VOICES Voices Icon Ideas and Insight From Explorers


Walking Water: H20 and the Human Body

Photo: Woman drinking bottled water at the beach
The human body is dependent on water. Photo: Mark A. Vargas, Flickr Creative Commons


Fourteen gallons of water.

That’s how much water I’m walking around with in my body mass.  Imagine carrying 120 pounds of water –that’s three nearly full 5-gallon water jugs — around with you all day long, every day of the year.

No wonder I’m so tired at the end of the day.

You can do this math for yourself.  An average adult’s body is 60-70% water; for children it’s closer to 75% but it can get as low as 45% if you’re overweight.

Take your body weight and multiply it by the appropriate percentage of water and you’ll see how many pounds of water you’re packing.  If you want to convert those pounds of water into gallons, just divide by 8.4.

Add another 24 pounds of skin and what you’ve basically got is hundreds of thousands of years of human evolution producing an ambulatory water balloon wrapped in flesh.

University of Chicago scientist Neil Shubin writes in his book Inner Fish that we hiccup because of a design malfunction in our nervous system and a breathing apparatus passed down from fish and tadpoles.  It appears that when our animal ancestors crawled out of the ocean they somehow forgot to purge their water ballast as well.

Fortunately, we also have a three-pound brain that can tell our body balloon where to go.  How to fall in love.  How to launch fellow balloons into space.

Before your brilliant cerebral cortex starts thinking that dehydrating yourself would be a smart diet plan, I’ll caution you that our highly evolved body balloons run on a very thin tolerance for water loss.

During a normal day, we breathe, pee, and sweat out about three quarts of water, amounting to 5-10% of our body’s water. Note that if you’re running the 150-mile Marathon Des Sables across the Saharan Desert in Morocco, you’re likely leaking more than 12 quarts a day.  If you’re not continuously replenishing your body’s water you can run into trouble in a hurry.

With a deficit of as little as one quart you’re likely going to start losing some cognitive function, alertness, and ability to concentrate.  If you lose a gallon you’ll start feeling pretty lethargic, and you’ll likely have a bad headache.  If you’re down two gallons you’re going to be sick enough to be in the hospital.  Three gallons and you’re in the morgue.

Yet our water needs are so much greater than simply keeping our bodies hydrated, and therein lies the great water challenge of the 21st century.  We use water to grow our food, generate our electricity, and manufacture our clothes.  If you visit National Geographic’s Water Footprint Calculator you’ll see that it takes about 2,000 gallons of water per person each day to support an American lifestyle.  That places a lot of strain on the freshwater systems of our planet, a theme that I’ll return to repeatedly in the coming weeks and months in my Water Currents blogs.

Water is at the very core of our being.  John Muir once said, “The rivers flow not past, but through us.”

How right he was.


  1. […] human body is made up of approximately 70% water.  During an average day of basic activity, we lose 5-10% […]

  2. […] human body is made up of approximately 70% water.  During an average day of basic activity, we lose 5-10% […]

  3. […] human body is made up of approximately 70% water.  During an average day of basic activity, we lose 5-10% […]

  4. […] About 71% of the Earth’s surface is covered by water. Similarly, a human body is made of up to 75% of water (when we are children). Water is everywhere and is essential for any kind of life on this planet. (Source: USGS and National Geographic) […]

  5. […] Since our bodies are composed of 60% to 70% water, it is easy to see why we need to drink more water. On the clean eating plan, water is the recommended beverage. The goal is to get four or five 12-ounce glasses of water per day. […]

  6. […] itself deep into your bones. You start to see yourself as a sack of cells and nerve impulses; ~75 percent water; a walking colony of bacteria; the 666th cousin thrice removed of the […]

  7. Water People! – TIMEHOOPER
    January 26, 12:40 pm

    […] According to National Geographic, losing just one quart of water results in lost cognitive function. High sugar-based and carbonated drinks do not hydrate as they deplete water to process. […]

  8. […] is essential to your body, especially because your body is made up of about 60-70% water. Water is constantly being circulated throughout your body, which is why it’s important to […]

  9. Welcome To Rayoonline
    July 15, 2016, 9:04 am

    […] But we also need to make sure that we stay fully hydrated. Our bodies are made up of anywhere from 60% to 70% of water, which is a key component of parts of our blood, organs, and even our […]

  10. GOOD ON THE DANCEFLOOR blog Re-spun13
    June 18, 2013, 10:30 pm

    Good day! I simply would like to give you a huge thumbs up for the great information you have got right here on this post. I’ll be coming back to your site for more soon.

  11. Willy Pereira
    Wichita Ks
    April 14, 2013, 6:07 pm

    Lets conserve and distribute well our earthly human
    water do not pollute or alter the living and non animated
    Molecular Biology
    Restruct our infrastructure and create jobs in blue, white
    and for other multicultural colorful habitats
    This will improve our economy.
    Thanks for sharing your informed view.

  12. Phil dunham | Myworldgreen
    April 22, 2012, 6:44 pm

    […] Walking Water: H20 and the Human Body – News Watch […]

  13. […] https://newswatch.nationalgeographic.com/2012/03/06/human-body-water/ Share this:FacebookTwitterLike this:LikeBe the first to like this post. This entry was posted in Uncategorized and tagged drinking water, Gallon, John Muir, Nature Conservancy, Neil Shubin, Rainsoft Ottawa, United States, University of Chicago, University of Virginia, water, Water footprint. Bookmark the permalink. ← FRIDAY THOUGHTS ABOUT OUR “TRUE FRIENDS” […]

  14. Brian Richter
    Crozet, VA
    March 14, 2012, 1:59 pm

    Hi Phil,

    You’re absolutely correct — I should have said “divide” rather than multiply! Thanks for catching this — a corrected version of the blog should be posted soon.

  15. Phil Dunham
    March 9, 2012, 4:53 pm

    Is it really multiply? I would have thought divide by 8.4.

  16. Phil Dunham
    New Jersey
    March 9, 2012, 4:49 pm

    Shouldn’t we divide the pounds of water by 8.4? I believe 8.4 gallons would weigh much more than a pound. I always thought a gallon weighed 8 pounds.