Pages: (68-83 )
Abstract
Groundwater exploration was carried out through applicable electrical resistivity investigation with the aim of delineating probable zones of groundwater prospect within the near-surface geological formation in the study area. The dominant rocks in the study area are migmatite gneiss, biotite /biotite-muscovite granite and potassic syenite which falls within the Crystalline Basement Complex of southwestern Nigeria. Forty (40) Resistivity Sounding were explored using Schlumberger arrangement with the current spacing (AB/2) of a hundred metre at purpose by ABEM resistivity meter. The sphere knowledge obtained were analysed quantitatively by iteration package “WINRESIST” and qualitatively by partial curve matching. Bedrock resistivity, longitudinal conductance, reflection co-efficient and overburden thickness, longitudinal conductance parameters were calculated and their plots were prepared also and used for assessing the aquifer prospects. The results show that the subsurface lithology consists generally of three to five layers which are QH. A, KH. K, HKH. H and HA -types resistivity curves mainly. The geo-electric layers display 3–5 horizons viz: the topsoil (34.0-63277.4 Ωm), clayey sand (7.9 -8322.1 Ωm), fractured bedrock (19.9 - 10347Ωm) and the fresh bedrock (55.5 -5461.6 Ωm). The overburden thickness isopach plot showed an overburden thickness varies of 5.0 to 39.5m with values larger than thirty metres within the study space. About 75% of the studied groundwater samples revealed low to medium potential zone, while 15% and 10% revealed high and very- high potential zones respectively. Subsequently, the groundwater potential rating of the study area is viewed as normally low. A large portion of Northern and Eastern portions of studied areas which showed moderate to good protective capacity.