If you are headed into the desert, or any area in which water is scarce, knowing how to make a solar still is an important skill to have. The concept is simple, and the equipment needed can easily fit into a day pack or small emergency kit.

All you need is a six-by-six-foot sheet of clear or milky plastic, a container to catch the water, and a six-foot piece of tubing.

Dig a hole about three feet deep and three feet wide. Try to dig the hole in a damp or low area, such as a gully or dry creek bed. In drier areas, a deeper hole might be needed. At the bottom and center of the hole, place the container to catch the water. Run the tubing from the container up and over the side of the hole. This way you don’t have to break down the still to get a drink, but can simply suck on the tube when you are thirsty.

Now put the plastic sheet over the hole, weighing down the sides with rocks and dirt. Put a rock in the center of the sheet so that it makes a cone shape, with the center right over the container, but no higher than three inches.

A solar still works by creating a greenhouse effect under the plastic. As groundwater evaporates it collects on the underside of the plastic, until it runs down and into the container. Solar stills made in damp areas can collect water up to five days, and then they should be moved to a different location.

Stills located in drier areas should be moved every two or three days.

Remember that this is a survival skill and should only be used in survival situations. Natural landscape can quickly become marred if every one started digging solar stills. At the same time, it’s always good to practice skills before you are in a situation in which your life depends on it.

So make a solar still in your back yard, and have fun with it. Notice how much water it brings in, how quickly it does it. Take note of how much sun it gets and see how that compares to when it’s in the shade.

When you do go out on an outdoor adventure, always tell someone where you will be going and when you will be back. Set a time at which if you haven’t arrived, that person can start either looking for you, or call for help.

And always bring plenty of water. As a general rule, try to bring twice as much water as you think you’ll need. Yes, it’s heavy, but it will keep you alive.