[en] Most of the old uranium mines in Portugal are located in the granite regions of the centre-north of Portugal (Beiras), in regions with relatively high population density. Most of the public water supplies for the villages and cities are from groundwater or from surface water reservoirs constructed on the rivers of the region. A survey of the radioactivity in the water supplies was carried out in order to investigate the concentration of radionuclides from the uranium family such as uranium, radium, polonium and lead radioisotopes. Radon was also determined, as well as total alpha and total beta radioactivity, in order to assess the human exposure through consumption of drinking water. In general the radioactivity content of waters is reasonably low, not too high for human consumption. In several cases, however, the concentrations of radionuclides such as dissolved radon, polonium and radium, or even uranium, are elevated with total alpha concentrations above 0.1 Bq/L. Cases of public water supplies with very high concentrations of dissolved radionuclides are rare and in general apply to spring waters that may come into contact with rocks containing localized mineralizations of uranium. The highest concentrations of radionuclides were measured in water from wells in areas under the influence of old mines, especially the ones where in situ leaching with sulphuric acid had been performed in the past. This is the case, for example, for Cunha Baixa and Quinta do Bispo, two old mines draining into the same valley. At present, most of these wells are used for irrigation purposes and drinking water comes from other supply sources. Consideration is given to the radiation doses to members of the public through water consumption from public supplies of these regions. (author)