Geophysical Investigation For Groundwater Potential Evaluation Of A Regolith Aquifer In A Typical Basement Complex Terrain; A Case Study Of Ikole Ekiti, Southwestern, Nigeria.

ABSTRACT

A geophysical investigation involving the electrical resistivity method was carried out at

IkoleEkiti of South Western, Nigeria with the main aim of investigating the area for

groundwater potential of the regolith aquifer.

The objectives are to identify geological structures and aquifers favorable to groundwater

accumulation andalso input geoelectric layers parameters into a software to produce maps of

the subsurface in order todetermine the groundwater potential of the regolith aquifer.

Thirty (30) Vertical Electrical Soundings (VES) using the Schlumberger array with

maximum electrode separation AB/2 of 100m was carried out with ABEM SAS-300

Resistivity Meter. The VES data were presented as sounding curves and interpreted

quantitatively through the method of partial curve matching and 1-D computer assisted

forward modelling. The sounding curves show three layers tofour layers earth models. The

three layer curve are characterized by H and A type which represents altogether about 54%

of the curve types in the study while the four layer models are characterized by KH, KQ,

QH and AH which altogether covers about 46% of the curve type in the study area. The

overburden was assumed to include the topsoil, upper and lower saprolite, saprock, and

weathered basement. The weathered basement is the aquifer type delineated for the area. Groundwater potential

was evaluated from the maps (i.e. overburden thickness, weathered layer thickness,

weathered layer resistivity,and bedrock relief maps) revealing that the Northeastern,

Eastern and Southeastern parts of the study area are the mostpromising region for borehole

development. However, the western region of the study area can also be considered as fair forborehole development.

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