Even in cool weather, you need two to four quarts of water a day. Under most conditions, humans can only last about three days without water.
- Pure drinking water is rare, even in the most remote regions. Clear mountain streams often are contaminated by Giardia lamblia, a parasite that causes serious intestinal sickness in humans.
- The best way to purify water is by boiling. Chemical purifiers such as iodide/iodine or chlorine and filter systems can be used, but some may not be satisfactory. Never make survival problems worse by drinking unsafe water.