Physicochemical Evaluation of Groundwater Quality in the City of Léré and its Surroundings, Mayo Kebbi West Region, South- Western Chad

Abstract

Groundwater is the principal source of domestic water in the city of Léré and its surroundings, Mayo-Kebbi-West Province, south- western Chad, yet its quality had never been systematically assessed prior to this study. This work aimed to (i) characterize the physicochemical quality of groundwater from fifteen sampling points, comprising seven boreholes (F1-F7) and eight wells (P1-P8), and (ii) evaluate its suitability for domestic use against World Health Organization guideline values (WHO, 2022). In-situ parameters (temperature, pH, electrical conductivity, total dissolved solids, and turbidity) were measured with a multiparameter probe (WTW 2000); major cations and anions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃⁻, SO₄²⁻, NO₃⁻, Cl⁻) and total iron were analysed, following standard methods. Temperature ranged 28.8-33.0 °C, electrical conductivity 387-5040 µS.cm⁻¹, total dissolved solids 193.5-2521.7 mg.L⁻¹, and turbidity 0.08-66.5 NTU, with the highest mineralisation recorded at borehole F1 and the lowest at well P3. Calcium, magnesium, nitrate, bicarbonate, chloride and total hardness exceeded WHO values at one or more sites, whereas pH, sodium, potassium and sulphate remained within limits throughout; iron exceeded the WHO threshold (0.3 mg.L⁻¹) in three boreholes. A weighted-arithmetic water quality index (WQI) classified all eight wells and one borehole as excellent, one borehole as good, two boreholes as poor, and three boreholes (F1, F6, F7) as unfit for direct consumption owing chiefly to excess iron and mineralisation. Overall, groundwater quality around Léré was spatially variable; treatment is required for boreholes classified as poor or unfit for direct consumption. Regular hydrochemical monitoring and household-level treatment are recommended.