Hydrochemistry and Characterization of Shallow Groundwater of Vogan-Attitogon Plateau Southeastern Part of Coastal Sedimentary Basin (Togo)

Gbati Napo, Kossitse Venyo Akpataku, Tomkouani Kodom, Masamaéya D.T. Gnazou, Limam Moctar Bawa and Gbandi Djaneye-Boundjou

Background and Objective: The shallow Continental Terminal aquifer is the primary water resource for drinking purposes in the coastal sedimentary basin of Togo. This study aimed to identify hydrochemical processes and groundwater quality to ensure the sustainable water supply in the basin. Materials and Methods: Major chemical parameters of forty-two samples of shallow groundwater and eight samples of surface water collected during march 2019 were analyzed using AFNOR methods. The Piper diagram and Principal Components Analysis of the data were used to determining the factors that control groundwater processes in the aquifer system, based on the ionic constituents, water types and component loadings. Results: Groundwater was slightly acid and fresh to brackish. Surface water was circum-neutral and fresh to very saline. For both groundwater and surface water, the cations and anions abundance order was Na⁺>Ca²⁺>Mg²⁺>K⁺ and Cl^–>SO₄^2–>HCO₃^–>NO₃^–, respectively. Thus, water samples were predominantly Na-Cl water type (~88%). Most of the groundwater samples were classified Na-Cl water type with two accessory water types (Ca-Cl and Ca-Mg-Cl). The principal process operating in the shallow groundwater of the Vogan-Attitogon plateau was seawater mixing with fresh water and natural silicate weathering. Carbonaceous debris, limestone weathering, pyrite dissolution, ion exchange, evaporation, anthropogenic activities (farming using fertilizers and industrial activity) also influenced groundwater mineralization. Conclusion: The analysis of shallow groundwater shows for some samples high Total Dissolved Solids and ions found in concentrations exceeding thresholds. The shallow aquifer of the Vogan-Attitogon plateau face degradation of water quality and the consumption of this water may affect human health.

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