Limited knowledge exists regarding the potential risks associated with anthropogenic release of rare earth elements (REEs) in the environment. This study aimed to investigate REE signatures in the watershed Poyang Lake, the largest freshwater lake in China. Samples of surface water, wastewater, and groundwater were collected from five rivers discharging into the lake. Results revealed wastewater from wastewater treatment plants contained total REE concentrations from 231 to 904 µg/L, exceeding those found in surface water (0.4 to 1.3 µg/L) and groundwater (0.5 to 416 µg/L). Samples with elevated REE were found in Ca-Mg-Cl/SO4 type waters and exhibited an 18 O-D deviation from local meteoric water line. Wastewater exhibited a higher positive Gd anomaly compared to surface water and groundwater, attributed to anthropogenic input of Gd (Gdanth). The determined Gdanth concentration ranged from 0.04 to 0.21 µg/L, and from 0.06 to 0.37 µg/L, accounting for 4% to 21% and 49% to 84% of total Gd concentrations in groundwater and surface water, respectively. Gdanth concentration in wastewater (0.19 to 0.43 µg/L) remained constant in effluent after wastewater treatment. Surface water displayed relatively complex normalized REE patterns influenced by anthropogenic activities and natural processes (weathering and complexation), while groundwater exhibited heavy REEs enrichment, due to carbonate solution complexation. Additionally, Gdanth concentration showed a positive correlation with ΣREE, Pb, Ni, and Co concentrations in groundwater, indicating a good pollution tracing potential. Health risk assessment using the hazard quotient (HQ) suggested higher HQGd values in groundwater compared to surface water. Residents in the eastern part of Poyang Lake were found to face higher risks associated with Gd in groundwater compared to the western part, with infants and children at greater risk than adult males and females. These findings offer valuable insights into environmental behavior and health risks of REEs in aquatic systems impacted by human activities.