled to the hydrodynamic model, such that the soil electrical properties (permittivity and conductivity) that serve as input to the GPR model become a function of the hydrodynamic model output (water content), thereby permitting estimation of the soil hydraulic parameters from the GPR data in an inversion loop. To monitor the soil water content dynamics, time-lapse GPR and time domain reflectometry (TDR) measurements were performed, whereby only GPR data was used in the inversion. Significant effects of water dynamics were observed in the time-lapse GPR data and in particular precipitation and evaporation events were clearly visible. The dual porosity model provided better results compared to the single porosity model for describing the soil water dynamics, which is supported by field observations of macropores. Furthermore, the GPR-derived water content profiles reconstructed from the integrated hydrogeophysical inversion were in good agreement with TDR observations. These results suggest that the proposed method is promising for non-invasive characterization of the shallow subsurface hydraulic properties and monitoring water dynamics at the field scale.

In this paper an information management system used in Attica Greece that combines modeling with the integrated management of water, sewerage and storm water infrastructure is presented. From this information management system there are proposed certain public works that are grouped in two categories, i.e. works that are needed for the entire Attica district and have a general character for the whole region (1 st category works) and then, works that are specifically needed for every particular and individual municipality (2 nd category works).

We used integrated hydrogeophysical inversion of time-lapse, proximal ground penetrating radar (GPR) data to remotely infer the unsaturated soil hydraulic properties of a laboratory sand during an infiltration event. The inversion procedure involved full-waveform modeling of the radar signal and one-dimensional, vertical flow modeling. We combined the radar model with HYDRUS-1D. The radar system was set up using standard, handheld vector network analyzer technology. Significant effects of water dynamics were observed on the time-lapse radar data. The estimated hydraulic parameters were relatively consistent with direct characterization of undisturbed sand samples. Significant differences were particularly observed for the saturated hydraulic conductivity, which was underestimated by two orders of magnitude. Nevertheless, the use of soil hydraulic parameters derived from reference measurements failed to correctly predict water dynamics, whereas GPR-based predictions captured some of the major features of time domain reflectometry measurements and better agreed with visual observations. These results suggest that the proposed method is promising for noninvasive, effective hydraulic characterization of the shallow subsurface and hence, monitoring of water dynamics at the field scale.

Accurate estimates of surface soil moisture are essential in many research fields, including agriculture, hydrology, and meteorology. The objective of this study was to evaluate two remote-sensing methods for mapping the soil moisture of a bare soil, namely, L-band radiometry using brightness temperature and ground-penetrating radar (GPR) using surface reflection inversion. Invasive time-domain reflectometry (TDR) measurements were used as a reference. A field experiment was performed in which these three methods were used to map soil moisture after controlled heterogeneous irrigation that ensured a wide range of water content. The heterogeneous irrigation pattern was reasonably well reproduced by both remote-sensing techniques. However, significant differences in the absolute moisture values retrieved were observed. This discrepancy was attributed to different sensing depths and areas and different sensitivities to soil surface roughness. For GPR, the effect of roughness was excluded by operating at low frequencies (0.2-0.8 GHz) that were not sensitive to the field surface roughness. The root mean square (rms) error between soil moisture measured by GPR and TDR was 0.038 m 3 · m −3 . For the radiometer, the rms error decreased from 0.062 (horizontal polarization) and 0.054 (vertical polarization) to 0.020 m 3 · m −3 (both polarizations) after accounting for roughness using an empirical model that required calibration with reference TDR measurements. Monte Carlo simulations showed that around 20% of the reference data were required to obtain a good roughness calibration for the entire field. It was concluded that relatively accurate measurements were possible with both methods, although accounting for surface roughness was essential for radiometry.

This study aimed to identify potential subsurface water resources (underground river in Saleh Cave) on the Maros karst morphology. Identification of an underground river channel at Saleh Cave using resistivity measurements geoelectric method Wenner-Schlumberger configuration compiled with Saleh Cave dimensional mapping data, as well as muscular and topographical measurements. Geoelectric measurement consists of 9 tracks, acquired 2D and 3D resistivity cross-section shows the flow of the cave identified through the high resistivity range ρ> 2000 Ωm. Goa Saleh has a long corridor about 200m, where an underground river channel identified at a depth of 84-110 meters above sea level trending N320oE or leads from the Southeast to the Northwest. This is consist with the results of measurements of the fracture pattern (strike / dip) in the study site showing the same pattern of dominant fractures trending with underground streams in Saleh Cave. Compilation method used in this research can identify potential water resources that located beneath the surface karst morphology.
Keywords: Karst Maros morphology, Underground river, Geoelectricity, Saleh Cave

Accurate estimates of surface soil moisture are essential in many research fields, including agriculture, hydrology, and meteorology. The objective of this study was to evaluate two remote-sensing methods for mapping the soil moisture of a bare soil, namely, L-band radiometry using brightness temperature and ground-penetrating radar (GPR) using surface reflection inversion. Invasive time-domain reflectometry (TDR) measurements were used as a reference. A field experiment as performed in which these three methods were used to map soil moisture after controlled heterogeneous irrigation that ensured a wide range of water content. The heterogeneous irrigation pattern was reasonably well reproduced by both remote-sensing techniques. However, significant differences in the absolute moisture values retrieved were observed. This discrepancy was attributed to different sensing depths and areas and different sensitivities to soil surface roughness. For GPR, the effect of roughness was excluded by operating at low frequencies (0.2–0.8 GHz) that were not sensitive to the field surface roughness. The root mean square (rms) error between soil moisture measured by GPR and TDR was 0.038 m3 · m−3. For the radiometer, the rms error decreased from 0.062 (horizontal polarization) and 0.054 (vertical polarization) to 0.020 m3 · m−3 (both polarizations) after accounting for roughness using an empirical model that required calibration with reference TDR measurements. Monte Carlo simulations showed that around 20% of the reference data were required to obtain a good roughness calibration for the entire field. It was concluded that relatively accurate measurements were possible with both methods, although accounting for surface roughness was essential for radiometry.

Groundwater, traditionally extracted from hand-dug wells and boreholes is the main drinking water source in the Northern Region of Ghana. Many boreholes have been constructed in the region to increase accessibility to potable water mainly as part of rural water supply projects where borehole siting has to be relatively cheaper. These projects have resulted in low success rates of borehole drilling because of the application of inefficient and simple geophysical techniques supposed to be cheaper. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222 Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. The surveys were conducted at stations of existing dry and positive boreholes. Results show that the three geophysical techniques are efficient to identify groundwater accumulation zones. The ERI, EKS and 222 Rn are efficient to identify discontinuities, calculate hydraulic conductivity of discontinuities and identify areas of water circulation respectively. It is recommended that the ERI be used to obtain discontinuities and weak zones for drilling on rural water supply projects in the VB. The EKS and 222 Rn should be conducted to evaluate these features when high yield boreholes are required.

In this paper, we experimentally analyzed the feasibility of estimating soil hydraulic properties from 1.4 GHz radiometer and 0.8–2.6 GHz ground-penetrating radar (GPR) data. Radiometer and GPR measurements were performed above a sand box, which was subjected to a series of vertical water content profiles in hydrostatic equilibrium with a water table located at different depths. A coherent radiative transfer model was used to simulate brightness temperatures measured with the radiometer. GPR data were modeled using full-wave layered medium Green’s functions and an intrinsic antenna representation. These forward models were inverted to optimally match the corresponding passive and active microwave data. This allowed us to reconstruct the water content profiles, and thereby estimate the sand water retention curve described using the van Genuchten model. Uncertainty of the estimated hydraulic parameters was quantified using the Bayesian-based DREAM algorithm. For both radiometer and GPR methods, the results were in close agreement with in situ time-domain reflectometry (TDR) estimates. Compared with radiometer and TDR, much smaller confidence intervals were obtained for GPR, which was attributed to its relatively large bandwidth of operation, including frequencies smaller than 1.4 GHz. These results offer valuable insights into future potential and emerging challenges in the development of joint analyses of passive and active remote sensing data to retrieve effective soil hydraulic properties.

Water scarcity is one of the major concerns that people are facing worldwide. Although the liquid is absolutely abundant through the globe, its availability poses too much problems specifically to each region. Those problems can result in one or a combination of three basic situations: declining water (drought), overabundance of surface water (floods) or degradation of the quality of water (pollution). All these situations are reflected in the scarcity of good quality water. Arid regions are particularly concerned. In such areas where groundwater contained in aquifers is usually perceived as providence, any project of groundwater exploration and exploitation must be preceded by prior careful and meticulous investigation, in order to avoid early and premature drying. This investigation is likely to predict the future behaviour of aquifers and to improve the groundwater resources management. Beside fundamental properties as hydraulic conductivity, the present paper that addresses the water sector in the semi-arid region of northern Cameroon emphasizes the importance of porosity on aquifer productivity and consequently on the groundwater resources management. The porosity of the local aquifer has then been determined using the Waxman and Smits model which establishes a reliable relationship between the apparent and corrected formation factors, F a and F c , taking the clay effects into consideration. This approach can be applied in other similar semi-arid regions through the world.

In this study, two distinctive pollutants were identified and mapped around the dumpsites in Eneka Town, Obio/Akpo Local Government Area of Rivers State, Nigeria. These are zones of anomalously high resistivity, probably gases containing methane (CH4) since they rarely dissociate in water and may have come from the biodegradation of organic wastes or petroleum wastes and leachate plumes of low resistivity containing organic substances and dissolved solids. The study areas were delineated in both the 2-D and vertical electrical sounding sections respectively as anomalously high resistive zones. These were identified and mapped in the inverse model sections as reddish to purple zones of high resistivity between 618Ωm to 1713 Ωm between the depths 1.25m to 17.3m in the entire sections. The pollutants were continuous and displaced to various degrees on each of the inverse models. The concentration levels decrease as they were displaced eastward of the dumpsite. This is confirmed by the increase in the resistivity of these compounds; 1713 Ωm in profile line1 to 1915 Ωm in profile line 3. This may be probably due to dilution effect of the gases in other fluids as it moves away from the dumpsite. A contaminant leachate plume was delineated in both the 2-D resistivity imaging and the vertical electrical sounding sections as low resistivity zones. These were identified and mapped as low resistivity between 1.25m and 17.3m in the entire inverse model sections. The least resistivity zone occurred along profile line 1, while the highest occurred in profile line 3. This suggests that the concentration levels of ions in the leachate decreases away from the waste dumpsites.

The Quaternary aquifer of
Wadi Ham, UAE has been overexploited
during the last two decades
to meet the increasing water demands.
As a result, the dynamic
balance between freshwater and
seawater has been disturbed and the
quality of the groundwater has
deteriorated. In this paper, a 2D
earth resistivity survey was conducted
in Wadi Ham in the area
between Fujairah and Kalba to
delineate the seawater intrusion.
Existing monitoring wells were used
to measure the horizontal and vertical
variations in water salinity and
thus to improve the interpretation of
earth resistivity imaging data. Results
of vertical electrical soundings
and chemical analyses of collected
water samples were used to obtain
an empirical relationship between
the inferred earth resistivity and the
amount of total dissolved solids.
This relationship was used along
with the true resistivity sections
resulting from the inversion of 2D
resistivity data to identify three
zones of water-bearing formation
(fresh, brackish, and salt-water
zones). Along the four 2D resistivity
profiles, the depth to the freshbrackish
interface exceeded 50 m at
the western part of the area and was
in the order of 10 m or less in the
eastern side near the shoreline.
Depth to the brackish-saline water
interface reached about 70 m in the
western side and was in the order of
20 m in the eastern side. The thickness
of the fresh water zone decreases
considerably in the farming
areas toward Kalba and thus the
degree of seawater intrusion increases.

In this study, two distinctive pollutants were identified and mapped around the dumpsites in Eneka Town, Obio/Akpo Local Government Area of Rivers State, Nigeria. These are zones of anomalously high resistivity, probably gases containing methane (CH4) since they rarely dissociate in water and may have come from the biodegradation of organic wastes or petroleum wastes and leachate plumes of low resistivity containing organic substances and dissolved solids. The study areas were delineated in both the 2-D and vertical electrical sounding sections respectively as anomalously high resistive zones. These were identified and mapped in the inverse model sections as reddish to purple zones of high resistivity between 618Ωm to 1713 Ωm between the depths 1.25m to 17.3m in the entire sections. The pollutants were continuous and displaced to various degrees on each of the inverse models. The concentration levels decrease as they were displaced eastward of the dumpsite. This is confirmed by the increase in the resistivity of these compounds; 1713 Ωm in profile line1 to 1915 Ωm in profile line 3. This may be probably due to dilution effect of the gases in other fluids as it moves away from the dumpsite. A contaminant leachate plume was delineated in both the 2-D resistivity imaging and the vertical electrical sounding sections as low resistivity zones. These were identified and mapped as low resistivity between 1.25m and 17.3m in the entire inverse model sections. The least resistivity zone occurred along profile line 1, while the highest occurred in profile line 3. This suggests that the concentration levels of ions in the leachate decreases away from the waste dumpsites.

This study reports a result of the hydrogeophysical survey conducted in the site of Hamzakoy (Gelibolu Peninsula-Northwestern Turkey) by using direct current resistivity method. The aim of the study is to detect aquifer boundaries of Upper Pleistocene aged shallow marine carbonates of Dardanelles Group not outcropping in the site but exposing in the surrounding of it. The modeled geo-electrical section is also examined about why the aquifer consisting of the carbonate rock formation do not outcrop and is overlaid by clastic deposits in the survey site. This allows us further and detailed hydrogeophysical surveys to detect aquifer boundaries in a more extend than the site in the view of regional geology and tectonic activity. The site is situated in the northern part of the Gelibolu Peninsula. The peninsula is covered by the sedimentary sequence of Eocene-Oligocene aged and the unconformably overlaying sedimentary sequence of Upper Miocene-Quaternary aged. The surface geology of the site and its surrounding include the sedimentary sequence of Upper Pleistocene belonging to Dardanelles Group. From bottom to top it has fluvial deposits, shallow marine carbonate and clastic deposits. The direct current resistivity method with independent soundings along a profile revealed the geo-electrical model. Evaluation of both geoelectrical model sections and the surface geology reveal a proposed geological section and the aquifer boundaries. The model indicates that: (1) the clastic deposits overlie the aquifer of shallow marine carbonate deposits as wedge shaped in the survey site, (2) the shallow marine carbonate deposits are just visualized approximately 55 m into the land regarding to the evaluation of the hydrogeophysical model, (3) a wetness front is evaluated which imply that the clastic deposits reveal perched aquifer conditions. Moreover, the shallow marine carbonate deposits outcrop in the surrounding of the survey site as marine terraces due to the regional tectonic activity and bound the survey site morphologically. This situation gives opportunities for conducting further hydrogeophysical surveys on the selected locations of the vicinity of the site to reveal what the subsurface continuity of the aquifer is in the context of the regional geology and tectonic activity.

In this paper, we experimentally analyzed the feasibility of estimating soil hydraulic properties from 1.4 GHz radiometer and 0.8-2.6 GHz ground-penetrating radar (GPR) data. Radiometer and GPR measurements were performed above a sand box, which was subjected to a series of vertical water content profiles in hydrostatic equilibrium with a water table located at different depths. A coherent radiative transfer model was used to simulate brightness temperatures measured with the radiometer. GPR data were modeled using full-wave layered medium Green's functions and an intrinsic antenna representation. These forward models were inverted to optimally match the corresponding passive and active microwave data. This allowed us to reconstruct the water content profiles, and thereby estimate the sand water retention curve described using the van Genuchten model. Uncertainty of the estimated hydraulic parameters was quantified using the Bayesian-based DREAM algorithm. For both radiometer and GPR methods, the results were in close agreement with in situ time-domain reflectometry (TDR) estimates. Compared with radiometer and TDR, much smaller confidence intervals were obtained for GPR, which was attributed to its relatively large bandwidth of operation, including frequencies smaller than 1.4 GHz. These results offer valuable insights into future potential and emerging challenges in the development of joint analyses of passive and active remote sensing data to retrieve effective soil hydraulic properties.

The objective of this study is to perform a hydrogeological survey using remote sensing techniques in order to delineate target zones for groundwater exploration within terrains underlain by crystalline rocks. The study area is situated in northwestern flanks of the Red Sea Hills in the Hamissana area, Red Sea State within the Arabian Nubian Shield (ANS)
which belongs to the Pan-African Era. The region is characterized by a desert climate, where acute shortages of water is experienced. The study area is covered by the basement complex rocks (Precambrian age) which is overlain by alluvial deposits. The remotely sensing data
of Enhanced Thematic Mapper (ETM+) were used in this study in addition to Geographic Information System (GIS) to illustrate the geological features in the study area, mainly the Lineaments. The structural analysis had been applied to classify the open potential fractures that are commonly found in NW-SE and in NE-SW directions, while the closed shear fractures are oriented in N-S direction. Based on the study of lineaments, target zones of groundwater were indicated by the overlap of high-intensity opened lineaments and the low drainage intensity.

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Page 1. 12 HYDROGEOPHYSICAL CASE STUDIES AT THE REGIONAL SCALE MARK GOLDMAN1, HAIM GVIRTZMAN2, MAX MEJU3, and VLADIMIR SHTIVELMAN1 1Geophysical Institute of Israel, Israel 2Hebrew University of Jerusalem, Israel 3Lancaster University, UK ...

A talik is a layer or body of unfrozen ground that occurs in permafrost due to an anomaly in thermal, hydrological, or hydrochemical conditions. Information about talik geometry is important for understanding regional surface water and groundwater interactions as well as sublacustrine methane production in thermokarst lakes. Due to the direct measurement of unfrozen water content, surface nuclear magnetic resonance (NMR) is a promising geophysical method for noninvasively estimating talik dimensions. We made surface NMR measurements on thermokarst lakes and terrestrial permafrost near Fairbanks, Alaska, and confirmed our results using limited direct measurements. At an 8 m deep lake, we observed thaw bulb at least 22 m below the surface; at a 1.4 m deep lake, we detected a talik extending between 5 and 6m below the surface. Our study demonstrates the value that surface NMR may have in the cryosphere for studies of thermokarst lake hydrology and their related role in the carbon cycle.

Often in geophysical monitoring experiments time-lapse inversion models vary too smoothly with time, owing to the strong imprint of regularization. Several methods have been proposed for focusing the spatiotemporal changes of the model parameters. In this study, we present two generalizations of the minimum support norm, which favour compact time-lapse changes and can be adapted to the specific problem requirements. Inversion results from synthetic direct current resistivity models that mimic developing plumes show that the focusing scheme significantly improves size, shape and magnitude estimates of the time-lapse changes. Inversions of the synthetic data also illustrate that the focused inversion gives robust results and that the focusing settings are easily chosen. Inversions of full-decay time-domain induced polarization (IP) field data from a CO2 monitoring injection experiment show that the focusing scheme performs well for field data and inversions for all four Cole–Cole polarization parameters. Our tests show that the generalized minimum support norms react in an intuitive and predictable way to the norm settings, implying that they can be used in time-lapse experiments for obtaining reliable and robust results.

Glaciers are widely spread on polar and sub-polar regions but also on middle latitude mountains, where cold-dry type glaciers, polythermal glaciers and temperate-wet glaciers are respectively present. Polythermal glaciers have a cold-ice layer (temperature below the pressure melting point) overriding a temperate-ice layer. Nineteen magnetic resonance soundings were done following a 3 Km profile on Hansbreen front. Resistivity on the glacier surface, magnetic susceptibility of rocks, electromagnetic noise and total earth’s magnetic field measurements confirm that the MRS survey took place in the best conditions. MRS data show different signals amplitudes at the Larmor frequency according to the loop dimension. In a very high electrical resistive context (>2 Mega Ohms meter for glacier ice) the surveyed depth is directly related to the loop area. For small loops (30 m square loop) amplitudes around 50 nV are common as well as some decay time (T*2) above 300 ms. Enlarging the loop size (60 m square loop) it is possible to observe a decrease of the signal amplitude at the Larmor frequency (E0 < 20 nV) but also the time decay (100 ms >= T*2 >40 ms). Increasing loop sizes (90 and 120 m square loops), a slight increase in amplitude at the Larmor frequency, close to 30 nV, is observed with very high time decays (T*2 >500 ms). Ground Penetrating Radar surveys were carried out in Hansbreen at the same location as the MRS surveyed zone. Available GPR data show a water content of 2,5% on the cold-ice layer (the first 35 m depth) and 2% of water content on the temperate-ice layer but a 4% of water content can also be detected. Both geophysical methods are not convergent because some water content on ice has too short relaxation times being undetectable with conventional MRS devices. In that sense the low T*2 time decays data from large MRS loops elucidates that at the temperate-ice layer water flows by seepage through veins and microfractures at a very low rate toward the glacier bottom and a large amount of free water is close to the cold/temperate transition surface. In the cold-ice layer large T*2 time decays are common because water flows through fissures or karstic like conduits. In summary, combining the MRS and GPR techniques gives glaciologists a powerful toolkit to elucidate water flow-paths on glaciers, supercooled meltwater content and subglacial water or aquifers

A Geoelectric survey involving Vertical Electrical Sounding was carried out with the aim of using the results to delineate aquifer and assess its sustenance for adequate water supply for irrigation work in Fadama parts of some villages in Igabi Local Government Area, Kaduna state, Nigeria. The data were acquired with symmetric Schlumberger configuration at stations chosen across the study area. The acquired data were inverted with 1D Earth Imager iterative software. The interpreted results suggest four geoelectric layers. From their equivalent geologic/lithologic units, the weathered and the underlain fractured basement, which are characterized with relatively low resistivity values (14 to 217Ωm), were considered as the aquiferous layers of the study area. Suitable sites for construction of pump-fitted wells were suggested based on thickness of the aquiferous layers. On assessment of the groundwater from estimated aquifer parameters, the well yield will serve the intended irrigation purpose.

Magnetic, geoelectric and seismic refraction methods are used to prospect for groundwater in basement terrains of Wadi Sibaiya and the upstream part of Wadi El Sheikh, south Sinai. The electric resistivity of the water-bearing alluvium ranges between 150 and 260 ohm/m while that of the underlying weathered basement filled with water is about 1000 ohm/m and more. Moreover, the velocity of the refracted seismic waves in the watered alluvial deposits is more than 2000m/sec, while it is around 5000m/sec in the underlying weathered basement rocks filled with water. According to the obtained geophysical results, two sites in Wadi El Sheikh are recommended for drilling water wells. The probable depth of water table is about 40 meters.

The remediation of petroleum-contaminated soil and groundwater is a challenging task. The petroleum hydrocarbons have a long persistence in both the vadose zone and in the aquifer and potentially represent secondary and residual sources of contamination. This is particularly evident in the presence of residual free-phase. Pump-and-treat is the most common hydrocarbon decontamination strategy. Besides, it acts primarily on the water dissolved phase and reduces concentrations of contaminants to an asymptotic trend. This study presents a case of enhanced light non-aqueous phase liquid (LNAPL) remediation monitored using noninvasive techniques. A pilot-scale field experiment was conducted through the injection of reagents into the subsoil to stimulate the desorption and the oxidation of residual hydrocarbons. Geophysical and groundwater monitoring during pilot testing controlled the effectiveness of the intervention, both in terms of product diffusion capacity and in terms of effective ...

The Astaneh-Kouchesfahan Plain, an extensive and productive aquifer system in Iran, is located in the south Caspian Sea basin which is part of the Alborz tectonic range in the Alpine fold belt. A permeable aquifer system provides water for industrial, agricultural and domestic uses. Geological and geophysical studies indicate a number of important facts about the groundwater system. For this reason, detailed regional geological, tectonic and geophysical data were gathered to better understand the behavior of hydrogeological zones in the system. Geological studies show that the area is predominantly covered by recent alluvium, which consists of Pleistocene and Holocene stream deposits, coastal deposits, beach deposits and alluvial fan deposits. The bedrock mainly consists of impermeable clay of the Mesozoic era. Also, based on available geological cross sections, geophysical surveys, and well logs, it is shown that the system contains an unconfined, shallow Quaternary alluvial aquifer which is composed of heterogeneous sequences of relatively coarse grained gravel and sand interconnected with different thicknesses of silt and clay. The final results of this study are extremely useful for Geo-technical activities, environmental strategies, and water resource management.

Accurate estimates of surface soil moisture are essential in many research fields, including agriculture, hydrology, and meteorology. The objective of this study was to evaluate two remote-sensing methods for mapping the soil moisture of a bare soil, namely, L-band radiometry using brightness temperature and ground-penetrating radar (GPR) using surface reflection inversion. Invasive time-domain reflectometry (TDR) measurements were used as a reference. A field experiment was performed in which these three methods were used to map soil moisture after controlled heterogeneous irrigation that ensured a wide range of water content. The heterogeneous irrigation pattern was reasonably well reproduced by both remote-sensing techniques. However, significant differences in the absolute moisture values retrieved were observed. This discrepancy was attributed to different sensing depths and areas and different sensitivities to soil surface roughness. For GPR, the effect of roughness was excluded by operating at low frequencies (0.2-0.8 GHz) that were not sensitive to the field surface roughness. The root mean square (rms) error between soil moisture measured by GPR and TDR was 0.038 m 3 · m −3 . For the radiometer, the rms error decreased from 0.062 (horizontal polarization) and 0.054 (vertical polarization) to 0.020 m 3 · m −3 (both polarizations) after accounting for roughness using an empirical model that required calibration with reference TDR measurements. Monte Carlo simulations showed that around 20% of the reference data were required to obtain a good roughness calibration for the entire field. It was concluded that relatively accurate measurements were possible with both methods, although accounting for surface roughness was essential for radiometry.

We applied inverse modelling of zero-offset, air-raised ground-penetrating radar (GPR) data to measure soil surface water contents over a bare agricultural field. The GPR system consisted of a vector network analyser combined with a low-frequency 0.2–2.0 GHz off-ground monostatic horn antenna, thereby setting up an ultra-wideband stepped-frequency continuous-wave radar. A fully automated platform was created by mounting the radar system on a truck for real-time data acquisition. An antenna calibration experiment was performed by lifting the whole setup to different heights above a perfect electrical conductor. This calibration procedure allowed the flittering out of the antenna effects and antenna-soil interactions from the raw radar data in the frequency domain. To avoid surface roughness effects, only the lower frequency range of 0.2–0.8 GHz was used for signal processing. Inversions of the radar data using the Green’s functions were performed in the time domain, focusing on a time window containing the surface reflection. GPR measurements were conducted every 4 m along a transect of 100 m. In addition, five time-domain reflectometry measurements were randomly recorded within the footprint of the GPR antenna. A good agreement was observed between the GPR and time-domain reflectometry soil water content estimates, as compared to the previous study performed at the same test site using a higher frequency 0.8–1.6 GHz horn antenna. To monitor the dynamics of soil water content, a pair of time-domain reflectometry probes was installed at 8 cm depth near the footprint of the GPR antenna and both time-domain reflectometry and GPR measurements were carried out for a period of 20 days. A good agreement of the trend was observed between the time-domain reflectometry and GPR time-lapse data with respect to several precipitation events. The proposed method and truck-mounted setup appear to be promising for the real-time mapping and monitoring of surface soil moisture contents at the field scale.

Low frequency electromagnetic induction (EMI) is becoming a useful tool for soil characterization due to its fast measurement capability and sensitivity to soil moisture and salinity. In this research, a new EMI system (the CMD mini-Explorer) is used for subsurface characterization of soil salinity in a drip irrigation system via a joint inversion approach of multiconfiguration EMI measurements. EMI measurements were conducted across a farm where Acacia trees are irrigated with brackish water. In situ measurements of vertical bulk electrical conductivity (r b) were recorded in different pits along one of the transects to calibrate the EMI measurements and to compare with the modeled electrical conductivity (r) obtained by the joint inversion of multiconfiguration EMI measurements. Estimates of r were then converted into the universal standard of soil salinity measurement (i.e., electrical conductivity of a saturated soil paste extract-EC e). Soil apparent electrical conductivity (EC a) was repeatedly measured with the CMD mini-Explorer to investigate the temperature stability of the new system at a fixed location, where the ambient air temperature increased from 26 C to 46 C. Results indicate that the new EMI system is very stable in high temperature environments, especially above 40 C, where most other approaches give unstable measurements. In addition, the distribution pattern of soil salinity is well estimated quantitatively by the joint inversion of multicomponent EMI measurements. The approach of joint inversion of EMI measurements allows for the quantitative mapping of the soil salinity distribution pattern and can be utilized for the management of soil salinity.

Precise measurement of soil hydraulic properties at field scales is one of the prerequisites to simulate subsurface flow and transport processes, which is crucial in many research and engineering areas. In our study, we numerically analyze uniqueness and stability for integrated hydrogeophysical inversion of time-lapse, off-ground ground-penetrating radar (GPR) data in estimating the unsaturated soil hydraulic properties. In the inversion, hydrodynamic modeling based on the one-dimensional (1-D) Richards equation is used to physically constrain a full-waveform radar electromagnetic model. Synthetic GPR data, in terms of 3-D multilayered media Green's functions, were generated for three different textured soils (coarse, medium, and fine) and assuming different infiltration events. Inversion was performed iteratively to estimate three key soil hydraulic parameters (a, n, and K s) of the Mualem-van Genuchten model using the global multilevel coordinate search optimization algorithm. For the coarse-and medium-textured soils, inversions converged to the actual solution for all scenarios. For the fine soil, estimation errors occurred, mainly because of the higher attenuation of the electromagnetic waves in such a soil (high electric conductivity). The procedure appeared to be generally stable with respect to possible errors in the hydrodynamic and petrophysical model parameterization. However, we found that particular attention should be given to an accurate estimation of the saturated water content and infiltration flux for real field applications. The results from our numerical experiments suggest that, in theory, the proposed method is promising for the noninvasive identification of the shallow soil hydraulic properties at the field scale with a high spatial resolution.

The remediation of petroleum-contaminated soil and groundwater is a challenging task. The petroleum hydrocarbons have a long persistence in both the vadose zone and in the aquifer and potentially represent secondary and residual sources of contamination. This is particularly evident in the presence of residual free-phase. Pump-and-treat is the most common hydrocarbon decontamination strategy. Besides, it acts primarily on the water dissolved phase and reduces concentrations of contaminants to an asymptotic trend. This study presents a case of enhanced light non-aqueous phase liquid (LNAPL) remediation monitored using noninvasive techniques. A pilot-scale field experiment was conducted through the injection of reagents into the subsoil to stimulate the desorption and the oxidation of residual hydrocarbons. Geophysical and groundwater monitoring during pilot testing controlled the effectiveness of the intervention, both in terms of product diffusion capacity and in terms of effective ...