2D Resistivity Survey for Groundwater Exploration in a Hard Rock Terrain: A Case Study of MAGDAS Observatory, UNILORIN, Nigeria

摘要

A 2D electrical resistivity survey has been carried out for water exploration at the MAGDAS Observatory, University of Ilorin. This is in view of the possibility that the observatory could gain international recognition and therefore the need to secure the area from acute water shortages for observers and researchers. The area lies within the basement rock terrain of West Central Nigeria and bounded by longitudes 4° 39'-4° 42'E and latitudes 8° 28'-8° 30'N. The survey was carried out using PELI 1300 portable terrameter while a total of 18 VES with 20 m station interval were completed in 3 even parallel profiles by means of Schlumberger configuration. The results revealed the presence of three geo-electric layer in the study area. The top lateritic soil has resistivity values ranging from 200 to 500 Om and thickness of 3 to 7 m. The weathered basement has resistivity values from 10 to 500 Om with thickness of 10 to 30 m while the fresh basement layer has resistivities greater than 900 Om. The analysis of resistivity and thickness maps reveal that the Western parts of the study area have relative low resistivities in the fractured weathered rocks coupled with thickness more than 25 m. This is consistent with aquiferous layer and therefore, such area maybe recommended as targets for groundwater tube drilling.