TITLE:
Assessment of Hydrogeochemical Processes Affecting Groundwater Quality in the Eocene Aquifer of Diourbel, Senegal
AUTHORS:
Mouhamet Moustapha Diaw, Mathias Diédhiou, Ousmane Coly Diouf, Moctar Diaw, Serigne Faye
KEYWORDS:
Hydrogeochemical Processes, Groundwater Quality, Diourbel, Senegal
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.4,
April
22,
2026
ABSTRACT: Groundwater quality is an important factor in determining the health of the population and the development of various human activities. However, its hydrogeochemical characteristics and water quality in the Eocene aquifer remain poorly documented in the Diourbel region, in a context where the superficial layer is not very productive and the deep layer, brackish. To identify the presence of various hydrogeochemical processes and the factors determining groundwater quality, an investigation was conducted in the Eocene aquifer, using statistical methods, binary diagrams, the chloride-alkali index, and the saturation index. The results show that the pH of the groundwater was neutral to slightly alkaline (ranging from 6.7 to 8.3) and high salinity in some areas due to the presence of trapped seawater (TDS ranged from 276 to 2964 mg/L). The Piper Diagram shows three majors water types:
Ca-HC
O
3
−
(73%), Mixed-
HC
O
3
−
(13%) and Na-Cl (5%). The concentrations of alkaline earth minerals (Ca2+ + Mg2+) exceed those of alkalines (Na+ + K+) and bicarbonate (
HC
O
3
−
) dominates the majority of groundwater samples. Statistical approach shows an affinity between alkaline and alkaline-earth elements, suggesting a common origin, and a lesser affinity between nitrate (
NO
3
−
) and chloride (Cl−), indicating a marine origin of Cl−. Geochemical diagrams reveal that carbonate mineral dissolution/precipitation and reverse ion exchange processes are the most important factors governing groundwater chemistry, confirmed by the binary diagrams and the chloro-alkaline index. This study guarantees a solid basis for the knowledge of geochemical processes at the origin of water mineralization. It represents a starting point for good resource management measures.