Table of contents 1 If a natural water source is available
2 If a natural water source is not available
2.1 The evaporation still
2.2 The vegetation still

If a natural water source is available

• 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 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.

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

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.

The scale was initially developed as the Sierra Club grading system in the 1930s to rate hikes and climbs in the Sierra Nevada range. Previously, hikes and climbs were described relative to others ("harder than X, but easier than Y"), but this made it difficult for those who hadn't done the other hikes or climbs to understand the comparison, so the numerical grading system was an attempt to codify this into a single scale.

Currently, according to the climbing textbook Mountaineering: The Freedom of the Hills, the system divides all hikes and climbs into five classes:

• Class 1: Hiking.
• Class 2: Simple scrambling, with possible occasional use of the hands.
• Class 3: Scrambling, a rope can be carried but is usually not required.
• Class 4: Simple climbing, with exposure. A rope is often used. Natural protection can be easily found. Falls may well be fatal.
• Class 5: Technical free climbing. Climbing involves rope, belaying, and other protection hardware for safety.

Note that the exact definition of the classes is somewhat controversial [1].

The increasing technical difficulty of Class 5 climbs led to the same "relative grading" problem that had caused the initial development of the system, so that class was subdivided in the 1950s. Initially it was based on ten climbs in Taquitz, California, and ran from "The Trough" at 5.0, a relatively modest technical climb, to "The Open Book" at 5.9, considered at the time the most difficult unaided climb humanly possible. However, advances in techniques and equipment have since led to harder climbs being completed. The first such climb was given the rating 5.10; the second the rating 5.11. It was later determined that the 5.11 climb was much harder than 5.10, leaving many climbs of varying difficulty bunched up at 5.10. To solve this, the scale has been further subdivided above the 5.9 mark with a-d suffixes. It is now an open-ended scale, with 5.15a the hardest climb having been completed (as of October 2003).

Reference and Source