Here are a few of the more common myths that show up in survival literature and that we address during our fieldcourses.
Water From a Barrel CactusThe notion of slicing open a juicy barrel cactus and scooping out a cup of water to quench your thirst sounds appealing. The problem is that, due to the alkaloids present in the cactus, most people experience severe cramping and vomiting, which only increases their dehydration.
Furthermore, the amount of moisture found in a barrel cactus depends on seasonal rainfall. Assuming that you have the tools (i.e., machete, tire-iron, etc...) to cut into the spiny cactus without injuring yourself, you have just killed a succulent that may be over one hundred years old not to mention protected by law.
The few times I have had the pleasure of choking down barrel cactus fluid (notice I didn't say "water") made my stomach churn like a cement-mixer and required a Buddhist's monks meditative effort at keeping from vomiting. Like I tell my students- there's a reason why you don't see "Cactus Juice" sold at the grocery store!
Save the romantic notions for the Hollywood westerns and rely on this method only if there is no other alternative. By the way, the only barrel cactus that isn't toxic is the fishhook barrel (Ferocactus wislizeni).
Collecting Water With a Solar Still
The solar still involves digging a two foot deep pit with a three foot diameter, placing a container in the bottom, and covering the whole pit with a six foot by six foot piece of clear plastic. The plastic
condenses ground moisture on the interior covering where it funnels down to the center and drops into the container.
Constructing a still involves expending considerable amounts of your precious sweat to dig the pit. It also presupposes that you have a sheet of clear plastic and a shovel. If you had the foresight to bring this gear then you probably had the good sense to pack plenty of water. The solar still just isn't that useful in the desert and yet it still shows up in survival books as a reliable water-collecting device.