Groundwater chemistry of weathered zone aquifers of an area underlain by basement complex rocks

Abstract The chemical constituents of groundwater commonly reflects the environment of occurrence including geological, biospherical and human inflences. The chemical constituents of groundwater in the shallow aquifers of the weathered basement complex would normally be expected to reflect the geology and the weathering conditions. Groundwater samples from 86 dug wells in Ilesha, a city located in the basement complex environment of Southwestern Nigeria have been analysed for dissolved ions. The data obtained from the analyses were subjected to pattern recognition techniques through multivariate cluster analyses. The results show that there is a human activity imprint on the groundwater chemistry which overshadows the normally expected influence of weathering and bedrock geology. The results of the study have implications for groundwater development schemes in urban areas, and peri-urban land use planning and future development in towns and cities on the basement complex, which constitute a significant portion of Africa.