Abstract
Sustainable groundwater supplies in the terrain underlying by crystalline basement rocks require lineament analyses for proper sitting of boreholes. This study was carried out to illustrate the application and importance of Remote Sensing and Geographic Information System (GIS) techniques for efficient groundwater resource exploration and management. The study demonstrates the use of LANDSAT 7 ETM+ imagery, ASTER digital elevations models (DEMs) and geological maps for mapping and analyses of lineaments in the Basement Complex region of Ondo State, Nigeria. Digital image processing techniques involving linear / edge enhancements and directional filtering were applied on the image to enhance the edges of the linear features using ENVI 4.7. The enhanced image, normalized difference vegetation index (NDVI) image and hill shaded relief image (processed ASTER DEM) were visually interpreted through GIS overlay operations for lineaments extraction through on-screen digitizing using ArcGIS 9.3. The extracted lineaments were statistically analyzed to determine their lengths, densities and intersections. The results obtained were used to generate lineament density, lineament intersection map and rose diagram. The lineament / fracture analyses indicated that the area has numerous long and short fractures whose structural trends are mainly in the north-south and east-west directions. The cross-cutting lineaments are relatively high in areas around the central, north-eastern and south-western parts of the study area, and relatively low in the other areas. The zones of high lineament intersection density are feasible zones for groundwater prospecting in the study area. The study has led to the delineation of areas where groundwater occurrences is most promising for sustainable supply and hence, further geophysical survey can be concentrated.
Key words: Groundwater pattern mapping, lineament trend distribution, Landsat 7 ETM, NDVI.
