<p>The study investigated groundwater quality, irrigation suitability, health risks, and hydrochemical control mechanisms in the Hailar Basin. The water quality index (WQI) was used to evaluate drinking-water suitability, while the U.S. Salinity Laboratory (USSL) diagram, Wilcox diagram, and permeability index (PI) were applied to assess irrigation suitability. Hydrogeochemical and statistical methods were used to identify the main processes controlling groundwater evolution. The results show that groundwater is mainly of the HCO₃–Na·Na type in the Herhongde Sag, Cl–Na and HCO₃–Na types in the Cuogang Uplift, Wuerxun Sag, and Beier Sag, HCO₃–Na type in the Bayanshan Uplift, and Cl–Na type in the Hongqimuchang Sag and Xinbaolige Sag. In the study area, 13% of samples exceeded the limit for NO₃⁻, 72% for As, 90% for F⁻, and 71% for U. Health risk assessment indicated potential non-carcinogenic risks from As, U, and F⁻ ingestion, with mean hazard index (HI) values of 18.10 for adults and 50.66 for children, and unacceptable As related carcinogenic risks. According to the WQI results, 36.84% of groundwater samples were classified as excellent or good for drinking, whereas 15.79% were very poor. The irrigation assessment indicates that groundwater presents low to moderate sodium hazard levels but moderate to extremely high salinity hazard levels, with most samples falling within the C2S1, C3S2, and C4S2. The groundwater chemistry is mainly controlled by rock weathering and evaporative crystallization, and is further influenced by arid to semi-arid climatic conditions and intensified anthropogenic activities.</p> Graphical abstract