Dehydration becomes increasingly noticeable as more body fluid is lost. Water makes up 75% of the body weight -- about 50 liters (11 gallons) for the average man. Survival is unlikely if more that one fifth of this is lost!
Fluid loss 1-5%: Thirst, vague discomfort, lack of appetite, flushed skin, impatience, sleepiness, nausea.
Fluid loss 6-10%: Dizziness, headache, labored breathing, no salivation, indistinct speech, unable to walk.
Fluid loss 11-20%: Delirium, swollen tongue, unable to swallow, dim vision, numb and shriveled skin.
In latter stages: There is gross muscular weakness and mental capacity is impaired -- you must make your plans at the start when you can think clearly --- then stick with it.
