Investigation of seawater intrusion in the Dibdibba Aquifer using 2D resistivity imaging in the area between Al-Zubair and Umm Qasr,southern Iraq

Electrical resistivity surveying for delineating seawater intrusion was performed in the Dibdibba aquifer in the area between the cities of Al-Zubair–Safwan and Al-Zubair–Umm Qasr in the vicinity of Khor AL-Zubair Channel, Basrah governorate, southern Iraq. Fourteen 2D resistivity profiles with a total length of 14 km were collected in the study area. The resistivity sections were compared with lithological data extracted from 11 boreholes. Thirty-nine groundwater samples were collected within the area and analyzed for chemical constituents; internal hydrogeological reports and unpublished studies were also evaluated. Results reveal the existence of three major resistivity layers, ranging from 0.1 to 130 Ωm at various depths and locations. The first layer has very low electrical resistivity (0.1–5 Ωm) representing a layer saturated with saltwater intruded from Khor AL-Zubair Channel. The second layer shows resistivity in the range of 5–130 Ωm, attributed to a transition zone and an unaffected zone saturated with brackish groundwater. The last resistivity layer (<?3 Ωm) represents coarse-grain sediments saturated with saline groundwater. Furthermore, a hard clay bed (Jojab) appears with a resistivity of 3–7 Ωm in all 2D imaging lines within a depth of 20–28 m. Electrical conductivity (EC) measurements from seven wells collected in 2014 and 2016 show a positive EC difference increasing landward with an average increase of 1927 µS/cm. In addition, six chemical relationships (Na/Cl, [Ca?+?Mg]/[HCO₃?+?SO₄], SO₄/HCO₃, SO₄/Cl, Mg/Ca and Cl/[HCO₃?+?CO₃]) are used to detect the source of salinity in groundwater. This study proves that extensive use of high-resolution 2D imaging sections, alongside lithological and hydrogeological data, can serve as a useful tool to delineate the boundaries between aquifers, identify hydraulic boundaries between groundwater with different salinities and allocate hard clay layers between the upper and lower Dibdibba aquifer. In general, the combination of 2D imaging and hydrochemistry enables conceptualization of the hydrogeological situation in the subsurface and characterization of the salinity source, here seawater intrusion, in the study area. There have been no studies published so far on the characteristics of saltwater intrusion in the study area, and this study is considered to be important for monitoring and studying the intrusion and regression of seawater.     

Assessment of seawater mixing in a coastal aquifer by high resolution electrical resistivity tomography

Seawater intrusion is a major problem in urbanized coastal regions of India which is due to over exploitation of groundwater for various purposes. This study was carried out with the objective of assessing the zone of mixing between seawater and groundwater in the coastal aquifer in south of Chennai, Tamil Nadu, India using high resolution electrical resistivity tomography. High resolution electrical resistivity tomography was carried out in five profiles perpendicular to the sea using IRIS make SYSCAL Pro-96 system with 2.5 m or 5 m inter-electrode separation. The maximum length of the profile was 170 m which resulted in a depth of investigation of 28.7 m. The apparent resistivity measured in this area varies from 0.3 ohm-m to 30,000 ohm-m. The apparent resistivity of saturated zone decreases towards the sea, indicating the influence of seawater. This was also confirmed by measuring the electrical conductivity of groundwater, which gradually increases from 156 μS/cm to 3430 μS/cm towards the sea. Further, the concentration profiles of electrical conductivity, sodium, chloride and chloride / bicarbonate ratio are compared with the high resolution electrical resistivity tomography profile. The distance of influence of seawater is comparatively high in northern part than in southern part of the area. The high resolution electrical resistivity tomography was effectively used to determine the effect of seawater mixing with groundwater.     

咸淡水界面位置确定的综合方法(TEcG)及其应用

准确确定咸淡水界面位置是评价咸水入侵范围的前提。对于咸淡水界面位置的确定,传统研究以水化学法和物探法为主。为克服单一使用传统方法造成的人力、物力和财力的大量浪费,以莱州湾西南岸广饶县小清河以南咸水入侵区为研究对象,在综合分析研究区地下水开采现状、水化学监测结果的基础上,选择3个典型断面,采用水化学法中的野外现场电导率法,快速判断咸淡水界面大致位置（某两眼监测井之间）;再在一咸一淡的两眼监测井之间,采用高密度电阻率法快速、准确地确定咸淡水界面的空间分布。结果表明：该地区的地下水电导率若大于1.61 mS/cm,即可认为此处受到咸水入侵;咸淡水界面位置的视电阻率特征值为11~13 Ω·m,咸淡水界面附近咸水体呈舌状入侵并主要发生在地表以下13 m内的浅层地下水中。     

Effect of saltwater intrusion on groundwater environment in Weihe River downstream,Shandong Province,China

Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level, this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area. According to monitoring data of groundwater quality, the distribution characteristics of macro component are analyzed, and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment. Concerning the influence degree of groundwater environment, the study area is divided into brine area, seriously influenced area, moderately influenced zone, slightly influenced zone and uninfluenced zone. The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources.     

Effect of saltwater intrusion on groundwater environment in Weihe River downstream,Shandong Province,China

Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level,this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area.According to monitoring data of groundwater quality,the distribution characteristics of macro component are analyzed,and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment.Concerning the influence degree of groundwater environment,the study area is divided into brine area,seriously influenced area,moderately influenced zone,slightly influenced zone and uninfluenced zone.The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources.     

Using airborne geophysical data in identifying tectonic lineaments in east of Iran

In this paper we tried to identify the main tectonic lineaments in Eastern Iran including Lut block and Sistan suture zone from the airborne geomagnetic data together with tilt filter. As the map of obtained lineaments from airborne geomagnetic data has been studied, four distinct set of lineaments has been identified: (i) north–south, (ii) east–west, (iii) northeast–southwest, and (iv) northwest–southwest that are concurrently with structural zones and area’s big faults. New faults which have been identified in this investigation are lineaments with trend northeast–southwest and east–west. The depth of these lineaments has been calculated through Euler modeling. Magnetic lineaments trending east–west have the most depth, so these lineaments are related to basement faults.     

山东省广饶县地下水位多年动态及其地质环境效应分析

山东省广饶县地下淡水资源丰富,是本区工农业生产和生活用水的重要水源,长期大量开采地下水引发了地下水降落漏斗、咸水入侵、地面沉降等地质环境问题.通过对广饶县地下水多年监测资料的整理和分析,揭示了本区地下水水位的变化规律,预测了地下水水位的变化趋势.分析表明:在现状开采条件下,浅层地下水降落漏斗已基本稳定,无加重趋势.考虑...     

Delineation of saltwater intrusion into the freshwater aquifer of Lekki Peninsula,Lagos, Nigeria

Recently, the deterioration of water quality in the coastal zones of Lekki Peninsula area of Lagos due to saltwater infiltration into the freshwater aquifer has become a major concern. With the aim of providing valuable information on the hydrogeologic system of the aquifers, the subsurface lithology and delineating the groundwater salinity, vertical electrical resistivity (VES) sounding survey was carried out utilizing surface Schlumberger electrode arrays, and electrode spacing varying between 1 and 150 m. The DC resistivity surveys revealed significant variations in subsurface resistivity. Also, the VES resistivity curves showed a dominant trend of decreasing resistivity with depth (thus increasing salinity). In general, the presence of four distinct resistivity zones were delineated viz.: the unconsolidated dry sand (A) having resistivity values ranging between 125 and 1,028 Ωm represent the first layer; the fresh water-saturated soil (zone B) having resistivity values which correspond to 32–256 Ωm is the second layer; the third layer (zone C) is interpreted as the mixing (transition) zone of fresh with brackish groundwater. The resistivity of this layer ranges from 4 to 32 Ωm; while layer four (zone D) is characterized with resistivities values generally below 4 Ωm reflecting an aquifer possibly containing brine. The rock matrix, salinity and water saturation are the major factors controlling the resistivity of the formation. Moreover, this investigation shows that saline water intrusion into the aquifers can be accurately mapped using surface DC resistivity method.     

A comparative study of artificial neural networks,Bayesian neural networks and adaptive neuro-fuzzy inference system in groundwater level prediction

Predictive modeling of hydrological time series is essential for groundwater resource development and management. Here, we examined the comparative merits and demerits of three modern soft computing techniques, namely, artificial neural networks (ANN) optimized by scaled conjugate gradient (SCG) (ANN.SCG), Bayesian neural networks (BNN) optimized by SCG (BNN.SCG) with evidence approximation and adaptive neuro-fuzzy inference system (ANFIS) in the predictive modeling of groundwater level fluctuations. As a first step of our analysis, a sensitivity analysis was carried out using automatic relevance determination scheme to examine the relative influence of each of the hydro-meteorological attributes on groundwater level fluctuations. Secondly, the result of stability analysis was studied by perturbing the underlying data sets with different levels of correlated red noise. Finally, guided by the ensuing theoretical experiments, the above techniques were applied to model the groundwater level fluctuation time series of six wells from a hard rock area of Dindigul in Southern India. We used four standard quantitative statistical measures to compare the robustness of the different models. These measures are (1) root mean square error, (2) reduction of error, (3) index of agreement (IA), and (4) Pearson’s correlation coefficient (R). Based on the above analyses, it is found that the ANFIS model performed better in modeling noise-free data than the BNN.SCG and ANN.SCG models. However, modeling of hydrological time series correlated with significant amount of red noise, the BNN.SCG models performed better than both the ANFIS and ANN.SCG models. Hence, appropriate care should be taken for selecting suitable methodology for modeling the complex and noisy hydrological time series. These results may be used to constrain the model of groundwater level fluctuations, which would in turn, facilitate the development and implementation of more effective sustainable groundwater management and planning strategies in semi-arid hard rock area of Dindigul, Southern India and alike.     

Integrated studies for characterization of lineaments used to locate groundwater potential zones in a hard rock region of Karnataka, India

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.The online version of the original article can be found at     

Integrated studies for characterization of lineaments used to locate groundwater potential zones in a hard rock region of Karnataka, India

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.An erratum to this article can be found at     

Using DC resistivity method to characterize the geometry and the salinity of the Plioquaternary consolidated coastal aquifer of the Mamora plain,Morocco

The Direct Current resistivity method was applied to the consolidated coastal Plioquaternary aquifer of Mamora plain, located on the Atlantic coast of Morocco. The aim is to determine the depth of the base of the saturated zone in the aquifer and to help in imaging lateral and vertical distribution of groundwater salinity. The geoelectric survey showed four geoelectric formations with the following electrical resistivities from top to bottom: 20–80, 200–2000, 200–300 and 5–70 Ohm m. The latter designates the basement of the aquifer constituted of marls and sandy marls. The mean resistivity of 250 Ohm m designates the aquifer formation. It decreases to less than 25% of its initial values for the soundings near the shore, reflecting the oceanic impact on the aquifer formation resistivity. The contour map shows that the basement of the saturated zone in the aquifer is deeper in the Northwest near the Sebou River estuary with values up to 70 m below sea level. This results in a larger thickness of the saturated zone of the aquifer leading to a consequent hydraulic potential. On the other hand, it has been deduced that the extent of marine intrusion inside the continent can be governed by human activities, natural properties and substratum geometry of the aquifer as well as by ecological factors. An optimal network of electrical soundings has been proposed for the monitoring of saltwater intrusion.     

Ground penetrating radar for groundwater exploration in granitic terrains: A case study from Hyderabad

The Ground Penetrating Radar (GPR) is a newly developing geophysical tool for imaging the sub-surface and is potentially useful in groundwater exploration. We test its usefulness in characterizing a groundwater rich lineament near Gajularamaram in the Hyderabad granite terrain, where groundwater is limited to soil, weathering zone and lineaments. The lineament is 2 km long and 50–100 m wide, and oriented in WNW-ESE direction. It is characterized by many closely spaced sub-vertical fractures and faults, majority of which are parallel to the lineament. On either sides of the lineament, sub-horizontal sheet joints are abundant. The lineament is saturated with groundwater that discharge as springs at some places. About 450 m long, 400–100 MHz GPR data (～5–30 m depth) were acquired along five profiles across the lineament. In the lineament, soil thickness varies from ～0.5 m to 5 m, and is underlain by weathered granite. In the WNW part, a thick weathering zone (～15 m) is present and a 10 m wide vertical anomaly zone (lineament) is also present. The presence of shallow reflectors at 1 m depth in the lineament is attributed to the groundwater surface. The GPR images reveal many sub horizontal to gently dipping reflectors, which are interpreted to be the sheet joints. The GPR data clearly reveal the saturated lineament, from which groundwater may migrate laterally to long distance through the sheet joints. We demonstrate the GPR as a rapid geophysical tool that can be used successfully to explore the nearsurface groundwater.     

Three-dimensional hydrostratigraphical modelling to support evaluation of recharge and saltwater intrusion in a coastal groundwater system in Vietnam

Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.     

Use of time-domain electromagnetic (TDEM) method to investigate seawater intrusion in the Lebna coastal aquifer of eastern Cap Bon,Tunisia

A multi-method geophysical survey, using time-domain electromagnetic (TDEM) fields, is conducted on the north-eastern coastal aquifer of Cap Bon, Tunisia. The aim of the study is to investigate the inland extent saltwater intrusion, to estimate the fresh-saltwater transition zone, and to characterize the lithologic spatial variability of the underground layers. Moreover, the TDEM is used to determine both fluid resistivity and bulk resistivity which are required to calculate the porosity by applying the Archie’s equation. The survey of TDEM profiles is carried out along the left and right overbanks of the Lebna river from the coast until the Lebna dam. The interpretation and the analysis of these profiles allow us to better identify the flux exchanges between the river and the underlying aquifer. On the basis of the 1D and 2D longitudinal and transversal resistivity profiles as well as the existing boreholes data and groundwater quality, it seems that the freshwater-saltwater interface is moving forward inland. Furthermore, electromagnetic results combined to the Archie’s law show that the porosity values are at the ranges of 12–36 and 5–31% for the Quaternary outcropping and Pliocene formation, respectively.     

Structural setup of Ras Banas area,Red Sea,Egypt, as inferred from aeromagnetic data

This study deals with the evaluation of the structural setup of the Ras Banas area on the northwestern part of the Red Sea by using magnetic data. Different analyzing techniques were applied to achieve this goal including regional-residual separation, trend analysis, depth estimation, Euler deconvolution, horizontal gradient, analytic signal, and magnetic modeling. The results of these techniques were used to construct a deep-seated structural feature map.Lineament analysis indicates that the area was mainly affected by the NW, WNW, and NE tectonic trends. The magnetic modeling was performed along four profiles supported by Euler deconvolution, horizontal gradient, and analytic signal profiles. The modeled profiles show that the basement rocks composed of uplifted and down-faulted blocks at different depths as well as step-like structure. The basement rocks seem to be acidic in nature intruded by basic/ultrabasic dikes. Generally, the magnetic susceptibility ranges from 0.0003 to 0.04 cgs indicating acidic to basic/ultrabasic rock composition. The basement relief map shows an irregular basement surface, which varies greatly in depth from 1 to 5.6 km below sea level. The deep-seated structure map shows that the basement was highly affected by two main fault trends in the NW and NNE directions. The NW trending structures were intersected by younger left lateral NNE transform faults. These cross-faults dissect the area into a number of alternated and elongated blocks.     

Salinity mapping of coastal groundwater aquifers using hydrogeochemical and geophysical methods: a case study from north Kelantan,Malaysia

Integrated hydrogeochemical and geophysical methods were used to study the salinity of groundwater aquifers along the coastal area of north Kelantan. For the hydrogeochemical investigation, analysis of major ion contents of the groundwater was conducted, and other chemical parameters such as pH and total dissolved solids were also determined. For the geophysical study, both geoelectrical resistivity soundings and reflection seismic surveys were conducted to determine the characteristics of the subsurface and groundwater contained within the aquifers. The pH values range from 6.2 to 6.8, indicating that the groundwater in the study area is slightly acidic. Low content of chloride suggests that the groundwater in the first aquifer is fresh, with an average concentration of about 15.8 mg/l and high geoelectrical resistivity (>45 ohm m). On the other hand, the groundwater in the second aquifer is brackish, with chloride concentration ranging from 500 mg/l to 3,600 mg/l and very low geoelectrical resistivity (<45 ohm m) as well as high concentration of total dissolved solids (>1,000 mg/l). The groundwater in the third aquifer is fresh, with chloride concentrations generally ranging from 2 mg/l to 210 mg/l and geoelectrical resistivity of greater than 45 ohm m. Fresh and saltwater interface in the first aquifer is generally located directly in the area of the coast, but, for the second aquifer, both hydrogeochemical and geoelectrical resistivity results indicate that the fresh water and saltwater interface is located as far as 6 km from the beach. The considerable chloride ion content initially suggests that the salinity of the groundwater in the second aquifer is probably caused by the intrusion of seawater. However, continuous monitoring of the chloride content of the second aquifer indicated no significant changes with time, from which it can be inferred that the salinity of the groundwater is not affected by seasonal seawater intrusion. Schoeller diagrams illustrate that sulphate concentrations of the groundwater of the second aquifer are relatively low compared to those of the recent seawater. Therefore, this result suggests that the brackish water in the second aquifer is probably from ancient seawater that was trapped within the sediments for a long period of time, rather than due to direct seawater intrusion.     

Chemical and physical parameters as trace markers of anthropogenic-induced salinity in the Agua Amarga coastal aquifer (southern Spain)

Agua Amarga coastal aquifer in southern Spain has been the subject of chemical and physical measurements since May 2008 in order to monitor the potential effects of water withdrawal for the Alicante desalination plants on the salt marsh linked to the aquifer. Electrical conductivity contour maps and depth profiles, piezometric-head contour maps, hydrochemical analyses, isotopic characterizations and temperature depth profiles show not only the saltwater intrusion caused by water abstraction, but also the presence of a pronounced convective density-driven flow below the salt marsh; this flow was a consequence of saltwork activity in the early 1900s which generated saline groundwater contamination. The influence of a seawater recharge programme, carried out over the salt marsh in 2009–2010, on the diminishing groundwater salinity and the recovery of groundwater levels is also studied. Based on collected field data, the project provides a deeper understanding of how these successive anthropogenic interventions have modified flow and mixing processes in Agua Amarga aquifer.     

Coastal-zone shallow-aquifer characterization study using geoelectrical and geochemical methods in Zirconium Complex,Atomic Energy,Pazhayakayal, Thoothukudi,India

Groundwater is a very important component of water resources in coastal aquifers in Thoothukudi. It has been established that the groundwaters in the coastal zone of the Zirconium Complex, Pazhayakayal, Thoothukudi district, Tamilnadu, India, are subjected to wave and tidal impact. The groundwater quality was studied by hydrogeological methods, 2D electrical resistivity imaging (ERI) techniques (six profiles), 11 Wenner vertical electrical sounding (VES), and well log analysis. Also, nine geochemical water samples were taken from the study area. The 2D ERI and VES surveys were carried out using WGMD-4 Ltd., Chennai, resistivity meter, multicore cable, and multielectrodes with Wenner array. The collected resistivity data were interpreted using the Res2DINV software. The research shows that the groundwaters are the result of the paleoriver flow along the Tamirabarani Channel in the western area and of the seawater intrusion in the eastern area. The fresh water is characterized by resistivity of about 10–100 Ohm?m in the study area. The resistivity of 10–50 Ohm?m indicates that the subsurface section is made up of sand, clay, and caliche. Resistivity values of more than 200 Ohm?m are specific to sand dunes. The very low resistivity (<5 Ohm?m) layer might be due to the seawater intrusion in the study area. Six water samples from the well drilled in the coastal area were analyzed, which made it possible to determine the concentrations of major and trace elements in the groundwaters. These data were used to establish the seawater intrusion and coastal environment characteristics in the study area.     

Sustainability analysis of groundwater resources in a coastal aquifer, Alabama

Fort Morgan Peninsula is an attached portion of a dynamic barrier complex in the northern Gulf of Mexico and is a large tourist area that brings in a significant amount of revenue for Alabama. Many of the hotels and tourist attractions depend on the groundwater as their water supply. The over-withdrawal of groundwater and saltwater intrustion will have a negative impact on the ecology, tourism and economy if groundwater resources are not properly monitored and managed. In this study a calibrated groundwater flow model was used to analyze the sustainability of groundwater resources at Fort Morgan Peninsula. Detailed flow budgets were prepared to check the various components of inflow and outflow under different water use and climatic conditions. The results indicated the locations where groundwater was over-pumped and subjected to saltwater intrusion, or will be subjected to saltwater intrusion under a range of projected water use and climatic conditions.