<p>Understanding the distribution, circulation and hydrochemical evolution of groundwater in bedrock aquifers is critical for groundwater resource assessment and the safety evaluation of underground high-level radioactive waste (HLW) facilities. Groundwater chemistry can provide insights into the characteristics of flow systems, but may require extensive observational data. This study employed multiple methods to define the zonation of groundwater flow systems and hydrochemical evolution processes in the Beishan area, China, to support the identification of sites suitable for geological disposal of HLW. Results revealed that the main hydrochemical types of groundwater in bedrock aquifers were Na-Cl·SO₄ and Na-SO₄·Cl, with a clear correlation between hydrochemical composition and the distribution of flow pathways. Total dissolved solids (TDS) provided a valuable indicator for the zonation of different groundwater flow systems. Evaporation and water-rock interactions, particularly halite and gypsum dissolution, were the dominant processes influencing the hydrochemical composition of groundwaters, whereas water interaction with aluminosilicate minerals was minimal. Groundwater systems were categorized into local, intermediate and regional flow systems, with local systems accounting for over 90 % of the total flux. Hydrochemical types transitioned from Na-Cl·SO₄ in recharge areas to Na-Cl in discharge areas. In the recharge areas and throughflow regions, hydrochemistry was primarily controlled by leaching processes, whereas evaporation, mixing and mineral precipitation dominated in the discharge areas. This study enhances the understanding of complex flow systems and hydrogeochemical processes in bedrock aquifers, contributing critical insights for the long-term safety assessment of HLW disposal sites.</p>