Application of SRTM DEM and Electrical Resistivity Techniques to Delineate Favourable Borehole Sites for Groundwater in Parts of Minna Sheet 164 SW, North-Central Nigeria

Abstract

A combination of Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) and electrical resistivity were applied in parts of Minna, Sheet 164 SW, North-Central Nigeria to delineate favourable sites for drilling boreholes. Lineaments were extracted from derivative map of SRTM DEM datasets. Selected thematic layers which included lineaments, geologic structure and parametric maps derived from Vertical Electrical Sounding (VES) data were integrated and modelled using ArcGIS to generate a groundwater potential map of the area. Seventy VES were conducted using the Schlumberger array with a maximum AB/2 distance of 100 m and 500 m spacing between each VES sounding stations, to study the variation of resistivity of the ground at variable depths. Geologic mapping results revealed granite as the major lithology with schist occurring in the east. Principal joint directions and automated lineaments map of the combined four relief images trend in the NE - SW direction indicating weathering and probable high groundwater potentials along this direction. VES results revealed up to six geoelectric layers with different resistivities and depths. Six different geoelectric curves were generated from the analysis namely: HA, AA, HK, AK, KH and QH portraying various aquifers within the region. VES results also revealed that the area has undergone slight weathering (less than 6 metres in most parts) and is fractured from place to place. The fractures were found to be convergent to the middle portion of the study area indicating more groundwater accumulation towards that direction. Drill depths in this area should target a minimum of 100 m to ensure sufficient and sustainable supplies to drilled wells.