Life Expectancy in the Desert

Life expectancy depends upon the water available and your ability to protect the body from exposure to the sun to minimize perspiration. Allow a slight negative balance. Drink 1.5 liters (2½pt) for every 2 liters (3½pt) lost and then drink at the rate the body is sweating. Efficiency is then impaired little and no water is wasted. Less fluid will not result in less sweating. Sweating is a cooling mechanism, not a way of losing moisture. If drink more fluid than needed it will
be excreted and used to no purpose.

Without water you will last about 2½ days at 48°C (118°F) if you spend the whole time resting in the shade, though you could last as long as 12 days if the temperature stays below 21°C (70°F).

If you are forced to walk to safety, the distance you cover will relate directly to water available. With none, a temperature of 48°C (118°F), walking only at night, resting all day, you could cover 40km (25 miles). Attempting to walk by day you would be lucky to complete 8km (5 miles) before you collapse. At the same temperature, with about 2 liters (3½pt) of water you might cover 56km (35 miles) and last 3 days. Your chances are not appreciably increased until available water reaches about 4.5 liters (8pt) per person, though training and a determination to survive could contradict predictions.