Hydrogeophysical Investigation of Groundwater Systems in Otukpo, Benue State, North-Central Nigeria

Abstract

Hydrogeophysical investigations employing electrical method was adopted for groundwater exploration in Otukpo. Data collected from geophysical investigations and from one borehole were used in this research. Six (6) Vertical Electrical Soundings (VES) were carried out in the study area using the Schlumberger configuration of electrical resistivity method with a maximum AB/2 of 600 m. Qualitative and quantitative interpretations of the data were carried out employing the traditional curve matching and the digital computer iteration methods. The VES readings from shallow subsurface to the depth of about 500m of the VES stations ranges from 3 Ωm to 1250 Ωm, interpreted in the area as loess sand, silty-sand clay, shale and sandstone from top to bottom based on the resistivity data. The deeper groundwater system in the area is confined at an approximate depth of 500 m. a shallow unconfined aquifer (aquitard) and a deeper confined aquifer are the two principal types of aquifer existing in the study area. Future borehole in the area that would tap water from the confined aquifer likely to be terminated at a depth of about 450 m to 500 m. based on the detailed geophysical investigations which confirmed the sandstone formation.