Evaluation of Groundwater in Udi L.G.A. in Enugu State, Nigeria

Groundwater has remained indispensable in Enugu state Nigeria owing to industrialization, lack of surface water, and significant depth to aquifer in the area. A geophysical investigation involving vertical electrical soundings was conducted in order to evaluate groundwater potential at some locations in the Udi Local Government Area of Enugu State. With the aid of resistivity instrument ABEM Terrameter, four (4) Vertical Electrical Sounding using Schlumberger configuration were conducted, and the data acquired was interpreted using WINRESIST software. Information obtains from the survey shows that the underlying geological formation in those areas has between 5 – 7 layers. The apparent resistivity obtained in all the layers of the locations ranges from 47.1 – 6956.8 Ωm, while the aquifer was interpreted to exist at a depth between 90 – 120m. Result obtained from this geophysical investigation has shown that the survey area possesses a good groundwater potential which will go a long way in cushioning the effect associated with water scarcity in the area if exploited.

Geophysical and Hydrogeological Investigations of Water Leakage from a Reservoir Dam to a Coastal Aquifer: The Lebna Case Study (Northeastern Tunisia)

In semiarid regions, dams are useful for surface water storage, sediment sequestration, and aquifer recharge. Built in 1987 on the Cap Bon peninsula (in northeastern Tunisia), the Lebna Dam is considered a good example of a multifunctional reservoir. The dam feeds two important irrigation networks, stores large sediment quantities, and allows a significant recharge flow to the underlying aquifer. This work suggests new leakage flow and dam-aquifer interaction characterizations through the development of an approach that combines a water balance calculation, geological field observations, groundwater monitoring, and geophysical research. The hydrological balance calculation performed over the 27-year monitoring period, from 1990 to 2017, shows that an estimated water volume of 3.7 Mm3y-1 has leaked from the Lebna reservoir to the coastal aquifer. Geological mapping of the Lebna Dam basin in summer 2019 revealed the existence of permeable layers of sands to sandstones exposed along the southern banks of the reservoir and extending to an elevation that included the water level when the dam is full; these rocks outcrop at approximately 16 m.a.s.l. A geophysical survey based on 67 vertical electrical soundings and 8 electrical resistivity tomography profiles in the area downstream of the reservoir was carried out to identify the lateral continuity of the recharge zones. Piezometric campaigns consisting of four field surveys in 2019 and 2020 were conducted in the region downstream of Lebna Dam, consisting of 71 water well samples. An interpretation of these geophysical data coupled with available borehole logging and piezometric measurements was used to define the leakage geometry from the reservoir dam to the coastal aquifer. The collected evidence led to the conclusion that concentrated recharge occurs in the downstream sections, especially on the right bank of the aquifer.

Microzonification of Floor with Sliding in Nulti Parish

Cuenca is located on three areas controlled by mega faults and 14 areas at risk from landslides. One of them is the Nulti community that registers landslides in 16 subzones during the past 10 years. The waters presence on the ground is one of the causes of these earth movements, and this generated infrastructural and environmental losses. According to the update of the Development and Land Management plan, the Santa Cecilia Pasto Romero neighborhood is one of the affected areas. This community is located in the Parish Center. This place lost a considerable number of houses and equipment like educational, health, religious, administrative infrastructure, because it has landslides of great magnitude. Given these antecedents, we carried out a study that allows to know the behavior of this soil against seismic waves and identify risk areas, their properties such as soil type, allowable loads, and elasticity modulus. In this way, the risks presented by these landslides were determined from a soil profile by processing the results of the Geophysical analysis like seismic refraction tests, standard penetration, and electrical soundings. This study generates future lines of research like slope stabilization and drainage designs. This study opens the possibility of being replicated in the other parishes of Cuenca. The subsoil presents a cohesive material with high plasticity. The soil has deposits with silty clay matrices of high plasticity. This mass of soil has been removed by the effects of landslides and colluvial deposits. Therefore, its low shear wave velocities expose loose soils of high plasticity and medium to high expansivity.

Numerical modeling of fault structures in the Kurai basin of Gorny Altai based on data from direct current methods

The southern site is located in the junction zone of the Southwestern and Eshtykel bench, where vertical electrical soundings were performed, and a preliminary fault-block depth model was built based on the results of field data interpretation using a horizontally layered model. Comparison of geoelectric and seismological data showed that the epicenters of significant earthquakes (M> 4) are concentrated in the identified faults. In the central site, three profiles of electrotomography were made through a bench, well expressed in the relief. Three-dimensional modeling was used to verify and clarify the structural features of both sections. Modeling is performed using programs EMF_DC3Dmod (GPU) - an accelerated version of the program EMF_DC3Dmod for vertical electrical sounding and SCALA-48 (GPU) for the method of electrotomography. The study is relevant for the tasks of geodynamics, seismic zoning and seismic hazard assessment.

Geophysical Delineation of Freshwater–Saline Water Interfaces in Coastal Area of Southwest Bangladesh

Insufficiency of potable water is acute in southwest (SW) coastal areas of Bangladesh. The local population ignores the depth to saltwater/freshwater interface causing many unsuccessful waters wells drilling. In this context, a combined use of borehole logs, geophysical well logs, vertical electrical soundings (VES), electrical resistivity tomography (ERT) and electrical conductivity (EC) of sampled waters was performed to identify saltwater/freshwater interface depths in this coastal part. The study shows that the depth to freshwater/saltwater interface varies from place to place occurring commonly between 190 to 285 m, and locally as shallow as 146 m. The shallow freshwater/saltwater interface depth is greatly influenced by the upconing of fresh water from the deep aquifer (DA) near the major rivers and coast compared to the landward part and is mixed with more saline waters above. Vertically infiltrated saltwater is the main cause of brackish water in the upper shallow aquifer (USA), which is hydraulically connected with the lower shallow aquifer (LSA), and not directly recharged from the Bay of Bengal in the south. The study will contribute to find out the depth of the potential freshwater aquifer and assess the aquifer vulnerability in the coastal area of SW Bangladesh.

Hydrogeophysical Characterization of the Marizal–São Sebastião Aquifer System in the Surroundings of the Limpec Sanitary Landfill, Camaçari, Bahia, Brazil

ABSTRACT. A detailed hydrogeophysical survey was conducted using the geoelectrical method in the surroundings of the LIMPEC sanitary landfill, municipality of Camaçari, Bahia, Brazil. Twenty-six vertical electrical soundings (VESs) were done, configured according to the Schlumberger electrode array and spaced up to 400 m between current electrodes. Hydrogeological quali-quantitative information was obtained by integrating geoelectrical results to data from wells and local geology information, namely: (i) an apparent resistivity map showed the occurrence of a conductivity anomaly, possibly attributed to the contamination plume, dispersed within the saturated zone, and presenting a SSE convection direction; (ii) one-dimensional inversions allowed to interpret the stratigraphic pattern, identify static level depth and the occurrence of possible contamination plumes, and indicate the direction of groundwater flow, which was also towards SSE; (iii) two-dimensional inversions produced inverted geoelectrical profiles, with a mean error below 2%, and confirmed the occurrence of possible contamination plumes disseminated within the unsaturated zone and dispersed within the saturated one. The geoelectrical facies with the highest resistivity values (> 600 ohm.m) were related to the São Sebastião Formation. Facies with intermediate values (100 to 800 ohm.m) regarded the Marizal Formation. In turn, those with the lowest values (< 100 ohm.m) were related to contamination plumes and/or eventual occurrences of silt/clay; (iv) the parameters of porosity, hydraulic conductivity, and transmissivity were estimated between 19.2 and 34.2%, 0.11 and 3.37 x10-3 cm/s, and 4.7 and 145.6 m²/d, respectively; and (v) local free aquifer vulnerability was classified as high, according to the evaluation using the GOD method.Keywords: geoelectrical method, urban solid waste, hydrodynamic parameters. Caracterização Hidrogeofísica do Sistema Aquífero Marizal – São Sebastião, no Entorno do Aterro Sanitário Limpec, Camaçari, Bahia, BrasilRESUMO. Um estudo hidrogeofísico de detalhe, utilizando o método geoelétrico, foi conduzido no entorno do aterro sanitário LIMPEC, município de Camaçari, Bahia, Brasil. Vinte e seis sondagens elétricas verticais (SEVs), sob configuração do arranjo Schlumberger de eletrodos, com espaçamento de até 400 m entre os eletrodos de corrente foram executadas. Informações quali-quantitativas de âmbito hidrogeológico foram alcançadas a partir da integração dos resultados geoelétricos a dados de poços e informações da geologia local, a saber: (i) o mapa de resistividade aparente revelou a ocorrência de uma anomalia condutiva, possivelmente atribuída à pluma de contaminação, dispersa na zona saturada, apresentando sentido de convecção na direção SSE; (ii) as inversões unidimensionais possibilitaram interpretar o padrão estratigráfico, identificar a profundidade do nível estático, a ocorrência de possíveis plumas de contaminação e apontar o sentido do fluxo hídrico subterrâneo também para SSE; (iii) as inversões bidimensionais geraram perfis geoelétricos invertidos, com erro médio inferior a 2%, e confirmaram a ocorrência de possíveis plumas de contaminação disseminadas na zona não saturada e dispersas na zona saturada. Os fácies geoelétricos de maiores valores de resitividade (>600 Ohm.m) estão atribuídos à Formação São Sebastião. Os fácies de valores intermediários (100 a 800 Ohm.m), referem-se à Formação Marizal. Já os de menores valores (<100 Ohm.m), a plumas de contaminação e/ou eventuais ocorrências de silte/argila; (iv) os parâmetros porosidade, condutividade hidráulica e transmissividade foram estimados serem entre 19,2 a 34,2%, 0,11 a 3,37 x10-3 cm/s e 4,7 a 145,6 m²/d, respectivamente; e (v) a vulnerabilidade do aquífero livre local foi classificada como alta, segundo avaliação realizada utilizando o método GOD. Palavras-chave: método geoelétrico, resíduos sólidos urbanos, parâmetros hidrodinâmicos.

Dar Zarrouk Parameters for delineation of groundwater potentials in Ganye and Environs, Adamawa State, Northeastern Nigeria

Groundwater is the main source of water supply in areas in Nigeria including the research area. The research is aimed at delineating groundwater potentials in Ganye and environs using Dar Zarrouk parameters. Fourteen (14) vertical electrical soundings were conducted across the study area in order to determine Dar Zarrouk parameters to determine groundwater potentials in Ganye and environs. The area is underlain by migmatite-gneiss and Pan African granites. Weathered/fractured basement constitute the aquifer type in the area. The aquifer conductivity in the study area range between 0.00871 to 0.032032 ?-1 with mean value of 0.019493 ?-1. The aquifer longitudinal conductance ranges between 0.22246 to 0.759252 with mean value of 0.432846. The transverse resistance range between 627.8721 to 1,857.282 ?m2 with average value of 1,235.854 ?m2. The aquifer hydraulic conductivity range between 6.9314 to 15.562 m/day with mean value of 9.738 m/day while the transmissivity across the study area range between 114.2152 to 378.774 m2/day with mean value of 216.0487 m2/day.

Contribution of Geo-electrical Soundings and Pedological Wells to the Estimation of the Tonnage of Laterite Gravels of the Northwestern Flank of Mount Bangou: Implication in Road Construction.

The increasing demands on lateritic gravels in road construction nowadays make it necessary to quantify the available resources that can be used in road construction. The aim of this study is to estimate the tonnage and to valorize the lateritic gravels of the North flank of Mount Bangou (West, Cameroon) in road construction. Interpretation of 48 vertical electrical soundings coupled with 20 pedological wells from 05 lateritic gravel sites was carried out to determine the thickness of the gravelly horizon. The thickness of the gravelly horizon obtained from the geo-electrical soundings is the highest (8.88 to 12.45 m) compared to that obtained from the pedological wells (1.23 to 1.98 m) and thus shows the inadequacy of the pedological wells for the determination of the thickness of the lateritic gravels. Thus, the electrical resistivity method is appropriate to estimate the thickness of the gravelly horizon. The lateritic gravels studied are characterized by the electrical resistivity curves of type K, HK, Q, QH, KQ, HKH, H and KH. The medium (8 to 36 m) and thick (13 to 44 m) zones are areas of high potential lateritic gravels. The proven reserves of lateritic gravels at the Chenye, Sekakouo, Bamendjou 1, Bamendjou 2 and Bangam sites are respectively 3479 003 t, 1 389 522 t, 5 002 505 t, 839 455 t and 2 663 105 t and can build respectively 539 298 m; 226 167 m; 131574 m; 778314 m and 401068 m of road, either as a form layer or sub-base.

GEOPHYSICAL INVESTIGATION OF GROUNDWATER CONTAMINATION USING DC RESISTIVITY TECHNIQUE AT THE MALE HOSTEL OF ISA KAITA COLLEGE OF EDUCATION DUTSIN-MA, KATSINA STATE, NIGERIA

A geophysical investigation involving Vertical Electrical Sounding (VES) using the Schlumberger array was carried out at the Isa Kaita College of Education specifically at the Male Hostel. The aim of the investigation is to explore the groundwater contamination of the area with the objectives: to determine the depth to basement of the study area, to determine the aquifer thickness, to determine the depth to aquifer, to determine the conductivity of the aquifer and to determine the thickness of topsoil and its variation in resistivity. A total of four (4) vertical electrical soundings were carried out using Schlumberger configuration. Terrameter signal averaging system (SAS) model 300 was the instrument used. The survey area is dominated by mainly four layers, namely: Topsoil, Weathered basement, fractured basement. The value of VES 03 and VES 04 have high electrical conductivities which likely shows they are contaminated, The topsoil resistivity along the profile ranges from approximately 1 to 154, The depth to basement (basement topography) Varies from 4.94 m to 7.59 m, The thickness of aquifer range from 1 m to 6.8 m. Therefore VES 02 has high Potential for groundwater because it has retaining capacity and good aquifer thickness and is therefore recommended for borehole establishment. It is recommended that the management of Isa Kaita College of Education should provide a concrete dumping site to avoid leaching of waste in ground thereby contaminating the groundwater.

Determination of the Spread of Heavy Metal from Ori-Ile Battery Waste Dumpsite Using Electrical Resistivity Method

Contaminants from waste dumpsites have become sources of concern. Disposed wastes (Heavy metal) from battery industries could contaminate soil, agricultural plants, and groundwater. Therefore, this study aimed at the determination of the migration of heavy metal (Lead) from a Battery Waste Dumpsite using the electrical resistivity method. Using Schlumberger array, fifteen (15) Vertical Electrical Soundings (VES) were carried out around a Battery Waste Dumpsite in Ori –Ile, Ikumapaiyi at Olodo community, Ibadan, Oyo State, Nigeria. Preliminary analyses of VES data were performed and were fed into software (WINRESIST 1.0) for qualitative interpretation to reveal apparent resistivity values, the number of layers, and thickness. Three and four layers of topsoil, sandy-clayed, weathered/fractured basement, and basement were obtained. Various values of lowest apparent resistivity and depths of penetration of leached lead on the four sides of the battery waste dumpsite were obtained. The lowest apparent resistivity values obtained were converted to apparent conductivity and plotted against the distance of each VES point. Five collected water samples from available hand-dug wells around the dumpsite were analyzed for the presence of lead using an Atomic Absorption Spectrometer. Graph of apparent conductivity against VES distance indicated a decrease in conductivities with distance, an indication of reduction of Concentration of lead with distance. The level of Lead ranged from 0.081 to 0.770 mg/L which was above the tolerance level of 0.01 mg/L of WHO and SON, an indication of heavy metal pollution in groundwater. This study has established that lead ions were present in groundwater and had spread to a distance of 80 m from the battery waste dumpsite and were more pronounced on the southern region of the dumpsite.