8 ga of water per person per day is completely insane in disaster scenario. 2-3ga for drinking a day? Medical professionals recommend less than 1 for a normal person.
Figuring 5gal/d as a lower bound for daily consumption in an emergency sounds wrong. This is a situation where you need enough water not to die, which mostly means enough water to drink and a little bit for critical sanitation. The standard recommendation is a fifth of that: "one gallon per person per day" -- https://www.ready.gov/kit
About 8.5 gallons per day or 32 liters. A few gallons per day in an emergency is plenty for drinking, cooking and hygiene so 4x that much is a good start.
If you drink ~19 litres (5 US gallons?) of water every day you will not survive long. That’s about an order of magnitude more than is recommended under normal non-strenuous conditions.
> 8 gallons per person per day. Water is heavy—8 pounds per gallon
The average person needs far less than 65lbs (30kg) of water per day, which is a third of the average male weight in the US.
By medical standards humans need more like 8lbs (under 4l) per day for men and 6lbs (under 3l) for women. Less if your rationing and not exerting yourself.
Just remember, 8 cups of water a day is a myth. It has no scientific basis[0].
It was the result of misunderstanding a 1945 study that spread around like wildfire (since people realised they weren't drinking 8 cups, and tried to). The figure includes water contained within food, which is a significant amount. If you're drinking 8 cups AND consuming a normal diet you may be drinking too much (assuming moderate weather conditions and no underlying medical problems leaving you dehydrated).
The vast vast vast majority of people drink way too little water. I drink a little over a gallon a day in addition to the occasional coffee or soda and still occasionally feel the effects of dehydration. I know people who may only have 2-3 glasses of water in a day and nothing else. It's crazy they're still alive.
My experience at Burning Man is that 8 liters per day per person is a more usual rate of consumption, because you need water not just for drinking, but also for cooking food, washing dishes, washing your body, washing your hands, and washing wounds.
The .6 kg/hr/person figure for water is pretty generous - that works out to 3.8 gallons/day/person. As any burner could tell you, you only really need about 1 gallon of water per day for survival. Spending 2.8 gallons per day on hygiene is quite luxurious when you consider that you have to crack that water out of regolith. Taking a 1-gallon sponge bath once a week and drinking the rest would cut it to < .2 kg/hr/person - before reclamation!
In 1945 there was a recommendation that a healthy adult should have about 2.5 liters of water intake a day, including water that is part of the food you eat.
Somehow the media managed to drop the last part, and recommended you drink at least 2l water a day. Or even more.
I think drinking 2-3 liters of water per day (~100 ounces?) is seen as beneficial for the health. People usually don't drink that much because they don't feel thirsty, but they would like to.
I don't live in the US so I don't know what I'm talking about.
"Adequate Intakes (AI) have been defined derived from a combination of observed intakes in population groups with desirable osmolarity values of urine and desirable water volumes per energy unit consumed. The reference values for total water intake include water from drinking water, beverages of all kind, and from food moisture and only apply to conditions of moderate environmental temperature and moderate physical activity levels (PAL 1.6). [...] Available data for adults permit the definition of AIs as 2.0 L/day (P 95 3.1 L) for females and 2.5 L/day (P95 4.0 L) for males."
"The minimum water requirement for fluid replacement for a 70kg human in a temperate zone equates to 3L per day, or 42.9mL/kg [according to the Tropical Agriculture Association]. Minimum requirements for an individual the same size but in a tropical zone equates to 4.1 to 6L/day"
"Age and gender specific Adequate Intakes (AI) for water were established in 2004 by the [United States] Food and Nutrition Board (5). The Dietary Reference Intakes (DRI) for water are [for ages 19 and older] Men 3.7 L/day Women 2.7 L/day"
reply