Possible radioactive contamination of Wiese water and raw water of drinking water supply by a severe nuclear accident

For the drinking water supply from Basel, Rheinwasser is seeped away and treated in a drinking water treatment plant after a passage through soil and groundwater strata. The drinking water supplier from Basel, IWB, intends to use as an alternative raw water source the river Wiese, if the water of the Rhine would not be suitable for use due to contamination. The OEko-Institute was commissioned to investigate the extent to which the water of the Wiese could be contaminated with radionuclides during a serious accident in a Swiss nuclear power plant. Releases of radioactive substances were assumed based on the accident in Fukushima-Daiichi and the possible entry into the Wiese was estimated with different fallout and washout scenarios. For this purpose, a compartment model was constructed and, among other things, earlier work on transport and exchange processes between river and ground water along the Wiese was used. In addition, a validation was carried out using the observations of the activity concentrations in German rivers after the reactor disaster in Chernobyl. The contamination of the Wiese water would fall below the Swiss tolerance values for the radionuclides considered in between 14 days. Since the Wiese water for the generation of drinking water does not have to be continuously seeped, but an interruption of 14 days does not affect the production of drinking water, the investigation showed that the Wiese is a suitable option for the supply of raw water.