In desert areas available water often contains salt, or other minerals. It may also contain pollutants or organisms such as blue-green algae which make it unsafe to drink. Salt in excess of body requirements can be eliminated only by increasing the water intake. This explains why salty water is undrinkable. In practice, the salt content of water must be below 1% if the water is to be drinkable. If it happens to rain, a large sheet of thin polythene (e.g. 4 × 2 m) is useful. It can be put out to catch the rain, and can yield several litres from a millimetre of rain. A sponge is useful for collecting the water. Issues of safe drinking water are discussed in Chapter 28.
Even though the nights in the desert can be cold, dew usually occurs only for a few nights following rain. Dew can be collected from some tents by turning up the eaves with sticks to form a shallow gutter around the tent roof and then either sopping it up with a sponge, or scraping it into the gutter with the blade of a knife. A two man tent will yield a cup of water (flavoured with proofing). Another method of collecting dew is to spread a plastic sheet on the ground.
Water from bush dams and soaks is often polluted by animals so purification is therefore essential, as described in Chapter 28. The appearance of muddy water can be improved by letting it settle overnight in a billy or water bag, or by adding a piece of charcoal. The taste of stagnant water may be improved by aeration, e.g. by whisking it with a twig or by pouring if from container to container. Encourage members of your party to drink freely and copiously from the time they arrive at camp until they leave, especially in the morning, and then to drink little and often during the day. A salt and mineral replacement may be required, particularly by people with a high salt intake in their diets and who are unaccustomed to heavy sweating in hot, dry conditions. One level teaspoon of Staminade (or similar product) per litre of water is sufficient.