Browsing by Author "Ojulari, BA"

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    ELECTRICAL ASSESSMENT OF AQUIFERS IN THE BASEMENT COMPLEX OF UNILORIN: IMPLICATIONS FOR EXISTING BOREHOLES
    (School of Science and Technology Education, Federal University of Technology, Minna, 2015) Olatunji, S; Ojulari, BA
    Schlumberger 4-electrode array was employed to sound 21 stations. IPI2WIN and Surfer12 software were used to infer lithological series, aquifer thickness, and depth. The aquifer hydraulic conductivity K and transmissivity T were calculated from the VES data using the Dar Zarouk principles. The field curves show that the area has 3 and 4 geo-electric layers. The layers were interpreted as the topsoil (130- 1469 Ωm), clayey (wet to dry) (52.6 – 8552 Ωm), weathered/fractured basement (46.2- 249 Ωm), and fresh basement (454- 5022 Ωm) respectively. The aquiferous zones lie within the second and third layers. The aquifer depth is between 6.17 m and 24.9 m while the thickness ranges from 1.89 to 22.7 m. The longitudinal conductance S ranges from 0.02 to 0.468 Ω-1 and transmissivity T varies from 246 to 2419.8 Ωm2. The results confirmed the functionality of boreholes, such as VES3, sited in areas with maximum aquifers and highest transmissivity T. The NE and NW parts were found most suitable for freshwater exploitations. Low longitudinal conductance which implies low protective cover, in the vicinity of the borehole near VES 6 suggests the contamination claim of its water.
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    Monitoring of Seepage in Agba Dam, Kwara State, Nigeria, Using Vertical Electrical Sounding Technique
    (School of Engineering and Engineering Technology, Federal University of Technology Minna, 2015) Olatunji, S; Ojulari, BA; Abubakar, HO; Yusuf, MA
    The geophysical investigation has been undertaken at Agba Dam, Ilorin; located around the southern flanks of the Nigeria basement complex. It is bounded by longitudinal E 0040 35’ 0.72” – E 0040 35’ 40.6” and latitude N 080 28’ 23.3” – N 080 28’ 40.1”. This was aimed at investigating possible seepage along the dam’s flank. The vertical Electrical Sounding (VES) technique was used for the field study. Twenty VES stations of four profiles were established along the bank of the dam and data were acquired using the Schlumberger electrode configuration. The resistivity values in the surveyed area vary from 9.28 Ωm to 9409.37 Ωm. Three major geo-electric layers were delineated which are: topsoil, weathered layers, and fresh basement. The 2D pseudo-section along the profiles revealed the lowest resistivity of 30 Ωm at the depth of 3m. This observation could be a signature of seepages around those areas. Also, a minor conductive zone that appears close to the dam embankment could signify inceptions of buried erosion. This could be inimical to the future sustenance of the dam. The highest resistivity of 1000 Ωm was discovered at the depth of 10 m around VES 13 which is the area of the Dam embankment. This implies that the structure of the Dam embankment is not compromised and is still effective.