Having an ample supply of clean water is a top priority in an emergency. A normally active person needs to drink at least two quarts of water each day.
Hot environments can double that amount.
Children, nursing mothers and ill people will need even more. You will also need water for food preparation and hygiene. You should store at least a two-week supply of water for each member of your family. If supplies run low, never ration water. Drink the amount you need today, and try to find more tomorrow.