TITLE:
The Salt Wedge Influence Demonstration on Groundwater in a Coastal Sedimentary Environment with a Marl-Limestone Predominance in the Commune of Akanda, Libreville North, Gabon
AUTHORS:
Igore Sylvano Boussougou Mouketou, Mike Castane Makaya M’Voubou, Lauriss-Paule Ngombi Pemba, Anli Bourhane
KEYWORDS:
Central Africa, Groundwater, Piezometry, Salinity, Season
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.8,
August
31,
2026
ABSTRACT: This study focuses on demonstrating the saltwater intrusion impact on the groundwater the Akanda area, located in the coastal area north of Libreville, by Gabon. Three boreholes (Iwosso, Parlementaires, and Makouengué) in this municipality were studied by measuring the electrical conductivity of the water and the static groundwater levels using specific probes. Since July 2024, these measurements have been taken monthly for conductivity, while piezometric measurements have been taken continuously. The results of this integrated study revealed an increase in the water level in all three boreholes as soon as the rains arrived, reaching the surface in the Iwosso borehole, rising from −10 m/soil in August to −0.74 m/soil in November 2024. Electrical conductivity values were very high (1180 µS/cm) only in the Iwosso borehole during the dry season. This could be explained by the dynamic freshwater-saltwater interface, manifested by seawater intrusion into the Iwosso aquifer. These electrical conductivity values gradually decrease as rainfall becomes abundant (rainy season) and freshwater recharge progresses. This phenomenon of rising piezometric levels accompanied by a decrease in electrical conductivity during the rainy season was also observed in the other two boreholes. The proximity of the Iwosso borehole to the sea is likely not the only factor contributing to this salinity, given that the two other boreholes are also located near the sea. Further investigations will be conducted soon to fully understand the occurrence of the saline wedge at Iwosso.