REMOTE SENSING AND GIS APPROACH FOR ZONING GROUNDWATER POTENTIAL IN PARTS OF THE BASEMENT COMPLEX TERRAIN, SOUTHWESTERN NIGERIA

Abstract

An integrated approach using Remote sensing and Geographic Information Systems (GIS) was adopted to delineate groundwater potential zones in the study area in order to address the municipal, domestic and agriculture needs of the people. Satellite image was processed and interpreted to produce thematic maps such as lithology, lineaments, land cover, slope, soil and drainage. Drainage lines were digitized from the topographic map of the study area to produce a drainage density map. GIS analysis of distance for lineaments, density for drainage, slope for elevation and reclassification were done for each factor map. A groundwater model of the spatial data was developed using ArcGIS 10.2 model builder engine. The model was executed and groundwater potential map was generated. The groundwater potential zones were classified into five categories namely very low, low, moderate, high and very high. The potential zones were obtained by weighted overlay combination using the spatial analyst tool in ArcGIS 10.2 software. During the weighted overlay analysis, ranking was given for each parameter of the thematic maps and weights were assigned according to their influence such as lithology (35 %), lineament density (31%), slope (17 %), soil (9 %), drainage density (5 %), and land cover (3%). The spatial distributions of the various ground water potential zones obtained from the model generally correlated with regional patterns of lithology and lineaments. Spatially, the very high and high categories were distributed along areas close to lineaments, less dense drainage density and where the lithology is affected by secondary structure and having interconnected pore spaces. Subsequent validation with borehole yield data revealed a good correlation with respect to the observed groundwater potential zonation. The highest yielding boreholes lie in the high and very high ground water potential zones. The results demonstrated that the integration of remote sensing and GIS approach provided an effective tool in the assessment and management of water resources and development of groundwater exploration plans.