Water quality of the Helvetian and Eocene aquifers in Al Zerba catchment and southern parts of Al Qweek Valley, Aleppo basin, Syria

Groundwater is a key factor for sustainable socio-economic development in arid and semi-arid countries. The study area constitutes the south and southwestern parts of Aleppo basin, north of Syria. It is characterized by semi-arid climate and limited water resources. The aims of this study are to evaluate the groundwater quality with concern to drinking and irrigation suitability, water–rock interaction, and potential source rock to assess the main hydrochemical processes controlling chemical composition of groundwater in the Neogene and Paleogene aquifer systems. Hydrochemical data of 29 irrigation and observation wells distributed in the region were used in this study. Concentrations of the dominant ions are following the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃ ⁻ > Cl⁻ > SO₄ ²⁻ for major cations and anions, respectively. Ca–Na–HCO₃, Na–Ca–SO₄, and Ca–Na–Cl are the main groundwater types in the region. The graphical interpretation and cluster analysis of groundwater samples identified three main hydrochemical facies in the region. These groups are differentiated by three levels of total dissolved solids (TDS) value ranges from 390 mg/l for the group A, 742 and 1795 mg/l for the group B and C, respectively. The results also show that most of the groundwater samples are close to saturation or oversaturation with respect to the minerals: aragonite, calcite, and dolomite, while halite and gypsum are always under-saturated. Furthermore, the inverse geochemical modeling of groundwater samples indicates three main processes that are responsible for groundwater evolution in the region: plagioclase weathering (albite, hypersthene), de-dolomitization, and cation exchange. These processes increase in groundwater salinity from the east to the southwestern parts of the study area. The groundwater in the region is partly critical for drinking and irrigation due to the high average TDS (925 mg/l), nitrate (43.78 mg/l), and salinity. However, groundwater samples exhibited low sodium adsorption ratios, moderate magnesium hazard, and low residual sodium carbonate. Despite of that, this type of water can adversely affect the soil and crops yields in the long term and prevent a sustainable development of agriculture in the region of interest.