The Arieș River is a middle-sized water stream, located in the NW of Romania, near to a mining area (in the middle basin) and an industrial facility (in the lower basin). Due to its geographic location and its significance in the Mureş–Tisza Basin, the Arieș River has a major impact on its emissary quality. Therefore, the dynamics of hydrochemical major parameters of surface waters sampled from a selected sector of Arieș River were analyzed. A total of12 different water quality parameters (HCO₃^-, Cl^-, F^-, NO₂^-, NO₃^-, SO₄^2-, PO₄^3-, Ca, Mg, Na, K, Fe) from 10 surface water sampling points situated in different locations along the water stream, collected in 4 different seasons in 2020, were analyzed in a laboratory. The findings indicated that the water samples were more contaminated in the mining area, compared to the samples near the industrial facility. The highest Na (19.2 mg/L), Mg (13.7 mg/L), K (14.7 mg/L), and Ca (314 mg/L) concentrations were obtained near a copper mining facility. The Piper and Durov diagrams classified the waters into the Mg-HCO₃^- and Ca-Cl^- types. It was noticed that there is no clear temporal variability in the major water quality parameters, indicating that natural processes have no major impact on the water quality. Past and present mining and industrial activities have an impact on the water chemistry, altering the quality of the Arieș River. Thus, pollution prevention and curation treatments are required before water use.