Dehydration

“Dig your well before you are thirsty.” - Proverb

The third rule in the Rule of Threes is that you can survive only three days without water. Recall that the rule for shelter was just three hours. Ideally a good shelter will also provide water nearby. If you become weak or ill in the wilderness, you don't want a long or difficult hike to water. It may be necessary to build a few temporary shelters before finding the perfect location. Future posts will cover ways to find water and how to make water traps to catch dew and rain water.

The human body is 75% water which is constantly being depleted by breathing, sweating, menstruation, digestion and urination. Dehydration occurs when you consume/drink less fluid then you emit. Mild dehydration begins when you lose about 2% of your body water. For a 200 pound person this is 3 lbs of water or 1.5 quarts. Fluid loss can be quite rapid with vomiting and diarrhea - two possible symptoms if you're eating strange plants when lost. It is far better to remain hungry than to acquire food poisoning wilderness.

Environment and Water Needs

Surprisingly, very cold environments can be as dry as the driest desert. Cold air cannot hold much moisture; it drys your body with every breath you take. Cold dry air also robs your body of moisture from exposed skin - for example: chapped lips. You may become severely dehydrated without even realizing the danger you are in.

Wind also play a role in dehydration. A dry wind on exposed flesh can suck the water right out of a person. The remains of mummified animals and people are often found in desert regions, their bodies totally dried out.

Symptoms
See http://www.symptomsofdehydration.com/ for a detailed list of symptoms at increasing stages of dehydration. Muscle cramps can occur with 5% loss of body fluids. Dehydration becomes deadly at 10% fluid loss with seizures and loss of consciousness.
If the patient becomes confused or lethargic; if there is persistent, uncontrolled fever, vomiting, or diarrhea; contact a doctor.

Treatment

• Drinking fluids is usually sufficient for mild dehydration. It is better to have frequent, small amounts of fluid (using a teaspoon for an infant or child). Drinking too much fluid at once can bring on vomiting.
• Electrolyte solutions or freezer pops are especially effective. These are available at pharmacies. Consider also clear broths and jello. Sport drinks contain a lot of sugar and can cause or worsen diarrhea. For infants and children, avoid using water as the primary replacement fluid.
• Intravenous fluids and hospitalization may be necessary for moderate to severe dehydration. The doctor will try to identify and then treat the cause of the dehydration.

The Mayo Clinic has recommendations on preventing dehydration.

Bottom Line
As discussed in the last two posts, dehydration increases the risk of Heat Stroke in hot/humid weather. Heat Stroke will kill you faster than dehydration - hence the importance of establishing shelter before water. Don't kill yourself searching for water.

Additional Sources
http://www.medicinenet.com/dehydration/article.htm
http://www.nlm.nih.gov/medlineplus/ency/article/000982.htm
http://www.mayoclinic.com/health/dehydration/DS00561