Hiking equipment
According to Tom Brown, the basic plan for survival is in the order of shelter (including clothing), water, fire, and food. Cody Lundin writes about the "Rule of 3s"; this relates to human survival without basics: three minutes without air, three hours without shelter, three days without water, or three weeks without food.
Drinking water
The amount of drinking water required is variable. It depends on physical activity, age, health, and environmental conditions. In a temperate climate under normal conditions, adequate water intake is about for adult women and for adult men. Physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake. Physically active individuals in hot climates may have total daily water needs of or more. The European Food Safety Authority recommends per day for adult women and per day for adult men.