A blind geoelectrical survey commissioned to affirm or deny the presence of aquifer at a compound at Minna, Central Nigeria

Abstract

When the owner of a property, located on a knoll, tasked the survey crew to prospect for aquifer at his lot, no clue was provided as to what the result of an earlier survey by an independent crew was: thus, members of the present crew were required to independently plan and execute a geoelectrical survey at this same location, the result of which is expected to corroborate or weaken the conclusions reached in the earlier survey. At the outset, the client’s property was visually reconnoitered; the extent and preferred traverse directions were noted. The survey crew proposed a north-south (i.e. longitudinal traverse, LT) profiling scheme at 10m-separation between survey stations and 10m-separation between profile lines for the reconnaissance phase to a depth of 15m. Thence, detailed Vertical Electrical Sounding (VES) surveys were conducted for locations of “low-ohmic interest” to a depth of 100m. The result of the reconnaissance phase indicated the lowest resistance value of 1.6348Ω at “LT4-1.” Upon final VES surveys, and based on an empirical protocol for the likely presence of groundwater in the basement complex geological province, it was concluded that the prospect for aquifers of good yield at the area of study was very poor indeed: this conclusion actually corroborated the one drawn from the initial survey.