Evaluation of Groundwater Prospect in a Clay Dominated Environment of Central Kwara State, Southwestern Nigeria

Abstract

In this research, groundwater prospect of Central Kwara have been investigated using electrical resistivity method for both domestic and industrial application in the face of scarce water resources, occasioned by incessant borehole failure/low yield, has prompted researches for viable source of water. The central Kwara state falls within the basement complex region of Nigeria known as the hard rock terrain, where availability of groundwater is dependent mainly on structural features. The general curve types obtained from the study area were H, HA, KH and HKH types with the H curve type more prominent in the study area. Three geoelectric sections generated with resistivity parameters ranging between 350 to 1900 ohm-meters, 7.7 to 99.1 ohm-meter and above 3000 ohm-meter; making up the topsoil, weathered layer and bedrock respectively. The topsoil is interpreted as laterite/hard pan within thickness range of 0.4 and 2.2 m while the weathered layer zone ranged between 0.9 to 36.1 m thickness respectively; making the overburden of the area with thickness range of 1.4 to 42.7 m. The bedrock resistivity ranges from 400 ohm-meter to 8192 ohm-meter, indicative of weathered/fractured and fresh basement respectively. The results of the vertical electrical sounding were used to generate clay horizon resistivity map, clay horizon thickness map, aquifer resistivity map and overburden thickness map. This study reveals that the study area is dominated by clay which lead to borehole failure and dry up of hand pump well because most of the hand pump well were terminated within the clayey formation.