Regarding the question about how much water do we actually need, the
following is taken from Sally Fallon's book "Nourishing Traditions":

How much water should we drink? Conventional wisdom calls for six to
eight
large glasses per day, but Oriental medicine teaches that this a
dangerous
practice which puts undue strain on the kidneys.  The food we eat
contains
a great deal of water and water is also a by-product of carbohydrate
metabolism.  There is some evidence that an additional six to eight
glasses
of water can lead to mineral losses. Researchers from both East and
West
warn that excessive liquids taken at meals dilute stomach acid and put
undue strain on the digestive process. A good rule is to avoid
drinking
large amounts of liquid from one half hour before a meal to two hours
after. It is also wise to avoid liquids that are too hot or too cold.
Iced
water with a meal makes digestion very difficult.

Binnie