Author(s)

Djim M. L. Diongue^1*, Laila Sagnane¹, Huguette Emvoutou², Maria Faye¹, Ibra D. Gueye¹, Serigne Faye¹

¹Geology Department, Cheikh Anta Diop University, Dakar, Senegal.
²Department of Earth Science, University of Douala, Douala, Cameroon.

A regional groundwater quality evaluation was conducted in the deep Maastrichtian aquifer of Senegal through multivariate statistical analysis and a GIS-based water quality index using physicochemical data from 232 boreholes distributed over the whole country. The aim was to 1) identify the water types and likely factors influencing the hydrochemistry, and 2) determine the suitability of groundwater for drinking and irrigation. Results showed that sodium, chloride, and fluoride are highly correlated with electrical conductivity (EC) reflecting the significant contribution of these elements to groundwater mineralization. The principal component analysis evidenced: 1) salinization processes (loaded by Na⁺, K⁺, EC, Cl^-, F^- and HCO₃^-) controlled by water/rock interaction, seawater intrusion and cation exchange reactions; 2) dolomite dissolution loaded by the couple Ca²⁺ and Mg²⁺ and 3) localized mixing with upper aquifers and gypsum dissolution respectively loaded by NO₃^- and SO₄^2-. The hierarchical clustering analysis distinguished four clusters: 1) freshwater (EC = 594 μs/cm) with mixed-HCO₃ water type and ionic contents below WHO standard; 2) brackish (Na-mixed) water type with moderate mineralization content (1310 μs/cm), 3) brackish (Na-Cl) water type depicted by high EC values (3292 μs/cm) and ionic contents above WHO and 4) saline water with Na-Cl water type and very high mineralization contents (5953 μs/cm). The mapping of the groundwater quality index indicated suitable zones for drinking accounting for 54% of the entire area. The occurrence of a central brackish band and its vicinity, which were characterized by high mineralization, yielded unsuitable groundwater for drinking and agricultural uses. The approach used in this study was valuable for assessing groundwater quality for drinking and irrigation, and it can be used for regional studies in other locations, particularly in shallow and vulnerable aquifers.

Groundwater Quality Index, Maastrichtian, Statistical Analysis, GIS

Diongue, D. , Sagnane, L. , Emvoutou, H. , Faye, M. , Gueye, I. and Faye, S. (2022) Evaluation of Groundwater Quality in the Deep Maastrichtian Aquifer of Senegal Using Multivariate Statistics and Water Quality Index-Based GIS. Journal of Environmental Protection, 13, 819-841. doi: 10.4236/jep.2022.1311052.