Contribution of the Hydrogeological Study of Some Thermo-mineral Springs in the North-East of Algeria, Case study of Guelma, Souk Ahras, Tebessa, and Khenchela

Abstract

Thermo-mineral springs are widely distributed across northeastern Algeria and represent both a natural resource and a potential sector for therapeutic and tourism development. These waters exhibit significant variability in temperature, discharge, and chemical composition, reflecting heterogeneous hydrogeological conditions. This study aims to characterize the regional variability of hydrothermal systems in Guelma, Souk Ahras, Khenchela, and Tebessa, and to interpret groundwater circulation within the framework of hierarchical flow systems. For the first time in this region, the conceptual model of gravitational groundwater flow systems defined by József Tóth is applied to interpret hydrothermal circulation patterns. The methodological approach combines classical hydrogeological investigation with the gravitational flow system theory, incorporating hydrochemical analyses, isotopic measurements of δ¹⁸O and δ²H, characteristic ionic ratios, geothermometric estimations using Na/K, Na–Li, and Na–K–Ca geothermometers, and multivariate statistical analyses (principal component analysis and hierarchical cluster analysis). This integrated approach is used to identify the factors controlling water composition, the origin of recharge, and circulation pathways within hydrothermal units across a regional basin scale comprising hierarchical groundwater systems. Results show water temperatures ranging from 18 °C to 94.7 °C, and total mineralization varying from 424 mg/L in F6 (Khenchela) to 15,992 mg/L in S13 (Tebessa), reflecting contrasting circulation depths and degrees of water–rock interaction. Three dominant hydrochemical facies: calcium bicarbonate, calcium sulfate, and sodium chloride, which correspond to local, intermediate, and regional flow systems within the hierarchical groundwater circulation framework. Isotopic compositions confirm a meteoric origin for all thermal waters. Regionally, the Guelma province forms a distinct hydrothermal domain characterized by higher temperatures and specific mineralization patterns. Geochemical temperature estimations indicate that S7 (Guelma) and S13 (Tebessa) exhibit ion ratios and geothermometric signatures of chemically mature groundwater, suggesting prolonged circulation and stable hydrochemical evolution. This integrated framework enhances the understanding of hydrothermal processes and supports the sustainable development and management of geothermal resources in northeastern Algeria.Keywords: Thermal springs; Hydrochemistry; Stable isotope; Gravitational flow systems; Regionalhydrogeology; Principal component analysis (PCA)