Abstract

Geoelectric study involving fifty four (54) Vertical Electrical Soundings (VES) has been undertaken within Ijare, southwestern Nigeria with the aim of evolving the hydrogeologic setting of the town. Ijare is underlain by the Precambrian Crystalline Basement Complex rocks with inhabited parts of the town underlain by migmatite gneiss and fine-grained biotite granite while inselbergs of older granites suites adjoins the town on all sides. Based on the hydro-geoelectric characteristics obtained from geoelectric sections and maps, the study area is classified into low, moderate and high groundwater potential zones. Four geoelectric subsurface layers delineated from the study are the topsoil, weathered basement, fractured basement and the presumably fresh bedrock. The concealed ‘basement complex’ morphology is rugged in the town with concealed ridges underlying the central areas while the eastern and northwestern areas are underlain by irregular concealed depressions. The zones of concealed basement depressions with resultant significant overburden thickness constitute target areas for groundwater development in the town. Arising from the general classifications undertaken using the results of the geoelectric soundings, sustainable groundwater development schemes for Ijare is considered feasible on the eastern and northwestern flanks where groundwater potential rating varies from moderate to high.

Key words: Geoelectric, groundwater, basement, ridge, depression, overburden, fracture.