Assessment of Radioactivity Levels and Associated Radiological Hazards Index in Lake Water from Eastern Areas of Lake Hawassa, Sidama Region, Ethiopia

In this study, naturally occurring radionuclide concentrations and their respective radiological hazard indices in water samples collected from the eastern area of Lake Hawassa were measured. Analysis was conducted using HPGe gamma-ray spectrometry for the radionuclides 238U (214Pb and 214Bi), 232Th (228Ac), and 40K. Activity concentrations were found to range between below the detection limit (BDL) and 4.2 ± 0.8 Bq L⁻¹ for 238U, BDL and 9.1 ± 1.1 Bq L⁻¹ for 232Th, and BDL and 92.1 ± 4.5 Bq L⁻¹ for 40K with averages of 2.4 ± 0.6, 6.1 ± 0.6, and 55.1 ± 2.8 Bq L-1, respectively. Radiological hazard indices were determined and found to be the external hazard index ( = 0.04), absorbed dose rate ( = 7.14 nGy h⁻¹), and annual outdoor effective dose equivalent ( = 0.009 mSv y⁻¹). These values were compared with international guidelines and other countries' data on natural radioactivity. From the comparison, it is evident that the detected radionuclide activity concentrations and their respective radiological hazard indices comply with internationally recommended limits, implying that the lake water poses no significant radiological risks to the local population. In addition, the gathered information is used as initial reference data but not as the final baseline value for Lake Hawassa regarding radiological hazards. These data will play an important role in establishing future environmental policies and programs for the study area.