Characterization of the Bir-Hâmiya Hydrothermal Spring, Ouaddaï Region, Chad

Bir-Hâmiya thermal spring, located in Ouaddaï Province, eastern Chad, is a hydromineral resource that local communities have used for therapeutic purposes for generations, although it remains poorly documented in the scientific literature. This study characterizes its physicochemical properties and assesses their relevance for thermalism. Four sampling campaigns were conducted between January 2025 and May 2026. The parameters analysed were temperature, pH, electrical conductivity, total dissolved solids, total hardness, major ions (Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, SO42−), and NO3−, NO2−, F−, Mn2+, Fe2+, and NH4+. Data were interpreted using descriptive statistics, Piper, Stiff, Schoeller, and Gibbs diagrams, ionic ratios, and a correlation matrix. The results indicate a hot (48.6 °C), moderately mineralized thermal water with near-neutral pH and a calcium–magnesium–bicarbonate (Ca–Mg–HCO3) facies. Hydrochemical evolution is controlled by water–rock interaction and weathering of minerals of the Ouaddaï crystalline basement. Mean fluoride (2.15 mg/L) and manganese (0.23 mg/L) concentrations exceed WHO guideline values. These characteristics give the spring potential for thermalism and crenotherapy: the high temperature and the Ca–Mg–HCO3 facies may contribute to its therapeutic value, notably in rheumatological and dermatological conditions.