Citizens are advised to store enough food to last those 10 days, because initially a disaster might put national emergency services beyond reach. Five days’ water – two liters (half a gallon) per person daily – is advised. The document said “an attack on German territory, requiring conventional defense of the nation, is unlikely”. But, it said, a major security threat to the nation in future could not be ruled out, so civil defense measures were necessary.

Germans told to ‘stockpile food and water’ in civil defence plan – Telegraph.co.uk