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.     

Assessment of integrated electrical resistivity data on complex aquifer structures in NE Nuba Mountains – Sudan

Two geophysical techniques were integrated to map the groundwater aquifers on complex geological settings, in the crystalline basement terrain in northeast Nuba Mountains. The water flow is structurally controlled by the northwest–southeast extensional faults as one of several in-situ deformational patterns that are attributed to the collision of the Pan-African oceanic assemblage of the Nubian shield against the pre-Pan African continental crust to the west. The structural lineaments and drainage systems have been enhanced by the remote sensing technique. The geophysical techniques used are: vertical electrical soundings (VES) and electrical resistivity tomography (ERT), in addition to hydraulic conductivity measurements. These measurements were designed to overlap in order to improve the producibility of the geophysical data and to provide a better interpretation of the hydrogeological setting of the aquifer complex structure. Smooth and Block inversion schemes were attempted for the observed ERT data to study their reliability in mapping the different geometries in the complex subsurface. The VES data was conducted where ERT survey was not accessible, and inverted smoothly and merged with the ERT in the 3D resistivity grid. The hydraulic conductivity was measured for 42 water samples collected from the distributed dug wells in the study area; where extremely high saline zones were recorded and have been compared to the resistivity values in the 3D model.     

Geophysical characteristics of Wadi Hanifah water system, Riyadh, Saudi Arabia

Integrated geophysical techniques including resistivity image, vertical electrical sounding (VES), and seismic refraction have been conducted to investigate the Wadi Hanifah water system. The groundwater in Wadi Hanifah has problems caused by the high volumes of sewage water percolating into the ground. The combination of VES, resistivity image, and seismic refraction has made a valuable contribution to the identification of the interface between the contaminated and fresh water in Wadi Hanifah area. The contaminated groundwater has lower resistivity values than fresh groundwater due to the higher concentration of ions which reduces the resistivity. Resistivity image and sounding in this area clearly identified the nature of the lithological depth and proved useful at identifying water-bearing zones. Fresh groundwater was found in the study area at a depth of 100 m within the fractured limestone. Water-bearing zones occur in two aquifers, shallow contaminated water at 10 m depth in alluvial deposits and the deeper fresh water aquifer at a depth of about 100 m in fractured limestone. The interface between the contaminated water (sanitary water) and fresh water marked out horizontally at 100 m distance from the main channel and vertically at 20 m depth.     

Electrical resistivity and hydrochemical indicators distinguishing chemical characteristics of subsurface pollution at Cuddalore coast,Tamil Nadu

Electrical resistivity methods are applied extensively for shallow sub-surface objectives but it has constraints in distinguishing the chemical characteristics of the medium. However, this complexity can be resolved by integrated investigations where geophysical anomaly would be validated with hydro-geochemical data. The present study highlights the notable importance of integrated geophysical and hydrogeological investigations in demarcating sub-surface pollution due to saline water intrusion and industrial effluents at Cuddalore coast in India. Geophysical scanning encompassing a total of 35 vertical electrical sounding (VES) were validated with drilling lithologs, water level and water quality parameters from a network of 125 observation wells at a test site of 17 km². To understand the spatial variation of sub-surface contamination, two profiles of apparent resistivity sections were generated covering VES points parallel to the coast. Results revealed that, the low order of resistivity range 3 to 10 Ω-m (up to 30–40 m depth) and total dissolved solids range 2000 to 10,000 mg/l of groundwater reflects sub-surface contamination but cannot distinguish kind of salinity which is further verified by chemical analysis of Ca²⁺ (1200–2041 mg/l), SO₄ ^2? (3000–9480 mg/l) which confirms the gypsum pollution and Na⁺ (750–1000 mg/l), Cl^? (1000–2000 mg/l) designate the marine water contamination. Further, static groundwater head measurements demarcate the study area into above mean sea level (MSL) and below MSL zones. This study has provided a rapid and comprehensive picture about spatial variations of groundwater contamination which can help in planning, protection and safe management of coastal aquifers in India and worldwide.     

Geophysical,geochemical and hydrological analyses of water-resource vulnerability to salinization: case of the Uburu-Okposi salt lakes and environs,southeast Nigeria

Until this study, the location and depth of the saline units in Uburu-Okposi salt lake areas and environs have been unknown. This study aimed at delineating the saline lithofacies and dispersal configurations to water bodies, using electrical geophysical methods such as constant separation traversing (CST) and vertical electrical sounding (VES). Results showed weathered zones that represent aquifers mostly at the fourth geoelectric layer: between upper layered aquitards and underlying aquitards at depths 30–140 m. Lateral distribution of resistivity variance was defined by the CST, whereas the VES tool, targeted at low-resistivity zones, detected isolated saline units with less than 10 ohm-m at depths generally >78 m. The saline lithofacies were suspected to link freshwater zones via shear zones, which steer saline water towards the salt lakes and influence the vulnerability of groundwater to salinization. The level of salinization was verified by water sampling and analysis, and results showed general alkaline water type with a mean pH of 7.66. Water pollution was indicated: mean total dissolved solids (TDS) 550 mg/l, electrical conductivity (EC) 510 μS/cm, salinity 1.1‰, Cl^? 200 mg/l, N0₃ ^?35.5 mg/l, Na⁺ 19.6 mg/l and Ca²⁺ 79.3 mg/l. The salinity is controlled by NaCl salt, as deduced from correlation analysis using the software package Statistical Product for Service Solutions (SPSS). Generally, concentrations of dissolved ions in the water of the area are enhanced via mechanisms such as evaporation, dissociation of salts, precipitation run off and leaching of dissolved rock minerals.     

Vertical electrical sounding (VES) and multi-electrode resistivity in environmental impact assessment studies over some selected lakes: a case study

A combined geophysical investigation consisting of vertical electrical sounding (VES) and multielectrode system was carried out to map the subsurface resistivity in all major lakes which are highly polluted by the discharge of sewage and other chemical effluents in greater Hyderabad, India. The structural features identified in the study area play a major role in groundwater flow and storage. The interpretation of geophysical data and lithologs indicates that a silt/clay zone (predominantly silt) has a thickness of 5–10 m all along the drainage from Patelcheruvu to the Musi River. The silt/clay zone inferred close to the lakes is a mixture of clay, silt and sand with more silt content as indicated from the lithologs during drilling. The low resistivity values obtained can be attributed to the pollutant accumulated in the silt which can reduce the resistivity values. Further, the TDS of the water samples in these wells are more than 1,000 mg/l which further confirms the above scenario. The pollution spread is less in the upstream areas whereas it is more in the downstream which can be attributed to the shallow water table conditions and also due to the interaction of surface water and groundwater.     

Hydrological characterization of Budge Budge and Dum Dum areas of south and north 24 Parganas districts,West Bengal using geoelectric and geochemical methods

Integrated geoelectric, geological and geochemical investigations are carried out in Budge Budge and Dum Dum areas of south and north 24 Parganas district for ascertaining the prevailing hydrological condition and aquifer characteristic with chemical qualities of groundwater for drinking and irrigation purposes. The proposed areas are constituted of alluvium and marine sediments of Quaternary age being a part of Gangetic delta. Vertical electrical soundings (VES) of Budge Budge have delineated four to six layers consisting of top soils, the brackish water zone, clay layer, first fresh water zone, another clay layer and the bottom-most(sixth layer) second fresh water bearing zone. The first fresh water zone is located at a depth of 128 m with thickness of 43 m having resistivity range of 32 ohm.m to 37 ohm.m for VES locations BB2 and BB3. The resistivity of the deeper second fresh water bearing zone is varying from 47 ohm.m to 51 ohm.m. The interpreted VES results significantly correspond with the borehole litholog of Budge Budge area. Similar VES results are also obtained for Dum Dum area showing promising potential aquifer zone especially for VES locations DD3 and DD4. A litho-resistivity relation is also determined for the area. Total TDS content of Budge Budge ground water samples are ranging from 720 mg/l to 4400 mg/l and same is ranging from 1012 mg/l to 1930mg/l for Dum Dum ground water samples. According to IS standard, the value of major cations and anions are near to the permissible limit for Dum Dum but same is not observed in Budge Budge for drinking and irrigation purpose excepting location G7. According to Piper trilinear diagram, the ground water in Budge Budge area is sulphate rich type and in Dum Dum it is fresh in nature. Chemically, the groundwater samples from Dum Dum and Budge Budge is classified as (Ca+Mg+Cl+SO₄) facies. The geochemical parameters like total hardness (TH), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), Kelly’s ratio (KR), magnesium ratio (MR), residual sodium carbonate (RSC), corrosivity ratio (CR), Gibb’s ratio-I&II (GR-I & GR-II), chloro alkaline indices (CAI-I & CAI-II), permeability index (PI), sea water contamination (SWC) are also determined for better understanding of the quality of groundwater in the above areas.     

The hydrogeology of Adama-Wonji basin and assessment of groundwater level changes in Wonji wetland,Main Ethiopian Rift: results from 2D tomography and electrical sounding methods

Rise of groundwater level becomes an emerging concern at Wonji irrigation field, Main Ethiopian Rift. An integrated study based on geophysical resistivity methods is conducted at Wonji wetland to understand the link between irrigation water and the shallow aquifer system as well as to confirm the current concern of groundwater rise. The study was also intended to improve the uncertainty of understanding the hydrogeology of Wonji wetland including the extent and direction of groundwater–surface water interaction. The vertical and horizontal contacts between the different geological series of the Wonji area are resolved with 2D high-resolution geophysical imaging. Results from both VES and 2D tomography show low resistivity layers under Wonji irrigation field with narrow ranges in resistivity variation which corresponds to a homogeneous saturated layer. The geoelectric sections reveal two fault systems running NW–SE and N–S directions which impede lateral groundwater flow. Furthermore, groundwater is converged towards the Wonji irrigation site strained by these fault systems. The geophysical results show strong link between irrigation water and the shallow unconfined aquifer as well as among the local and regional flow systems.     

Geoelectric and geochemical studies for hydrological characterization of canning and adjoining areas of South 24 Parganas district,West Bengal

Integrated geoelectric and geochemical investigation were carried out in the Canning and adjoining areas to assess the prevailing groundwater conditions and chemical quality of groundwater. Geologically, the area is constituted of alluvial sediments of Quaternary age. Vertical electrical soundings (VES) in the area of investigation mostly show six layers consisting of top soil, saline water, clay layer, brackish water, clay layer and fresh-water bearing zone of appreciable thicknesses at depths of 137 to 182 meter at six locations and from 370 to 430 meter for other two locations under confined conditions. The result of VES studies significantly correspond with the borehole litholog and well log data. A litho-resistivity relationship is established for this area of investigation A Fence diagram is constructed to show the spatial variation of the sub-surface lithology and hydrological characteristics. Chemically the ground water is fresh and mixed cation and anion type as revealed from Piper-Trilinear diagram with TDS ranging from 699 to 1547 mg/l. The geochemical parameters like Total hardness (TH), Sodium absorption ratio (SAR), Soluble sodium percentage (SSP), Percentage of sodium (PS), Kelley’s ratio (KR), Residual sodium carbonate (RSC), Corrosivity ratio (CR), Gibbs ratios (GR), Chloro alkaline indices (CAI), Sea water contamination (SWC) are also calculated for examining the quality of groundwater in the area. The depth of occurrences of freshwater bearing ground water zones for drinking and irrigation purposes are occurring at depths from 137 meter to 430 meter in this area.     

The use of vertical electrical sounding resistivity method for the location of low salinity groundwater for irrigation in Chaj and Rachna Doabs

A geoelectrical resistivity survey using vertical electrical sounding (VES) was conducted at Chaj Doab (land between rivers Jhelum and Chenab, Pakistan) and Rachna Doab (land between rivers Chenab and Ravi, Pakistan), with the objective of investigating groundwater conditions. A total of 90 sites were selected with 43 sites in Chaj and 47 sites in Rachna Doabs. The resistivity meter (ABEM Terrameter SAS 4000, Sweden) was used to collect the VES data by employing a Schlumberger electrode configuration, with half current electrode spacings (AB/2) ranging from 2 to 180 m and the potential electrode (MN) from 1 to 40 m. The field data were interpreted using the Interpex IX1D computer software and the resistivity versus depth models for each location was estimated. The outputs of subsurface layers with resistivities and thickness presented in contour maps and 3-D views by using SURFER software were created. A total of 102 groundwater samples from nearby hydrowells at different depths were collected to develop a correlation between the aquifer resistivity of VES and the electrical conductivity (EC) of the groundwater and to confirm the resulted geophysical resistivity models. From the correlation developed, it was observed that the groundwater salinity in the aquifer may be considered low and so safe for irrigation if resistivity >45 Ω m, and marginally fit for irrigation having resistivity between 25 and 45 Ω m. The study area has resistivities from 3.9 to 2,222 Ω m at the top of the unsaturated layer, between 1.21 and 171 Ω m, in the shallow aquifers, and 0.14–152 Ω m in the deep aquifers of the study area. The results indicate that the quality of groundwater is better near the rivers and in the shallow layers compared to the deep layers.     

Use of vertical electrical soundings to delineate seawater intrusion in a coastal area of Byunsan,Korea

To delineate spatial extent of seawater intrusion in a small experimental watershed in the coastal area of Byunsan, Korea, electrical resistivity surveys with some evaluation core drillings and chemical analysis of groundwaters were conducted. The vertical electrical sounding (VES) method was applied, which is useful to identify variations in electrical characteristics of layered aquifers. The drilling logs identified a three-layered subsurface including reclamation soil, weathered layer and relatively fresh sedimentary bedrock. The upper two layers are the main water-bearing units in this area. A total of 30 electrical sounding curves corresponded mostly to the H type and they were further divided into three classes: highly conductive, intermediate, and low conductive, according to the observed resistivity values of the most conductive weathered layer. In addition, groundwater samples from 15 shallow monitoring wells were analyzed and thus grouped into two types based on HCO₃/Cl and Ca/Na molar ratios with TDS levels, which differentiated groundwaters affected by seawater intrusion from those not or less affected. According to relationships between the three classes of the sounding curves and groundwater chemistry, locations of the monitoring wells with low HCO₃/Cl and Ca/Na ionic ratios coincided with the area showing the highly conductive type curve, while those with the high ratios corresponded to the area showing low conductive curve type. Both the low electrical resistivity and the low ionic ratios indicated effects of seawater intrusion. From this study, it was demonstrated that the VES would be useful to delineate seawater intrusion in coastal areas.     

Groundwater investigation in Kuala Selangor using vertical electrical sounding (VES) surveys

Integrated geoelectrical and hydrochemical surveys were used to investigate and delineate different types of groundwater in the Kuala Selangor alluvial aquifer. Previous hydrogeological borehole investigation showed that this aquifer contains several types of groundwater in relation to its salinity. The high salinity of the groundwater in some areas is believed to be due to either saltwater intrusion from the nearby sea or river infiltration during high tide season. The vertical electrical sounding (VES) method was employed to study and map the subsurface variation of resistivity in the area. For each sounding measurement, a total spread length of 300 m was obtained with a vertical depth penetration of about 60 to 75 m. Chemical analysis of the groundwater samples taken from both shallow and deep boreholes was carried out for the water quality determination. A total of 45 VES stations were succesfully established along three parallel roads with a direction almost perpendicular to the coastal line. The distance between stations varies from 1 to 2 km with a maximum length of about 60 km surveyed line. Results of the vertical electrical soundings as well as the hydrochemistry of the groundwater samples show that the soil and groundwater in the study area can be grouped into fresh and brackish water zones. The subsurface resisitivity sections derived from the VES study suggest that the area is dominated by brackish soil and groundwater zones, especially in the area towards the coast. This result appears to agree well with the groundwater pumped from boreholes scattered around in the area. Water drawn from boreholes near the coast showed higher salinity compared to the water pumped from inland boreholes. Chloride values greater than 250 mg/L are considered to represent the brackish zones whilst values less than 250 mg/L represents zones of fresh soil and groundwater.     

Geoelectrical method in the investigation of groundwater resource and related issues in Ophiolite and Flysch formations of Port Blair, Andaman Island, India

Geoelectrical resistivity investigation using Vertical Electrical Sounding (VES) technique was conducted at Port Blair, South Andaman Island, to locate the fractures in different formations and to decipher its groundwater potential. A total of 40 VES were carried out covering the entire study area using Schlumberger electrode configuration out of which 34 VES fall in Andaman Flysch formations and the remaining VES in Ophiolite formations. The interpreted resistivity results were integrated with nine borehole lithologs for the subsurface analysis. The combination of VES with borehole litholog data has provided a close correspondence on subsurface hydrogeological conditions. The interpreted VES data of various formations showed drastic variations in the resistivity ranging from higher in Ophiolite, moderate in Andaman Flysch and very low in valleys of Andaman Flysch formations. The study further revealed that the weathered and fractured volcanics of Ophiolite groups of rocks and sandstone that occur in the Andaman Flysch formations constitute the productive water bearing zones categorized as good groundwater potential zone. Based on the geoelectrical parameters, viz., thickness of layers and the layer resistivity values, a groundwater potential map was prepared, in which good, moderate, and poor groundwater zones were demarcated. Further, numerical, spatial and litho-geoelectric models of resistivity were analyzed in terms of groundwater potential and these models have thus enabled to prepare a comprehensive groundwater development and management plans proving its efficacy in this art of exploratory investigations.     

Delineation of shallow resistivity structure in the city of Burdur,SW Turkey by vertical electrical sounding measurements

The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and 2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface. The study area is characterized by low resistivity distribution (<150 Ωm) originating from high fluid content in the subsurface. Lower resistivity (3–30 Ωm) is associated with the Quaternary and the Tertiary lacustrine sediments while relatively high resistivity (40–150 Ωm) is related to the Quaternary alluvial cone deposits. This study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area was characterized by high liquefaction hazard risk.     

Geoelectric resistivity sounding of riverside alluvial aquifer in an agricultural area at Buyeo,Geum River watershed,Korea: an application to groundwater contamination study

Twenty profiles of vertical electric soundings (VES) were obtained in a riverside alluvium at the Buyeo area, South Korea, to examine the variations of subsurface geology and associated groundwater chemistry. The combination of the VES data with the borehole data provided useful information on subsurface hydrogeologic conditions. The vestige of an ancient river channel (e.g. oxbow lake) was identified on the resistivity profiles by the lateral continuation of a near-surface perched aquifer parallel to the river. Such a perched aquifer is typically developed in the area with a clay-rich silty surface alluvium which prohibits the infiltration of oxygen. Therefore, groundwater below the oxbow lake shows a very low nitrate concentration and Eh values under the strong anoxic condition. The distribution of water resistivity is correlated with that of measured total dissolved solids concentration in groundwater, while the earth resistivity of the aquifer shows a significant spatial variation. It is interpreted that the earth resistivity of the aquifer is mainly controlled by the soil type rather than by the water chemistry in the study area.     

Geophysical and hydrological investigations at the west bank of Nile River (Luxor, Egypt)

Luxor, the modern Egyptian city that occupies the site of ancient Thebes, is famed for its magnificent ancient monuments. Since 1967, the Aswan high dam has prevented the annual flooding of the Nile River, resulting in excessive salt accumulation on the Nile floodplains and on exposed monument surfaces. In addition, the expansion of agricultural land within the Luxor study area has resulted in increased salinity and groundwater level. These conditions accelerate the degradation of buried and exposed monuments that were fairly well preserved in the past. To mitigate this problem, it is necessary to first understand the near-surface setting and the groundwater conditions of the Luxor area. A geophysical investigation was carried out using resistivity and electromagnetic surveys. In addition, a chemical analysis was conducted of some surface water samples collected from canals and the sacred lake of Memnon Temple. Based on the results of the geophysical surveys and the chemical analysis of the water samples, the shallow subsurface was characterized into four geoelecterical units. Groundwater flow directions were determined to be from the central area to the west, causing a rise in the groundwater levels and groundwater salinity in the area of monuments.     

Integration of geoelectric and hydrochemical approaches for delineation of groundwater potential zones in alluvial aquifer

Geoelectric and hydrochemical approaches are employed to delineate the ground-water potential zones in District Okara, a part of Bari Doab, Punjab, Pakistan. Sixty-seven VES surveys are conducted with the Electrical Resistivity Meter. The resultant resistivity verses depth model for each site is estimated using computer-based software IX1D. Aquifer thickness maps and interpreted resistivity maps were generated from interpreted VES results. Dar-Zarrouk parameters, transverse resistance (TR), longitudinal conductance (SL) and anisotropy (λ) were also calculated from resistivity data to delineate the potential zones of aquifer. 70% of SL value is ≤3S, 30% of SL value is > 3S. According to SL and TR values, the whole area is divided into three potential zones, high, medium and low potential zones. The spatial distribution maps show that north, south and central parts of study area are marked as good potential aquifer zones. Longitudinal conductance values are further utilized to determine aquifer protective capacity of area. The whole area is characterized by moderate to good and up to some extent very good aquifer protective area on the basis of SL values. The groundwater samples from sixty-seven installed tube wells are collected for hydro-chemical analysis. The electrical conductivity values are determined. Correlation is then developed between the EC (μS/cm) of groundwater samples vs. interpreted aquifer resistivity showing R2 value 0.90.     

基于遥感的辽西朝阳地区水文地质信息提取及其应用

为解决辽西地区干旱缺水问题,通过卫星遥感与地面物探相结合的工作方式,研究了水文地质信息提取方法及其应用技术,并在辽西地区开展了初步应用。结果表明,卫星遥感技术不仅可以从宏观上掌握研究区地下水赋存规律,还可探测到常规方法难以发现的水文地质信息,通过卫星遥感技术可以缩小地面物探工作区的范围,该方法有效提高了地下水探测的工作效率及其准确性。此外,通过对电测深电阻率值的定量分析表明,当探测到的九佛堂组岩组电阻率介于18～22Ω·m之间时,该处富水的可能性极大,该方法可有效降低在九佛堂组中物探找水工作的难度。     

Determination of groundwater potential by using geoelectrical method and petrographic analysis in Rawalakot and adjacent areas of Azad Kashmir,sub-Himalayas,Pakistan

The current study is carried out for the determination of groundwater potential in District Rawalakot Azad Jammu and Kashmir (AJ&K) Pakistan by using electrical resistivity method and petrographic analysis of the area. The tape-compass-clinometers method was used in section measurement to understand the facies and depositional environment. The electrical resistivity survey was carried out in the project area in sub-Himalayan Siwaliks system of Pakistan to overcome water scarcity in a few regions. The area was chartered with the Schlumberger configuration up to the AB/2 depth of 150 m. The ABEM Terrameter SAS 4000 (Sweden) and accessories were used to acquire vertical electrical soundings in 24 locations. The results obtained through the 2D and 3D isoresistivity maps of apparent resistivity for 15, 45, and 130 m spacings, the 3D isoresistivity maps of transverse resistance and anisotropy, the VES curve types, and the measured stratigraphic section of surface rocks revealed the confined or semi-confined type aquifers within sedimentary formations. The petrographic analysis indicates the clues of the secondary porosity and fluid migrations through the rocks.     

Joint Russian-American hydrogeological-geochemical studies of the Karachai-Mishelyak system, South Urals, Russia

 In September 1994, a Russian-American team conducted hydrogeological, geochemical, geophysical, and radiometric measurements in the territory of the Mayak Production Association, Russia. The primary purpose of these operations was to examine the frontal area of a radioelement- and nitrate-laden groundwater plume moving from the disposal site, Lake Karachai, toward the Mishelyak River. Activities encompassed (1) isolation of hydrologic intervals in two wells and production of water from these intervals, to compare isolated versus open-well sampling methods and to determine hydraulic transmissivities of the aquifer(s); (2) surface and soil-water sampling, accompanying radiometric measurements and subsequent chemical analyses; and (3) electrical resistivity profiling in areas of expected contrasting resistivity. Preliminary results indicate that (1) ⁶⁰Co, ¹³⁷Cs, and ⁹⁰Sr are present in small concentrations (∼0.1% of permissible levels) in water of the Mishelyak River; (2) analyses of water samples collected by a downhole sampler and of water produced from packed-off intervals agree within limits of laboratory accuracy, attesting to the efficacy of the sampling methods presently used by the Russian workers; (3) considerable differences in contaminant concentrations exist between nearby wells, supporting the concept that the plume from Lake Karachai toward the Mishelyak River is controlled by steeply dipping fractures and shear zones; and (4) strong contrasts occur between the electrical resistivities of soil and bedrock. Further collaborative work is strongly recommended and should include more detailed isolation of intervals in wells by multi-packer installations, to better determine the geochemical and hydrological characteristics of the Karachai-Mishelyak system; deployment of a broader soil water and soil sampling array; a more detailed examination of the distribution and concentration of radionuclides by high-resolution field gamma spectrometry; and a detailing of the area's electrical resistivity setting, using a mobile electromagnetic measurement system. Received: 22 January 1996 · Accepted: 1 April 1996