Geoelectric Evaluation Of Groundwater Potentials Of Faculty Of Science And Its Environs, Federal University Oye Ekiti Phase Two, South Western Nigeria

ABSTRACT

A Geophysical integrated research work involving the use of Electrical Resistivity (ER) and the Very Low Frequency Electromagnetic methods (VLF-EM) were carried out for groundwater potential on the Precambrian basement complex terrain of Federal University Oye-Ekiti Phase

two (2), Ekiti-State Southwestern Nigeria. Five traverses running from East to West were established in the study area. The length ranges from 110m to 160m. Five VLF-EM measurements were acquired, while a total of twenty Vertical electrical sounding (VES) stations were occupied within the study area. The VLF- EM responses were interpreted using the Karous Hjelt (KH) package and inverted into its 2D Pseudosection. On the basis of these VLF-EM responses, series of conductors were identified (C1 – C6). The six (6) major conductive zones are suspected to be fractures. The VES data were quantitatively interpreted using the partial curve matching technique and 1-D forward modeling with WinResist 1.0 version software. The VES result also delineated four major Geo-electric layers within the study area. The topsoil,

weathered basement, partly weathered/ fractured basement and fresh basement. The top soil (resistivity varies from 28 to 175 ohm-m and thickness ranges from 0.3 to 3.7 m); weathered basement (resistivity varies from 22 to 498 ohm-m and thickness ranges from 1.3 to 38.7 m),Partly weathered/fractured basement (resistivity varies from 381 ohm-m to 775 ohm-m and thickness ranges from 8.5m to infinity) and bedrock with resistivity 809 to 6693 ohm-m and

depth to bedrock 1.5 to 43 m). The interpreted data revealed A-curve type as the dominant curve type in the study area. It has 55% dominance. Other curve types include the KH (10%), HKH (5%), AA (5%), H (5%), K (5%), AKH (10%) and HA (5%).

Therefore, VES 3, 5, 10 and 15, are thereby classified as good potential zones for groundwater development because of their bedrock relief and depression, thickness and resistivity values.

VES 6, 7, 8 and 9 have low groundwater potentials, while VES 1, 2, 12, 13, 14, and 20 have poor groundwater potentials. Other VES points were not chosen on conductive zone parameters. VES 4, 11, 16, 17, 18 and 19 are partly weathered/ fractured basement and would have been good

points for groundwater prospects if their thicknesses (at the third geoelectric layers for VES 4, 11 and 16, and second geoelectric layers for VES 17, 18 and 19) were known.

The interpretation of the results classifies the area from poor to medium groundwater potential zones

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