|Table of contents|
2 If a natural water source is not available
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 may not be used immediately. Natural water often contains organisms that cause infectious disease, most notably Giardia lamblia. There are three ways to remove this threat and make natural water potable.
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 fluids, such as urine, into the pit.
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.