Geospatial applications in delineating groundwater prospect zones in a hard rock terrain: an integrated approach

Abstract

This study involved the application of geospatial techniques to delineate groundwater potential zones in a hard rock terrain of Oban Massif and environs. This goal was achieved using satellite remote sensing imagery and geographic information system techniques. The method mapped groundwater-controlling factors such as geology, geomorphology, lineament density, slope, land use and land cover and drainage density. The study covered a total area of 677,298 km2. Landsat ETM+ imagery, Shuttle Radar Transmission Mission (SRTM), topographic and geological maps and ASTER DEM were used in the analysis. Software used for image processing, digitizing and lineament density computation are ArcGIS10.1, ENVI 4.2 and PCI Geomatica, respectively. Supervised classification method was applied in land use and land cover mapping. Analysis of satellite imagery shows that band 4 was the best for showing textural features for lineament extraction. The method of multi-criteria evaluation by assigning relative weights to each groundwater-controlling factor was used to produce their corresponding thematic maps. The thematic maps were produced by weighted linear combination; each class individual weight was multiplied by the map scores and then adding the results. Overlay analysis of the thematic maps produced the groundwater potential map. Results show four groundwater prospect zones classified into very good (38,365 km2), moderately good (230,999 km2), fair (381,865 km2) and poor (26,068 km2). From this study, it is evident that lineament mapping is not the overriding factor in groundwater occurrence; other groundwater controlling factors are necessary for a more credible groundwater potential modeling. Lineament, slope, geology and geomorphology are the most influential groundwater controlling factors in the study. Comparison of the results of this study with the collected sample data shows reasonable accuracy. These findings are useful for borehole siting and environmental management strategies for groundwater potential investigation in both Nigeria and other parts of world.