On the scope and limitations of the electromagnetic method in groundwater prospecting in a Precambrian basement terrain - a Nigerian case study

Olorunfem, M.O.; Dan-Hassan, M. A.; Ojo, John Sunday

doi:10.1016/0899-5362(95)00033-p

Cited by 13 publications

(8 citation statements)

References 3 publications

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“…The electrical resistivity method involving 1D Vertical Electrical Sounding (VES) is commonly used to identify aquifers in basement complex environment (Ako and Olorunfemi, 1989;Olorunfemi and Okhue, 1992;Olayinka and Olorunfemi, 1992;Olorunfemi and Fasuyi, 1993;Ademilua and Olorunfemi, 2000;Bayode et al, 2006 andBayowa et al, 2014). At times, the VES techniques is preceded by horizontal profiling or electromagnetic profiling as a reconnaissance technique to map areas with thick weathered layer (overburden) and or discontinuities created by faults and fractured zones while the VES is adopted as a confir mator y technique (Olorunniwo and Olorunfemi, 1987;Hazell et al, 1988;Hazell et al, 1992;Olorunfemi et al, 1995;Afolayan et al, 2004;Oloruunfemi et al, 2005and Sharma and Baranwal, 2005and Okafor and Mamah, 2012. The VES and the horizontal profiling techniques are 1D data gathering for measurement of variations in resistivity or electromagnetic response along vertical and horizontal directions respectively.…”

Section: Integrated Geophysical Methods and Techniques For Siting Promentioning

confidence: 99%

Integrated geophysical methods and techniques for siting productive boreholes in basement complex terrain of southwestern Nigeria

Olorunfemi¹,

Oni²

2019

Ife Journal of Science

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Electrical resistivity survey involving 2D Dipole-Dipole subsurface imaging and 1D Vertical Electrical Sounding (VES) and an integrated magnetic and electrical resistivity survey involving magnetic profiling and 1D VES/2D electrical imaging techniques were carried out at two sites underlain by grey gneiss and pegmatised schist, respectively, within the Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria. The surveys were carried out with a view to delineating the subsurface layers and determining the geoelectrical characteristics; identify geological structures such as faults, fractured, jointed and sheared basement zones that are favourable to groundwater accumulation and transmission and estimate hydrogeologically significant borehole drill depth in an area with previous experience of failed borehole drilling attempts. At the two sites (A&B) investigated, the 2D resistivity images identified suspected fractured basement zones as low resistivity vertical discontinuities within high resistivity fresh basement host rock. The magnetic profiles at site B displayed typical magnetic anomaly of a thick dyke (two magnetic lows with central high in low magnetic latitude) over each vertical resistivity discontinuity. The follow-up VES delineated maximum of five subsurface layers which include the topsoil/laterite, weathered layer, partly weathered/fresh basement, fractured basement and the fresh basement. The weathered/fractured basement constitutes the main aquifer unit with thicknesses varying from 17.7-125 m. Two boreholes, one per site, were drilled to 80 m at site A and 70 m at site B. Both boreholes encountered the predicted fractured basement zones and the borehole logs correlated well with the interpretation models of the drilled VES locations. The boreholes were very productive (yields of about 1.5 l/s and 2.2 l/s at sites A & B respectively). The study demonstrated the effectiveness of integrated geophysical methods and techniques in providing information on the subsurface sequence and the structural disposition required for a successful groundwater development through borehole drilling, in a borehole-failure-prone basement complex terrain.

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Section: Integrated Geophysical Methods and Techniques For Siting Promentioning

confidence: 99%

Integrated geophysical methods and techniques for siting productive boreholes in basement complex terrain of southwestern Nigeria

Olorunfemi¹,

Oni²

2019

Ife Journal of Science

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“…Such targets as displayed in Fig 2 below are characterized by peak positive amplitude filtered real and Sshaped anomaly whose inflexion point lies directly above the vertically dipping fractured zone and a high amplitude EM response with a negative polarity. A combination of the above EM characteristics is a strong indication of the presence of a conductive near vertical fractured zone or lithological contact or interface and a conductive overburden respectively (Olorunfemi et al, 1995).…”

Section: Methodsmentioning

confidence: 99%

“…Electromagnetic method also constitutes the most reliable means, outside direct mechanical drilling, through which basement structures such as ancient river channels, basement depressions and fractured zones that are of hydrogeological significance can be mapped (Eaton and Watkins, 1970;Vanderberghe, 1982). EM response in basement complex area as observed by Olorunfemi et al, 1995, is strongly influenced by the conductive weathered zone. A very conductive weathered layer will give high amplitude EM response with usually negative polarity.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic Geophysical Prospecting For Groundwater in Basement Complex Terrain: A Case Study of Ola-Oluwa Area of Osun State, Southwestern Nigeria.

Onimisi¹,

Ayuba²,

Daniel³

2014

IOSRJAGG

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Electromagnetic (EM) survey involving horizontal profiling using ABEM WADI VLF equipment has been employed in prospecting for groundwater occurrence in the Basement complex terrain of Ola-Oluwa local government area of Osun state, southwestern, Nigeria. The qualitative interpretation of the EM data obtained from the survey shows that the amplitude of the filtered and actual real EM anomalies in the study area varies from-79.1% to +0.8% and-2.4% to-37.9% respectively in Ajagba Locality,-26.9% to 47.1% and-42.6% t0-55.4% respectively in Asa locality,-27.9% to-37.0% and-23.3% to 39.0% respectively in Ikonifin locality,-2.1% to 69.8% and-21.5% to-64.5% in Ikire-Ile respectively, In Baramolu locality, the EM readings in most of the recording stations could not be recorded due to high noise level (possibly from the over head power cables) overriding the EM signals. The EM anomalies in the few stations recorded in this locality vary from-0.2% to 44% and-0.3 to 48% respectively. The EM anomalies in all the localities in the study area are generally negative and devoid of any significant peak positive filtered real anomaly typical of subsurface structure. The typically negative EM amplitude anomalies observed in the study area are diagnostic of conductive overburden. The aquifer potential in the study area is generally poor as accumulation of groundwater will be restricted to the overburden layer since the underlying basement layer is generally devoid of subsurface structure.

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“…However, these methods of groundwater investigation are neither cost nor time effective and also often require skilled personnel (Moss, ; Fetter, ; Mukherjee et al ., ). Geophysical investigation techniques have also been used by various researchers to explore groundwater resource in different geological units (Amadi and Nurudeen, ; Olorunfemi et al ., ; Olayinka and Olayiwola, ; Adiat et al ., ; Mukherjee, ). However, because of the lack of precision of in situ data analysis, results and interpretations of geophysical surveys are always required to be validated by borehole data (Shashtri, ).…”

Section: Introductionmentioning

confidence: 99%

Geospatial and geostatistical approach for groundwater potential zone delineation

Mallick

Singh

Al-Wadi

et al. 2014

Hydrological Processes

144

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Over the past few decades, groundwater has become an essential commodity owing to increased demand as a result of growing population, industrialization, urbanization and so on. The water supply situation is expected to become more severe in the future because of continued unsustainable water use and projected change in hydrometeorological parameters due to climate change. This study is based on the integrated approach of remote sensing, geographical information system and multicriteria decision‐making techniques to determine the most important contributing factors that affect the groundwater resources and to delineate the groundwater potential zones. Ten thematic layers, namely, geomorphology, geology, soil, topographic elevation (digital elevation model), land use/land cover, drainage density, lineament density, proximity of surface water bodies, surface temperature and post‐monsoon groundwater depth, were considered for the present study. These thematic layers were selected for groundwater prospecting based on the literature; discussion with the experts of the Central Ground Water Board, Government of India; field observations; geophysical investigation; and multivariate techniques. The thematic layers and their features were assigned suitable weights on Saaty's scale according to their relative significance for groundwater occurrence. The assigned weights of the layers and their features were normalized by using the analytic hierarchy process and eigenvector method. Finally, the selected thematic maps were integrated using a weighted linear combination method to create the final groundwater potential zone map. The final output map shows different zones of groundwater potential, namely, very good (16%), good (35%), moderate (28%) low (17%) and very low (2.1%). The groundwater potential zone map was finally validated using the discharge and groundwater depth data from 28 and 98 pumping wells, respectively, which showed good correlation. Copyright © 2014 John Wiley & Sons, Ltd.

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On the scope and limitations of the electromagnetic method in groundwater prospecting in a Precambrian basement terrain - a Nigerian case study

Cited by 13 publications

References 3 publications

Integrated geophysical methods and techniques for siting productive boreholes in basement complex terrain of southwestern Nigeria

Integrated geophysical methods and techniques for siting productive boreholes in basement complex terrain of southwestern Nigeria

Electromagnetic Geophysical Prospecting For Groundwater in Basement Complex Terrain: A Case Study of Ola-Oluwa Area of Osun State, Southwestern Nigeria.

Geospatial and geostatistical approach for groundwater potential zone delineation

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