GEOPHYSICAL SURVEY FOR GROUNDWATER DEVELOPMENT IN GBAMZE AND ENVIRONS, PARTS OF AKWANGA SHEET 209 SW, NORTH CENTRAL NIGERIA

Vertical Electrical Sounding (VES) method was used in carrying out geophysical investigation for groundwater in Gbamze and environs with a view of determining the apparent resistivity and thickness of various layers of the geological formations, the depth to the bedrock, and references of lithologic units. Vertical Electrical Sounding (VES) using Schlumberger array was done at twenty four (24) VES stations using GPS Garmin XP to establish sounding points. The L and R tetrameter was used for the data acquisition. The field data obtained were analysed using computer software Iplwin and Ixld inversion. Results got from the interpretation suggest six layers in virtually all parts of the study area. The topsoil layer resistivity varies from 25.04Qm to 413.50f2m having thickness that ranges from 0.24m to 8.71m. The second layer contains clay, laterite and sand. Its thickness and resistivity values are 0.76m to 4.08m and 27.55Qm-7547.6Qm respectively. The third layer also consists of sandy clay, laterite and clayey sand. Its thickness ranges from 2.07m to 10.29m and the resistivity varies from 19.27Gm tol2.65.60Gm. The fourth layer has thickness and resistivity values of 2.85m to 18.80m and 22.35Qm to 605.30£2m respectively. This is mainly of highly fractured/weathered basement rock units. The fifth layer is a partially weathered/fractured basement rock unit. Its thickness and resistivity ranges from 3.82m to 15.99m and 64.26Qm to 1224Qm respectively. The last layer, being fresh basement rock unit has resistivity values ranging from 221.80Gm to 19863.40f2m. The general depth to basement and the groundwater potential varies from location to location but can be inferred as very good, moderate and poor areas.