Drinking water production facilities using groundwater are hardly sensitive for a nation-wide radiological contamination. Travel times for a radiological contamination in dune sand, river bank filtrate or deep groundwater are long leading to significant radioactive decay, especially for the short-lived nuclides. Furthermore, sand, sludge and clay have specific adsorption characteristics resulting in a much slower transport of a decontamination than the transport of groundwater itself. Basically, during a radiological contamination direct problems in drinking water production out of groundwater are not expected. It is much more likely that contaminated surface waters as a source for drinking water will present a problem.
The possible counter measures to adjust the drinking water purification process are limited. The most important short notice options are removal of contaminated waters to the sea and, during the passage of a fall-out cloud, minimize aeration in the purification process. In serious situations a contaminated intake point is (temporarily) closed until all radionuclides have decayed.