In order to evaluate the radiological baseline in the Lake Van basin, U-238, Th-232,, Ra-226 Cs-137 and K-40 activity concentrations and gross radioactivity were determined in twelve river water and sediment samples. To determine radionuclide activities and gross radioactivity, a gamma ray spectrometer with HPGe detector and a gross-alpha/beta-counting system low background multi-detector were used, respectively. Therefore, based on the measured activity concentrations,. parameters of radiological hazards such as radium equivalent activity, outdoor absorbed dose rate, annual effective dose, and internal and external hazard indices were calculated. R-eq, H-ex and H-in and values in samples were generally lower than worldwide average values; while D-out, and AED values were higher than worldwide average values in general.