Evaluation of Lithological Effect on Aquifer Transmissivity and Conductivity in Parts of Rivers State, Nigeria using Vertical Electrical Sounding (VES)

Vertical Electrical Sounding (VES) was used to evaluate the effect of lithology on aquifer transmissivity and conductivity in parts of Rivers State, Nigeria. A total of 10 Vertical Electrical Sounding were conducted at ten locations. The VES data were collected using ABEM terrameter SAS 300B and processed using Win-Resist Software and Microsoft Excel Sheet. The effect of the lithology on aquifer transmissivity and conductivity were analyzed. Result from the Vertical Electrical Sounding revealed a four to six geoelectric layers. The aquifer resistivity values range from 39.40Ωm to 17290.7Ωm. Results of the aquifer conductivity values range from 0.005 to 2.538cm/s with the highest value dominating in the central part of the study area suggesting large grain sands that can permeate groundwater flow while the transmissivity values range from 0.22587cm/s2 to 132.487 cm/s2 with average of 19.1587cm/s2. Area with high transmissivity is identified with high groundwater potential permeable with groundwater flow is seen in the central part of the study area with range of 110 to 135 cm/s2 indicating a thick sandy aquifer. Result from the nearby borehole in correlation with the VES point showed an agreement with the VES data at Ogale Eleme and Elelenwo location. The result of the study can be applied in ground water resources management, hydrological studies and provides valuable information for town planner.

Hydrogeophysical Implication of Geoelectric Sounding at Igarra Comprehensive High School, Akoko Edo Local Government, Nigeria

Electrical resistivity method was used to carry out hydrogeophysical study in order to evaluate the groundwater potential of Igarra Comprehensive High School, Akoko Edo Local Government, Nigeria. The vertical electrical sounding technique (VES) was adopted for the resistivity method. A total of eighteen electrical soundings were conducted across the area using the Schlumberger electrode array with AB/2 varying from 1 to 65 m. After the data acquisition, interpretation was carried out qualitatively and quantitatively and the results were presented as sounding curves, tables, charts, maps and geoelectric sections. The generated geoelectric layers from the sounding curves revealed four geologic layers: the topsoil, the weathered layer, the partially weathered/fractured basement and the fresh basement with their resistivity values ranging from 129.1 to 956.4 -m, 6.8 to 1491.1 -m, 261.3 to 776.6 -m and 1515.6 to 2653.5 -m respectively. The overburden thickness in the study area varies from 5.5 to 23.5 m. The groundwater potential map enabled in the classification of the study area into: low, medium and high groundwater potential area. About 85% of the study area falls within the low groundwater potential rating while about 10% constitutes the medium groundwater potential rating and the remaining 5% constitutes high groundwater potential rating. Keywords: Groundwater, overburden, electrical resistivity, basement, geoelectric sounding.

Groundwater Potential Assessment Using Vertical Electrical Sounding and Magnetic Methods: A Case of Adilo Catchment, South Nations, Nationalities and Peoples Regional Government, Ethiopia

Vertical electrical sounding and magnetic methods were carried out to assess groundwater potential in Adilo catchment, Kembata Tembaro Zone, South Nations, Nationalities and Peoples Regional Government, Main Ethiopian Rift. The data were acquired from eight VES points using Schlumberger electrode arrays with maximum half current electrode spacing ( AB / 2 = 500 ) and 253 magnetic data points were analyzed. The qualitative analysis of VES data was accomplished by using curves, apparent resistivity, and pseudodepths, and the quantitative interpretations of the VES data were constructed by the VES data using IPI-Res3, IPI2Win, and surfer software and constructing geoelectric section along with profiles and lithological information from the borehole and Geosoft interpretation was used for magnetic data. The VES results of the data revealed five geoelectric layers which differ in degree of fracturing, weathering, and formation. The upward continued magnetic field map anomaly to 560 m illustrated northwestern to the southwest; areas have a low magnetic anomaly. Examining the potential aquifer of profile one’s geoelectric section, the horizons of layer four were better potential aquifers as the highly fractured and weathered ignimbrite zone of layer five of VES13 was 219 m deeper than the depths of the other VES points, and along with profile two geoelectric sections, the horizon of layer four VES23 layer five has the lowest resistivity with large thickness at a depth of 253 m. Thus, the low resistivity and the large thickness of these formations are an indication of the high yield of groundwater potential in the study area.

INTEGRATED GEOPHYSICAL MAPPING OF GROUNDWATER AQUIFER FOR SPATIAL DISTRIBUTION OF GROUNDWATER DEVELOPMENT IN IPERINDO AND ITS ENVIRONS, SOUTHWESTERN NIGERIA

Assessment of groundwater potential of Iperindo area, Southwestern Nigeria was conducted by mapping spatial distribution of groundwater availability within the area and consequently locating areas of groundwater reserve to serve the community and its environs. This was achieved by integrating geophysical techniques involving landsat ETM-7 satellite data, aeromagnetic data, VLF-EM and electrical resistivity methods to delineate subsurface structures, understand the direction of groundwater flow, and detect the depth to groundwater aquifer. The result of landsat and aeromagnetic revealed some lineament intersection approximately NE-SW direction and interpreted to be potential sites for groundwater development. VLF-EM revealed geologic structures of significant hydrogeological importance at depths of 40 m to 200 m. Vertical electrical sounding (VES) confirmed high groundwater prospect in the areas with estimated depth to water table between 30 m and 100 m. The integrated results of the study revealed adequate groundwater spatial distribution for effective groundwater development in the area.

GEOTECHNICAL INVESTIGATION OF THE PROPOSED IFE DAM SITE AT KAJOLA VILLAGE, ILE-IFE, SOUTHWESTERN NIGERIA

Geological and geophysical investigations were conducted to assess the competence and structural integrity of the foundation site of the proposed Ife-dam at Kajola Village, Ile-Ife, Southwestern Nigeria. Geological investigation along the two (2) proposed dam axes revealed that the overburden material is loose to dense with angular shearing resistance (ɸ) of 27o to 41o. The soils are predominantly elastic silts; cohesive with considerable strength and stability. Geophysical investigation involving the Schlumberger Vertical Electrical Sounding delineated four (4) lithologies namely: topsoil with resistivity of 69 – 558 Ωm and thickness between 1.5 and 4.0 m; weathered sandy layer with resistivity from 123 – 586 Ωm and thickness between 6.5 and 20.4 m; partially weathered/ fractured basement with resistivity from 60 – 220 Ωm and thickness between 6.5 and 14.0 m; and the fresh basement rock with resistivity from 1337 – 10683 Ωm. There are indications of fractures at a depth of 32 m beneath Axis B extending to Axis A at a depth of 35 m. The subsurface materials are suitable to host a dam. Axis B is more appropriate for the dam axis, although the fracture zone should be factored into the design of the dam to prevent water seepage.

Integrated Ground Penetrating Radar and Electrical Resistivity Study to Explore Such Basrah Low Resistivity Soils for Engineering Purposes, Southern Iraq

A total of 45 ground penetrating radar profiles have been conducted in Basrah City, Southern Iraq, to detect buried utilities in such soils which have not been tested before. This study tries to explore how much this technique can be useful for Basrah low resistivity soils during arid and humid seasons. In Basrah University Campus (silty clay soil) and Basrah Sport City (silty sand soil), 37 and 8 ground penetrating radar profiles were achieved inside these locations respectively. Vertical electrical sounding (Schlumberger array) and electrical profiling (Wenner array) were also used in compatibility with radar surveys side by side in all sites. Here, radargrams do not reveal much more details about the subsurface conditions because of the moisture content and soil characterizations. The actual penetrating depth of 250 and 500 MHz antennas are limited to 1.4 and 0.4 m respectively due to the soil total dissolved solids of about 6790 ppm. The tests suggest that the 250 MHz antenna is somewhat better than the 500 MHz one for detecting the shapes and depths of the buried bodies in silty clay soils during rainy or even arid periods. In Basrah Sport City (500 MHz) antenna, the radargram wave signals are not good for more than 2.5 m depth, and this antenna, rather than the 250 MHZ one is suitable for silty sand soil type.

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.

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.