Characterization of the main karst aquifers of the Tezbent Plateau, Tebessa Region, Northeast of Algeria, based on hydrogeochemical and isotopic data

Chemical properties and hydrogeological characterization of water resources were studied in the Hammemt Plain, which is located in the northwest of the Tezbent mountain range, City of Tébessa, northeast of Algeria, which drains carbonate aquifers through various large karst springs. The physical and chemical characteristics of spring and well water samples were studied for 2 years in order to assess the origin of groundwater and determine the factors driving its geochemical composition. The ionic speciation and mineral dissolution/precipitation were calculated where we found that water wells, characterizing groundwater circulation at shallow depths, are moderate to highly mineralized waters of the Na-HCO₃ type. In contrast to the shallow environment, the CO₂-rich, deeper waters are of the Ca-HCO₃ type, and undergo significant changes in their baseline chemistry along flow lines with increasing residence time. The main factors controlling the groundwater composition and its seasonal variations are geology, because of the presence of different carbonate formations, additionally elevation, and the rate of karst development. Supersaturation with respect to calcite indicates CO₂ degasing occurs either inside the aquifer in open conduits or at the outlet in reservoirs. Undersaturation with respect to calcite shows the existence of fast flow and short residence-time conditions inside the aquifer. The main springs and wells of the Tazbent Mountain have been studied by means of stable isotope measurement, where the values are varied in ¹⁸O; between −8.2 and −7.76 for spring samples and from −8.26 to −7.15 for well samples and in ²H between −52.92 and −49.11 for spring samples and from −55.47 to −47.44 for well samples, showing that the groundwater recharge is of meteoric origin and suggests the absence of the evaporation effect on the isotopic composition.