Published: February 2007
Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

It can be a challenge to find the water needed during a long ramble through the desert. Natives such as the roadrunner or the kangaroo rat have finely tuned mechanisms for extracting water from their food and conserving it in their bodies. Human hikers aren't as lucky and have to pack in the water they need or get creative looking for it.

Solar stills can be used to condense moisture by placing a plastic sheet over a large hole. But some survivalists are skeptical, pointing out that the stills can be unreliable and a thirsty traveler can sweat away lots of water setting them up. Clear plastic transpiration bags tied around nonpoisonous plant branches take less energy to set up, but don't produce much water. Bringing along a good supply and limiting activity during the hottest times of the day are likely to be a trekker's best bets, but the desert does offer some clues for locating water in an emergency.

Animals can help, as many will seek out watering holes early and late in the day. A horse may lead you to water, but donkeys are even better at sniffing it out. Certain vegetation such as the cottonwood may be a sign that water is available near the surface. Even landforms can steer you to quiet springs or water just below the ground. Try digging along the outside edge of bend in a dry riverbed or looking where greenery is present at the base of a hill or ridge of stratified rock. Regardless of how you find it, purifying any wilderness water is always a good idea.

—Brad Scriber