You can use stills in various areas of the world. They draw moisture from the ground and from plant material. You need certain materials to build a still, and you need time to let it collect the water. It takes about 24 hours to get 0.5 to 1 liter of water.

To make a belowground still, you need a digging tool, a container, a clear plastic sheet, a drinking tube, and a rock (Figure 6-7).

Select a site where you believe the soil will contain moisture (such as a dry stream bed or a low spot where rainwater has collected). The soil at this site should be easy to dig, and sunlight must hit the site most of the day.

To construct the still–

• Dig a bowl-shaped hole about 1 meter across and 60 centimeters deep.
• Dig a sump in the center of the hole. The sump’s depth and perimeter will depend on the size of the container that you have to place in it. The bottom of the sump should allow the container to stand upright.
• Anchor the tubing to the container’s bottom by forming a loose overhand knot in the tubing.
• Place the container upright in the sump.
• Extend the unanchored end of the tubing up, over, and beyond the lip of the hole.
• Place the plastic sheet over the hole, covering its edges with soil to hold it in place.
• Place a rock in the center of the plastic sheet.
• Lower the plastic sheet into the hole until it is about 40 centimeters below ground level. It now forms an inverted cone with the rock at its apex. Make sure that the cone’s apex is directly over your container. Also make sure the plastic cone does not touch the sides of the hole because the earth will absorb the condensed water.
• Put more soil on the edges of the plastic to hold it securely in place and to prevent the loss of moisture.
• Plug the tube when not in use so that the moisture will not evaporate.

You can drink water without disturbing the still by using the tube as a straw.

You may want to use plants in the hole as a moisture source. If so, dig out additional soil from the sides of the hole to form a slope on which to place the plants. Then proceed as above.

If polluted water is your only moisture source, dig a small trough outside the hole about 25 centimeters from the still’s lip (Figure 6-8). Dig the trough about 25 centimeters deep and 8 centimeters wide. Pour the polluted water in the trough. Be sure you do not spill any polluted water around the rim of the hole where the plastic sheet touches the soil. The trough holds the polluted water and the soil filters it as the still draws it. The water then condenses on the plastic and drains into the container. This process works extremely well when your only water source is salt water.

You will need at least three stills to meet your individual daily water intake needs.

Read how to make an aboveground still here.