<p>This study addresses groundwater flow processes and hydrochemical evolution in the stratified hard rock terrain of the Seyabo and Feresmay River catchments, in Tigray, North Ethiopia. Geological, hydrogeological, hydrogeochemical, and isotopic methods were employed in this study. Hierarchical Cluster Analysis (HCA) classified the groundwater samples into two major groups and four subgroups based on ten parameters (EC, TDS, pH, Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl⁻, HCO₃⁻, and SO₄²⁻). The two HCA groups contained TDS &gt; 1000&#xa0;mg/l and TDS &lt; 1000&#xa0;mg/l, shows different water-rock interactions and depths of circulation. The isotopic composition of the groundwater samples ranged from − 1.7‰ to + 7.2‰ for δ²H, and − 1.55‰ to + 0.18‰ for δ¹⁸O, indicating recharge from evaporated local precipitation. The high pH observed in the Na–Ca–HCO₃ water type with elevated EC reflects deep groundwater circulation within confined aquifers. Recharge from locally evaporated precipitation is progressively modified along the north–south flow path, with salinity increasing from Ca–Mg–HCO₃–SO₄ facies in the recharge zone to Ca–Na–SO₄–HCO₃ midstream and Na–Ca–HCO₃ downstream. This geochemical evolution, confirmed by inverse geochemical modeling, is driven by silicate weathering, cation exchange (Ca²⁺–Na⁺), and CO₂ dissolution–degassing, coupled with evaporation.</p>