When the well is dry, we know the worth of water.
– Benjamin Franklin, Poor Richard’s Almanac

The Danger of Dehydration
So you’re four or five miles down the trail and you’ve been better. The day started off nice enough – birds singing, beams of sunshine coming through the trees, all was right with the world. Now, it’s several hours later, the day has turned hot and humid and the trek is tougher than you thought it would be.

Your shirt is soaked with sweat, your head hurts, you find yourself frequently tripping over rocks, you’re weary and irritable. What to do? Stop, rest and drink. You’re probably dehydrated. Dehydration can sneak up on any of us, at any time. It’s more acute in extreme weather, either heat or cold, but can happen in any climate. The Rule of Three suggests that a person can live for three days without water but that’s only a guideline. The truth is that in a hot, arid climate, dehydration can turn fatal in as little as one day. And, in a cold climate, dehydration intensifies the onset and severity of hypothermia.

An Essential Element
Water is essential to human life. Every bodily system we have depends on it to function properly. Our bodies are constantly using water to digest food, regulate our temperature, lubricate joints and filter blood along with many other critical tasks. Yet, every time that we breathe, we lose water.

Drinking water is the single best thing that you can do to maintain top form in the outdoors. Even slight to moderate dehydration will result in decreased physical performance, headaches, irritability, decreased mental capacity and reduced heat regulation. Drink early and often. Drink like your life depends on it, because it does.

How Much is Enough?
Try to pre-hydrate, that is, drink water before you start an activity. One half to one liter of water is a good start, then drink small amounts often throughout the activity. Don’t rely on a feeling of thirst to drink. Make it a habit. If you aren’t watering the weeds regularly and your urine isn’t mostly clear, you aren’t drinking enough water. There isn’t an exact formula to determine how much water a person needs. There are just too many variables – exertion levels, climate and body mass to name a few. But, most expert opinions seem to fall within this range:

One to two liters per day just to replace water lost to normal body functions.
Two to four liters per day to maintain hydration during moderate activity.
Four to eight liters per day to maintain hydration during strenuous exertion.
The dry air common to high altitudes will also exacerbate dehydration. Even normal respiration while at rest in this environment results in a significant amount of lost water.

It is possible to drink too much water, a condition known as hyponatremia. This is a condition where a normal level of sodium in the blood is lowered to a dangerous level by the combination of sweating and excessive water intake. The common sense approach to preventing this is to eat some salty snacks when engaged in activity that produces heavy perspiration and perhaps including the occasional sports drink with your water.

If You Are Lost
In a survival situation you should drink water even if you cannot purify it. Dehydration is a more immediate threat to your life than Giardia or other diseases. However, it makes sense to use the safest water possible. Rainwater is considered safe everywhere, with the possible rare exception of the acid rain around active volcanoes. Use a Heatsheet or similar survival blanket to funnel rainwater into a container. Super absorbent, micro-fiber towels are not only useful to for drying yourself off, they can also be an effective way to collect dew from grass and leaves or soak up water from an otherwise inaccessible pool. Melted fresh snow is generally safe to drink although you might be astonished at how much snow it takes to make one cup of water. If you are getting your water from streams or rivers, acquire it from the clearest, fastest moving section that’s available.

Remember the adage “ration sweat not water”. If you are in an emergency situation don’t ration your water excessively. Sip it slowly and regularly throughout the day. It’s surprising how many people have died from dehydration with water left in a canteen. Try to work slowly during the coolest time of the day and rest during the heat of the day. You don’t want to lose water by sweating. Also, it’s important to avoid eating unless you have adequate water. Digestion requires water and will intensify dehydration.

In Conclusion
Dehydration is a condition to take seriously. Its stealthy approach can catch us by surprise and the effects are perilous. Mild dehydration can cause poor decision making and unsure trekking. Severe dehydration can cause hallucinations and death. Stay safe and healthy – drink up.