Safe water - Version 1.0 When you're in a wilderness survival situation you need to drink water. The more active you are, and the hotter it is, the more water is needed. The average person needs about two liters of water per day which weighs just over 4 lbs. If you are going to be gone for a week, you would have to carry 28 lbs of water. If you want to travel light, this will not work. Can you drink from a clear mountain stream? You could, but you might become very sick, because of organisms in the water. It is better to sterilize the water before drinking it.Water is by far the most important nutrient for the human body, besides oxygen. In a survival situation finding drinking water will not be easy. The question is how long can the human body survive without water? How long can you survive without water depends on the temperature, your physical activity and your physical condition. At 120F, you can survive for two days without water, and at 70F, you can survive for 10 days without water if you stay in the shade. A minimum of