Hydrogeology of the coastal region of Ondo State, Nigeria.

Yinusa Ayodele Asiwaju-Bello¹ and Joshua Oluwasanmi Owoseni²
Department of Applied Geology, Federal University of Technology Akure, Nigeria.
¹E-mail: ayoasiwajubello@futa.edu.ng
²E-mail: joowoseni@futa.edu.ng; jo.owoseni@gmail.com
²ORCID: http://orcid.org/0000-0001-9992-4569

Abstract

A study of the climatic and geologic conditions affecting groundwater resources in the coastal region of Ondo state, south-western Nigeria, has been done. Data obtained from existing boreholes and hand-dug wells were used to delineate underlying aquifer units, and to explain the chemical quality of the groundwater in the area. The Ondo State coastline is 80km long. Deep-seated water table condition occurs in most parts of the coastal region except Igbokoda area. This makes hand-dug wells difficult to construct in the region. Based on calculated transmissivity values, the Ise, Araromi and Benin formations, as well as the Recent Alluvium, constitute the main water-bearing units in the region. From borehole records, four aquifer horizons have been established. Aquifer-1, which supports shallow hand-dug wells in Igbokoda area, has been found to contain brackish water in some places which show evidence of pollution from seawater. The local groundwater flow direction here was inland from the coastline.

Keywords: Ondo State coastline, Sea-water pollution, Benin formation, Groundwater quality