Guide to Wilderness Survival/Obtaining Water
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Water is an essential item on any camping or hiking trip. Some campgrounds have tap water, drawn from wells and purified. This water is of reliable quality under normal circumstances and should be used whenever practical. When tap water is not available, it is usually best to bring all necessary water from home. However, it is impossible to bring more than a couple of days' worth of water on a backpacking trip, and survival situations may create an unforeseen demand for water. If this demand is not met, dehydration will result, leading to heat exhaustion, heatstroke and death within days. Please avoid the thought of rationing water. The best storage container in a survival situation is your own body. Even experienced soldiers have been found dead of dehydration with a full canteen.
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[edit] If a natural water source is available
It is not difficult to obtain water from a natural body of fresh water such as a river or lake, but this water should not be used untreated. Natural water often contains organisms that cause infectious disease, most notably Giardia lamblia. There are four ways to remove this threat and make natural water potable.
- Water may be boiled over a campfire or portable stove. At high altitudes, water boils at a lower temperature, so the boil must be maintained for several minutes to kill the microorganisms.
- Water may be filtered with a portable water purification device. Water purifiers differ widely, so if you own one, familiarize yourself with the instruction manual. If the water is visibly dirty, pour it through a clean cloth to remove large particles and avoid prematurely clogging the purifier.
- Certain chemicals, such as dilute chlorine solution, are commercially sold as antimicrobial additives. Some leave an unpleasant flavor that may be masked with powdered drink mix.
- Water may be added to an evaporation still or solar still to purify the water through the natural evaporative process. Questionable water is added then when it evaporates it rises and condenses on a cooler surface. It then drips into your collection container where it can be collected using tubing to maintain the efficiency of your still. The warmer the still becomes the faster you will be able to collect pure water. Only a few chemicals will evaporate with the water one of which is benzene. This is usually only a concern when trying to purify flood waters.
This method can also be used to purify salt water. As long as the salt water is not allowed to get on your collection surface or in your collection container the water will be potable.
[edit] If a natural water source is not available
[edit] The evaporation still
Water may also be obtained from the soil or from plant matter.
Probably the best way to get water from the ground is the evaporation still, shown in cross-section in the diagram at right. To build an evaporation still, you need only four items: a shovel, a sturdy sheet of transparent plastic, a cup, and a piece of flexible plastic tubing long enough to reach from the middle of the plastic sheet to the side with some excess length.
Begin by digging a hole with sloping sides in the shape of the sheet of plastic, but slightly smaller. Avoid digging in hot weather, as you will lose considerable amounts of water through sweat. Sink the cup in the middle of the hole so that the rim is almost flush with the sides of the hole. Place one end of the tube in the cup, run the other end to the outside of the hole, and place the sheet of plastic over the whole assembly. Weigh down the sides of the plastic sheet, or anchor them with stakes, and place a small weight directly over the cup.
The evaporation still will produce water continuously. The plastic sheet will create a greenhouse effect in the still, accelerating the natural evaporation of water from the soil. When the water vapor hits the plastic sheet, it will condense and drip down into the cup. The tubing may be used to drink from the cup without disturbing the still. For added effectiveness, use a second cup to pour any available water-based fluids, such as urine or water collected from roofing or tent surfaces into the pit. A second tube would also work for this same purpose.
[edit] The vegetation still
An easier method uses just a plastic bag. Gather enough succulent vegetation (big leaves, cacti stripped of their thorns, etc.) to mostly fill the bag. Mash it to break through the leaves' outer water-resistant cuticle. As in the evaporation still, a greenhouse effect will cause water to evaporate from the leaves. It will then condense on the plastic and run down into the bottom of the bag.
The water in the bag will pick up chemicals from the leaves. These will give it a strong leafy flavor, and may include toxins, so make sure not to gather any poisonous plants.
Vegetation may also be added to an evaporative still to avoid the unpleasant taste but the used vegetation will have to be cleared out after the water has been collected from it. Preferably at night when the still is less effective.
