Your body, like the Earth, consists of mostly water. A widely accepted fact is that most folks cannot live much longer than 2 days without water. The experts generally recommend for the average person a minimum of eight 8 ounce glasses of water per day. Accordingly, you will need to provide one half gallon of water per person per day at a minimum. This amount actually varies from person to person by environmental temperature, body mass, and level of exertion.
The following web link contains a calculator which can be used to obtain rough estimates for a given body’s daily water needs.
Human Water Requirements by Body Weight and Exertion Time
When creating your 72-hour plan, you need to estimate how much water you and those included in your plan will need. There are many ways to address your water needs during the first 72-hours of a casualty. These can involve stored water supplies, portable water purifiers, short-term distillation methods, or a combination of these methods. As your preparedness deepens, you will eventually need to think and plan beyond the initial 72-hour period. These plans may involve fixed purification systems, reverse osmosis, filtration systems, rain water collection, well construction, etc. The goal is to identify, source, and have access to, clean drinking water every day.