One of the most fundamental rules of survival is water. You won’t last long without it. Your chances will be significantly diminished if you drink water with chemical or biological contamination. Even wild water in the mountains may have giardias which causes severe intestinal distress and further loss of fluids. Some filtration systems take care of this but they’re all not very compact. Iodine filter straws and ozone tablets kill bacteria, but don’t take out chemical contaminants. I carry one of those straws in my Ranger-7 sheath, and the components of a Solar Still. It’s a 44″ square piece of very thin plastic like a dry cleaner bag, and a folded Dixie cup, that’s it, fits neatly away in back of the kydex liner of the Ranger sheath, weighs next to nothing. It’s cheap and effective, but requires some patience and forethought to get results (water). You can produce pure, clean water for survival, even in the desert, using this lightweight, compact, simple, fundamental technology of a Solar Still. For situations where there is no standing or flowing water, the Solar Still will distil water from soil, plant material, even urine.
To set up a Solar Still, choose a sunny location, preferably near shade where you can sit out the hottest part of the day. Using the back of the Ranger-7 knife, I dig out a conical hole about a foot and a half deep and two feet across. Gather plant materials to put in the bottom of the hole. Cactus is a very good source of water, releases more if it is chopped up to expose more surface area to evaporation. You can even urinate in the hole for more water. Next, place the Dixie cup upright in the center of the hole and cover with the light plastic sheet. Place a small stone in the center of the sheet so that the sheet forms a cone with the lowest point directly above the Dixie cup, pile dirt around the edges to seal the cover.
Find a place out of the sun or set up a shelter with the survival blanket and paracord from the front pocket of the Ranger sheath. Relax and be patient as the heat of the sun evaporates moisture in the hole to condense on the plastic sheet and drip down into the Dixie cup. After several hours, there will be pure, distilled water in the Dixie cup. I carry a gallon plastic zip-loc bag in the ranger sheath to use as a canteen, strap this to my belt with paracord, and continue on my way, in the cooler part of the day, with a fresh supply of water.