Don't forget your hotwater heater as a source of water for local emergency use. that will get you 30-50+ gallons without doing a thing.
I keep 20L (in military water cans) for each member of the family, plus 0-2 cases of cheapo Costco bottled water that we use off and on as a family. how much we have in the fridge depends on when we last went to the store. <img src="/images/graemlins/wink.gif" alt="" />
Also, we keep a lot of ice in the deep freeze that could be used as it melts.
Look for "hidden" water now and tuck that knowledge away for later.