Investigation of Seawater Intrusion into Coastal Groundwater Aquifers of Escravos, Western Niger Delta, Nigeria

Abstract

In coastal regimes groundwater aquifers are often vulnerable to saltwater intrusion. Saltwater intrusion is often precipitated by natural hydrodynamic processes and overpumping of groundwater resource. Saltwater intrusion is presumed to have significant effect on quality of groundwater and accountable for lack of access to freshwater in the areas under study. The objective of this study is to use resistivity data obtained from vertical electrical sounding to ascertain the salinity of shallow aquifers, determine depth and thickness of freshwater aquifers. The Schlumberger array configuration was employed in acquisition of data. The maximum and minimum spacing between electrodes (AB/2) ranged from 2m to 250m. Resistivity values ranged from 0.24Ωm to 427Ωm, Values which ranged from 0.2Ωm to 4Ωm was construed to be aquifer saturated with saltwater, brackish water was inferred from resistivity values which vary between 7Ωm and 11Ωm, and clay was assigned to resistivity values that ranged from 17Ωm to 29Ωm. Effect of tide contributes to salinity of shallow aquifer around the seashore area. Aquifers saturated with saltwater are found at the depths of 10.5m, brackish water at 4m to 9m, while freshwater can be located from the depth of 19-46m. The study is able to reveal that groundwater quality has been compromised by intrusion of saltwater. We conclude that there is potential of saltwater intrusion into the freshwater lenses, which may be enhanced in the future by over- development of groundwater. 

Key words: Escravos, Vertical electrical sounding, Saltwater Intrusion, freshwater lenses, Aquifer, groundwater