This study investigates the hydrochemical formation mechanism of shallow groundwater in the Upper Kebir upstream sub-basin (Northeastern Algeria). The objective is to evaluate water quality suitability for domestic purposes through the application of water quality index (WQI). A total of 24 water points (wells and borewells) evenly distributed in the basin were collected and analyzed in the laboratory for determining the major ions and other geochemical parameters in the groundwater. The groundwater hydrochemical types were identified as Cl–Na and Cl–HCO₃ –Na, with the dominant major ions were found in the order of Na⁺ > Ca²⁺ > Mg²⁺ for cations, and Cl⁻ > SO₄²⁻ > HCO₃^– > NO₃⁻ for anions. Results suggest that weathering, dissolution of carbonate, sulfate, salt rocks, and anthropogenic activities were the major contributors to ion content in the groundwater. The Water Quality Index (WQI) was calculated to assess the water quality of potable water. Approximately 50% of the sampled sites exhibited good water quality. However, the study highlights significant NO₃ contamination in the study area, with 50% of samples exceeding permissible limits. Therefore, effective treatment measures are crucial for the safe consumption of groundwater.