Besides Shelter, water is the most important preparaton that you need to plan. The standard is that you prepare for using one gallon a day, however that rule takes into account hygiene, If we are talking strictly about water consumption, then you can get by with less.
To stay healthy, you need to continually replenish your water supply. Experts recommend drinking approximately two quarts (64 ounces or about eight glasses) of water each day. Of course, if you are in an extremely hot or cold area — or if you are moving a lot — you may need to drink a gallon or more of water every day..