How Much Water Is Enough During a Disaster?

The experts tell us to pack enough water, gear, and supplies to survive for 72 hours (3 days) in the aftermath of some natural or man-made calamity. The reality is that you should be prepared to be self-sufficient for much longer than 72 hours. Responders might not be able to reach the hardest-hit areas of a disaster for at least a week or two.

It's important to have what you need to go it alone for as long as 14 days. Some folks may find it hard to estimate how much stuff that really is. Take water, for example: how much do you really need in a disaster? Let's do the math based on what the experts say is the minimum. This works for longer periods, too.

Authorities suggest keeping at least a 3-day supply of water on hand in case of a disaster. The common definition of a 3-day supply is 3 gallons per person—a gallon per person, per day—half to drink and a half to use for cooking and sanitation. The Centers for Disease Control and Prevention (CDC) even recommends drinking your half-gallon every day during an emergency, no matter what. In hot weather, or for special cases like pregnancy or illness, the CDC recommends drinking closer to a gallon per day.

Water jugs
Raja Islam / Getty Images

Don't Ration Your Water

Most experts, including the CDC, warn against rationing. Drink it and more will come, they say. It's true that we shouldn't ration water supplies in a disaster, but you also may not need to force yourself to drink. There's a difference between depriving yourself of water in order to save it for later versus just not drinking all of it because you're simply not thirsty.

While not expressly stated, the suggestion to drink at least 64 ounces of water every day during a disaster comes from a longstanding myth that people need to drink eight glasses of water (a glass is defined as 8 ounces) regardless of whether they've had anything else to drink or not. In reality, 64 ounces comes from a very old estimate of the total fluid intake the average person needs—from all sources (tea, coffee, soda, fruit, water, clam chowder, baked get the picture).

Obey Your Thirst

Thirst is a good indicator of how much each person needs to drink. Obey your thirst. Don't be afraid to drink water during an emergency. Indeed, you'll need to stay hydrated to stay healthy, but you don't need to force yourself to drink simply for the sake of drinking. Common sense suggests that you'll need the same amount of water during a disaster that you would need any other time. You will probably drink a little more, if only because you'll be more active in the aftermath of a disaster.

If you follow the official recommendations for storing water—a gallon per day per person—and drink what you need, you should have more than enough to get by.

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