Journal of Geoscience and Environment Protection, 2022, 10, 45-64 https://www.scirp.org/journal/gep ISSN Online: 2327-4344 ISSN Print: 2327-4336 DOI: 10.4236/gep.2022.1012004 Dec. 8, 2022 45 Journal of Geoscience and Environment Protection Groundwater Geochemistry and Saltwater Intrusion in the Dakar Coastal Area, Senegal Ousmane Coly Diouf 1* , Lutz Weihermüller 2 , Mathias Diedhiou 1 , Edgar Y. Terence Benam Beltoungou 1 , Ndeye Maguette Dieng 1 , Seynabou Cissé Faye 1 , Harry Vereecken 2 , Serigne Faye 1 1 Geology Department, Faculty of Sciences and Techniques, Cheikh Anta Diop University of Dakar, Dakar, Senegal 2 Forschungszentrum Jülich GmbH, Agrosphere Institute IBG-3, Jülich, Germany Abstract Groundwater levels and water samples were collected from 20 drinking water pumping and piezometer wells in the urban area of Dakar coastal region in the year 2019. The pH-value, electrical conductivity, as well as calcium, mag- nesium, sodium, potassium, chloride, sulfate, bicarbonate, and nitrate con- centrations were measured to assess the hydrochemical quality of the infra- basaltic aquifer in the area. The present work carried out a hydrochemical analysis to interpret the groundwater chemistry of the aquifer. The results of this chemical analysis indicate that Na + > Mg 2+ > Ca 2+ > K + was the most do- minant cation sequence in the groundwater, while Cl − > 3 HCO − > 2 4 SO − > 3 NO − was the most dominant one for anions. The chemical analysis of our samples showed, that the Cl-Ca-Mg facies was dominant in the aquifer, while Cl-Na-K and HCO 3 -Na-K facies represent 20% and 10% of the groundwater sampled, respectively. A comparison of the measured groundwater quality in relation to WHO drinking water quality standards revealed that 80% of the water samples are suitable for drinking purposes. Ca enrichment, Simpson ra- tio, ratio of sodium chloride, and calculating Base Exchange (BEX) indices for the samples revealed that the groundwater is mainly affected by three factors: seawater intrusion due to aquifer overexploitation on one hand, and freshen- ing processes and nitrate pollution, on the other, mainly caused by the ground- water flow from the unconfined aquifer. Keywords Coastal Groundwater, Major Ions, Hydrochemical Facies, Anthropogenic Activities, Nitrate Pollution How to cite this paper: Diouf, O. C., Weihermüller, L., Diedhiou, M., Beltoun- gou, E. Y. T. B., Dieng, N. M., Faye, S. C., Vereecken, H., & Faye, S. (2022). Ground- water Geochemistry and Saltwater Intrusion in the Dakar Coastal Area, Senegal. Journal of Geoscience and Environment Protection, 10, 45-64. https://doi.org/10.4236/gep.2022.1012004 Received: October 18, 2022 Accepted: December 5, 2022 Published: December 8, 2022 Copyright © 2022 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access