In this research, groundwater yield of Ibodi and its environs have been investigated using hydrogeologic data and vertical electrical sounding. The study was carried out with a view to providing information on the geoelectric characteristic of the subsurface sequence, bedrock topography, subsurface structural features and their hydrogeologic significance, in order to determine possible areas for groundwater yield zones. The study involved the use of Schlumberger vertical electrical sounding data at sixty-eight (68) stations. The results from depth sounding data interpretation revealed four subsurface geoelectric layers namely; the topsoil, weathered layer, fractured basement and the fresh basement The weathered layer and fractured basement constitutes the aquifer units with varying thickness. The second order parameters were determined from the interpretation of vertical electrical sounding results and used to determine the groundwater yield index value (G.W.Y.I) by multiplying the coefficient of anisotropy (λ) and total transverse resistance (T) i.e. (λ*T). The groundwater yield index value was used to model the groundwater Original Research Article

Vertical Electrical Sounding (VES) surveys were carried out at Ajagba, Asa and Ikonifin communities in the north of Ola Oluwa local government area of Osun state, Nigeria in order to delineate the geoelectric layers in the area as well as evaluate the groundwater potential. The area is in the basement complex terrain of Nigeria where the occurrence of groundwater is highly unpredictable and hence requires the use of hydrologic, geophysical and geologic surveys to achieve success in groundwater development programs. The survey delineated a maximum of four geoelectric layers which may be interpreted to correspond to four geologic layers viz the topsoil, weathered basement, partly weathered/fractured basement and the fresh basement. The weathered basement and the partly weathered/fractured basement layers constitute the aquifer units. The partly weathered/fractured layer is significant in enhancing the ground water potential in this area because of its relatively low resistivity resulting from its high fracture frequency. The ground water potential in the area varies from medium to high. Groundwater development is therefore feasible in these communities.

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.