Hydrogeophysical Study Of The Groundwater Potential Of Ilara-Mokin Southwestern Nigeria

Geoelectric study of the groundwater potential of Ilara-Mokin in Ondo State Southwestern Nigeria was carried out using electrical resistivity (Vertical Electrical Sounding) method with the view to providing adequate information on the different sub-surface geoelectric layers, structural configuration of the concealed basement rocks and the groundwaterpotential of the study area. Forty-one Schlumberger vertical electrical soundings (VES) were conducted across the study area. The computerassisted VES data interpretation enabled generation of geoelectric curves, sections and overburden thickness map which were used in the delineation of key hydrogeologic features like the topsoil, weathered basement, fractured basement and the fresh basement. Resistivity values range from 21 Ω-m to 798 Ω-m in the topsoil, 14 Ω-m to 209 Ω- m in the weathered basement, 51 Ω-m to 209 in the partially weathered/fractured basement and 312 Ω-m to ∞ within the fresh basement. Layer thickness values also vary from 0.3 m to 6.1 m in the topsoil and 0.9 m to 28.6 m in theweathered basement. The depth to the resistive bedrock ranges from 0.3 m to 29.3 m across the study area. The study revealed that greater part of Ilara-Mokin town is underlain by marginally thick overburden thus constituting shallow aquifer units with poor to marginal groundwater potential. Partially weathered/fractured basement were delineated in isolated cases with tendency for low to marginal groundwater yield around central and northeastern areas of the town. The results reasonably provide basic information that is expected to assist in the future development of groundwater resources in Ilara-Mokin

Geophysical study of saline water intrusion in Lagos municipality

Saline water intrusion presently constitutes serious concerns in the Lagos municipality just like many other coastal cities, thus necessitating its intervallic study. The present study involving 52 borehole logs (consisting of natural gamma and electrical resistivity components) was aimed at delineating intruded and vulnerable zones. Saline water columns defined by low resistivity values in the range of 0.1 and 20 Ωm as compared to fresh water (≥ 100 Ωm) were delineated on 22 logs. Four of the geosections generated in this study indicate saline water intrusion at depths varying from surface in Satellite Town, Kirikiri, Ijora, Iganmu, Apapa, Lagos Island, Ikoyi, Victoria Island and Lekki to depths ranging from 40 m at Iganmu to 158 m at Lekki. Intrusions of 47 m (143 - 190 m) and 60 m (56 - 116 m) were delineated at Ajah; 50 m (265 - 315 and 258 - 308) at Lakowe; 57 and 112 m (51 - 108 m and 198 - 308) at Ibeju Lekki, Akodo and 122 m at (233 - 355m) at Awoyaya. The hydrogeologic importance of the Coastal Plain Sand aquifer unit in Lagos is under severe threat of continued sea water intrusion on its southern flank. This study illustrates the current extension of the sea water intrusion. It highlights the depreciation of the water resource due to over pumping at higher rate than the natural recharge and slow sea level rise.Key words: Borehole logs, saline water intrusion/incursion, natural gamma, resistivity, freshwater sand

Terrain And Laboratory Conductivity Studies Of Flood Plains Of Oluwatuyi/Oshinle Areas Of Akure

A shallow electromagnetic study (electrical conductivity and magnetic susceptibility measurements) and laboratory conductivity sampling of the flood plains of Oluwatuyi/Oshinle area of Akure have been undertaken. This is with the aim of correlating the terrain conductivity mapping with laboratory measurements to establish the effectiveness of the induced secondary currents in determining the effects of infiltrating leachates occasioned by heaps of refuse dumped in the course of River Elegbin in the study area. Quadrature and in-phase measurements in vertical and horizontal dipole modes were undertaken on seventeen traverses of various lengths. Laboratory conductivity measurements were conducted on twenty one water samples obtained from hand-dug wells.The horizontal dipole measurements exhibit higher conductivity values suggesting contamination of the upper strata from the ubiquitous refuse in the area. The lower conductivity values obtained from the vertical dipole mode may be due to the high retarding capability of abundant clay in the area to contaminant flow. The similarity in conductivity distribution obtained from field and laboratory studies show that terrain conductivity is strongly influenced by saturating fluid.The high magnetic susceptibility values obtained in northern course of the river suggests predominantly ferromagnetic dumps while the low values characterizing the central and southern course indicate predominantly domestic waste in the zone

Hydrogeophysical study of Ogbese South Western Nigeria

No Abstract.Global Journal of Pure and Applied Sciences Vol. 13 (1) 2007: pp. 55-6