Review of Time of the Wolf (2003)
Michael Haneke (writer-director).
Almost no water is potable for some reason, so civilization has collapsed. A father leads his family to a sanctuary, or so he believes.
Post-apocalypse drama, with strong emphasis on the drama as opposed to the science fiction aspects. Causes and high-level developments are largely ignored. Susan Sontag would have been miffed.
References here: The Road (2006).