HYDROGEOLOGICAL AND HYDROGEOCHEMICAL CHARACTERIZATION OF OWO AREA, SOUTHWESTERN NIGERIA USING REMOTE SENSING AND GIS

Abstract

The application of remote sensing and GIS in groundwater potential characterization has been internationally acclaimed. Owo and its environment lack sufficient groundwater data that can aid proper planning and management of the resource. For this reason, the groundwater potential carried out using remote sensing and GIS. After desk study, Landsat TM (Bands 1-7) of 1988 was acquired and processed using ENVI 4.3™, ERDAS 9.1™ and ILWIS 3.7™ softwares. The image enhancements used are the linear stretching, equalization and low pass Gaussian methods. For drainage mapping, Bands 5-4-3 were combined in a RGB (123) format. For lineament extraction, the Digital Terrain Model (DTM) was generated from the Shuttle study of Owo and its environment within the Basement Complex was Radar Topographic Mission (SRTM) data which were corrected for bad values. The DTM was used in manually extracting lineaments in the study area through on-screen digitization. The groundwater potential of the area was deduced using score values assigned to each parameter studied. Thematic maps were generated for slope, topography, land-use, rainfall, lithology, lineament density and lineament intersection; these were overlaid to generate the groundwater potential map. Results indicate that Isijogun, Iyere, Owo Township, Ehinogbe and Sanusi have the highest groundwater potential where productive wells can be drilled. Geochemically, groundwater in the study area is found to be excellently suitable for irrigation as the Sodium Adsorption Ratio values generally range between 1 and 10. Over eighty percent of the sampled water is soft water, making it suitable for drinking as it falls within the acceptable limits of the World Health Organization (WHO) standards.