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Your second consideration to surviving in the wilderness, after shelter, should be water. The presence of water is going to determine where you put your camp site. How important is it to drink lots of water?
(Some of the following information from the Camelbak web site.)
DEHYDRATION: People just naturally assume that their thirst mechanism will protect them from dehydration. That if they become dehydrated, it will tell them by triggering intense thirst until they are properly hydrated. But this isn't always the case. It is possible to lose fluid so quickly that the normal thirst mechanism is overwhelmed. The sources of fluid loss are respiration, perspiration, urination and defecation. The rate of loss from each of these will vary according to activity levels, air temperature, humidity and altitude.
RESPIRATION: With normal daily activities you will lose approximately one to two liters of water via evaporation from the lungs. As you breathe, the air that you inhale is "conditioned" – it is warmed to 98.6F and humidified to 100% humidity. This warm, moist air is then exhaled and the cycle starts over again. In extreme cold and high altitude, water loss through respiration can be up to one cup per hour, or six liters in 24 hours.
PERSPIRATION: People think of sweat in terms of perspiration at the armpits or upper lip. Truth is that all of your skin sweats during activity, even though cotton clothes may absorb it or bare skin such as arms in short sleeves will lose it directly to the air. With normal daily activities you may perspire from one to two liters per day. But with exertion in hot, dry weather, sweat loss can become extreme. During heavy exertion, you can lose one to three liters of water per hour, which can amount to 8-10 liters of fluid over an afternoon.
URINATION: One to two liters of fluid are lost daily through urination – a natural clearing of waste products from the blood. The amount of urine produced will increase with over-hydration and decrease with dehydration.
DEFECATION: The average daily loss of fluid through defecation is only about 0.1 liter. However, this can increase dramatically with diarrhea.
Through the activities of daily living, the average day's loss of fluid is four liters, which is generally replaced by the fluid you drink and the food you eat. But the amount of fluid required can be significantly increased by exercise, sweating, diarrhea, temperature or altitude. The most common cause of increased fluid loss is sweating.
Q. Do people really need to be concerned with hydration?
A. Definitely. Becoming dehydrated is deceptively simple because water loss is masked by several factors. Altitude, wind, temperature and even the clothes you wear can trick you into thinking you don't need to rehydrate. It's surprising how quickly your body uses water and how it affects you. Losing 2% of your body's weight in water – that's about 3 pounds for a 150 pound person – is enough to start feeling the initial effects of dehydration: decreased energy and endurance. It's also worth remembering that those who work out casually or occasionally are more prone to dehydration, since their bodies are less acclimated to exercise.
Q. OK, so I can become dehydrated. How will it affect me?
A. The two biggest effects are loss of energy and endurance. Staying properly hydrated will keep your energy level higher so you can perform your duties better, keeping you alert and focused on the mission at hand. When you are dehydrated your body has less sweat to cool your system, so you feel hotter and less comfortable. Eventually you will experience the headaches, nausea, and fatigue associated with the higher levels of dehydration. Staying properly hydrated will also help you feel better the day after hard training.
Q. Yikes! So how soon can I become dehydrated?
A. Just a 2% loss in body weight due to dehydration is enough to elevate your body temperature. Which means you ill feel initial effects of dehydration by the end of an hour on a hot day, after two hours you will be feeling weaker and may experience cramping. Nausea, headaches, serious fatigue and other physical symptoms associated with heat exhaustion can set in within 3-4 hours.
Q. How often should I drink?
A. As often as possible. Research has shown that athletes who continually sip water, versus inconsistent gulping, stay far better hydrated. In a 1997 study, cyclists using CamelBak hydration systems drank 46% more fluids during a century ride, 152% more while actually riding, than water bottle users. That's because the CamelBak cyclists had easy access and a convenient method of obtaining fluids. This study applies to you, too!
Q. And how much should I drink?
A. As a rule, you should try to drink 8 ounces of fluid every 15 minutes. Since your body can only absorb about 1 liter of water per hour you need to carry at least that amount for every hour you engage in serious physical activity. Anything over a liter will be "processed" immediately, (you'll need to pee.)
Q. Seems like a lot of water. Do I really need that much?
A. Again, you need a liter per hour. For one hour, that translates into a 40 ounce CamelBak's worth. For two hours, you need two liters, or one 70 ounce CamelBak. Three hours of exercise needs three liters of fluid, or a 100 ounce CamelBak system. So, yes, you do need that much.
Another backpack water system maker puts it simply- HYDRATE OR DIE!
Q. So how do I find water in the wilderness?
A. This is an important question. First, observe the animal trails. Where two trails meet in a V, the bottom of the V is almost always pointed in the direction of the trail leading to water. You can also watch small flocks of birds in the late afternoon, as they will water before they roost. Water is always going to be downhill, in the Vs of the mountains. When searching for water, notice the green vegitation with broad, floppy leaves. These can be a key to finding water.
You are going to have to be a detective here and explore your area. Water shown on a Topo map may be seasonal or even have dried up completely as most Topo maps are badly dated.
When you do finally locate a clear, cold spring, that spring becomes yours and it is really rewarding.
But don't start slurping it down just yet!...
That wilderness water should be treated or else you could seriously compromise your health by injesting parasites such as giardia, bacteria, or even viruses such as hepatitus.
The 3 ways to purify water are by boiling, condensing, (as in a transpiration bag, or *cough-bad method- solar still,) and chemical treatment.
Transpiration from a tree.
Ranger Rick has tips on filtering and purifying water.
