Well, I don't have much idea what the average american uses, but it is
easy to live on way less than 70 gallons per day. One can get by on
about 5 gallons, maybe 10 gallons, a day. That includes drinking,
cooking, cleaning, washing clothes (by hand, which admitedly uses a lot
less water), the occational sponge bath once a week or so, and re-using
waste water for flushing the toilet.

A quick check on
http://www.peacecorps.gov/WWS/water/...eog01sup01.pdf
shows that 10 gallons per day per capita is about average for w.
africa. US is closer to 200 gallons per day per capita. But in an
emergency, one has to learn to change lifestyles quick.