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Earth Has Less Water Than You Think

by Jason Major on May 8, 2012

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All the water on Earth would fit into a sphere 860 miles (1,385 km) wide. (Jack Cook/WHOI/USGS)

If you were to take all of the water on Earth — all of the fresh water, sea water, ground water, water vapor and water inside our bodies — take all of it and somehow collect it into a single, giant sphere of liquid, how big do you think it would be?

According to the U. S. Geological Survey, it would make a ball 860 miles (1,385 km) in diameter, about as wide edge-to-edge as the distance between Salt Lake City to Topeka, Kansas. That’s it. Take all the water on Earth and you’d have a blue sphere less than a third the size of the Moon.

Feeling a little thirsty?

And this takes into consideration all the Earth’s water… even the stuff humans can’t drink or directly access, like salt water, water vapor in the atmosphere and the water locked up in the ice caps. In fact, if you were to take into consideration only the fresh water on Earth (which is 2.5% of the total) you’d get a much smaller sphere… less than 100 miles (160 km) across.

Even though we think of reservoirs, lakes and rivers when we picture Earth’s fresh water supply, in reality most of it is beneath the surface — up to 2 million cubic miles (8.4 million cubic km) of Earth’s available fresh water is underground. But the vast majority of it — over 7 million cubic miles (29.2 cubic km) is in the ice sheets that cover Antarctica and Greenland.

Of course, the illustration above (made by Jack Cook at the Woods Hole Oceanographic Institution) belies the real size and mass of such a sphere of pure liquid water. The total amount of water contained within would still be quite impressive — over 332.5 million cubic miles (1,386 cubic km)! (A single cubic mile of water equals 1.1 trillion gallons.) Still, people tend to be surprised at the size of such a hypothetical sphere compared with our planet as a whole, especially when they’ve become used to the description of Earth as a “watery world”.

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Makes one a little less apt to take it for granted.

Read more on the USGS site here, and check out some facts on reducing your water usage here.

Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.
– from The Rime of the Ancient Mariner, Samuel Taylor Coleridge
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About

A graphic designer living in Providence, RI, Jason writes about astronomy and space exploration on his blog Lights In The Dark, Discovery News and here on Universe Today.

Tagged as: Earth, globe, how much water, USGS, water

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  • Le_REAL_MACK

    That is still a f^ckton of water any way you cut it. Imagine standing in Topeka and looking up from the ground at that thing.

  • Kawarthajon

    That’s a pretty tall ball of water – much taller than Hubble orbits and about 1/10 the diameter of the earth. Also consider that the Eart’h's crust, where most of the water lives, is very thin, no more than 70km deep.

  • Nephish777

    What about water in magma and lava?

    • http://twitter.com/JPMajor Jason Major

      All the water.

      • http://pulse.yahoo.com/_WPNZVY3EW6RGXU2JWS5LGGFWFY Checkers Crossfox

        Actually, it appears this only takes into account water in-and-above the crust; water present in the mantle wasn’t accounted for (and I’m not sure we even have a reliable estimate of the water content of the mantle).

        • http://www.selectioneffect.info/ Corrie Engelbrecht

          Considering that the Earth’s mantle consists of liquid magma and pressurised solid rock, I think we can conclude that this estimate includes all the water.

  • http://outerhoard.wordpress.com/ Adrian Morgan

    For non-Americans, here are some more analogies to show how far 1,385 km is (the diameter of the ball). For Australians: Distance from Melbourne to Brisbane. For Europeans: Distance from Paris to Warsaw. For astronomers: The size of Sedna.

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  • Gadi Eidelheit

    Wow! this is on I am going to translate…. Very interesting

  • JM

    Nothing like a reality check.

    Wonder how large a sphere needs to be to hold the denser part of the atmosphere…say up to 10,000 feet?

    • Albion Bowers

      JM,
      I thought almost the exact same question this morning. So computing the size of a ball of atmosphere (all of it, at sea level pressure and density) comes out to 2087.86 km diam (1296.56 mi). That’s only nominally larger than the size of the ball of water…
      Al

  • briansheen

    In one way it is not surprising, water only covers 2/3rds of the Earth’s surface to a fairly shallow depth. (when compared to the diameter of our planet. ) It is a great reality check though.
    Roseland Observatory. UK.

  • maurizio52

    What a huge amount of water!
    Only freshwater is about 300giga litre procapite considering 7 billions people living on the earth.
    Each human being could swim in a giant freshwater’s droplet 80m in diam. (260 feet) , can you imagine it?
    Considering all of the water, the droplet’s diameter should rise to about 270m (900 feet).
    It is enough freshwater to fill a personal square swimming pool 100m wide (330feet) and 30m (100 feet) deep.
    I feel… wet, not thirsty at all… ;-)

    • http://profile.yahoo.com/GQPEXA4CF55RNRIIVWKKN4NI64 rama

      Whether we feel thirsty or wet, better to conserve our water resources NOW!!

      • Olaf2

        Water resources are going no where, all you need to do it is purify it again.

  • Prism2Spectrum

    And all that life-sustaining water is said to have been naturally out-gassed, and/or deposited by hail-storm of cometary impacts.

    However old the Earth actually is, that amazing aquamarine sphere has apparently been preserved through all Earth’s living history, in the finest balance with the vast continental landmasses, and through all erosive processes and material transfers of time, from lands to seas, in dynamic change of ages.

    Though ocean levels have apparently been raised and lowered (or continental shelf regions themselves), from warm/cold climatic episodes (Ice Sheets/melt-offs), the breaking waves of endless shores, define the edges of its bulk to narrow tidal zones, ebbing and flowing only so far. Little changed over a span of life. In scales of landmass depths and ocean volumes, that is remarkable. As Earth’s desolate Moon of fortuitous placement, works its silvery “magic” over our air-vaulted “Blue Planet”.

    Yes, indeed, “Water, water, every where”, a wonder of our world so fair.

  • http://www.facebook.com/people/Fons-Jena/100002853847514 Fons Jena

    And that amount is becoming smaller and smaller isn’t it? Rockets using liquid oxygen and hydrogen dump tons of water into space or does the exhaust fall back to earth? Correct me if I’m wrong.

    When I think about the fact that we are launching one rocket after the other the only thing I can think about is that we are discarding tons of precious metals and liquids/gases that we will never be able to recycle. It hurts.

    • Murray Bell

      Dude, stop being such a pansy! You’re at the extreme end of the greeny spectrum, take a look outside every now and then it’s not all doom and gloom. In the grand scheme of things, what’s some fuel and metal in the name of science when you consider all the asteroids / meteoroids that come through the atmosphere everyday?! Seriously, it’s depressing that you’re so concerned about this.

      • squidgeny

        If it helps, consider all the rockets to be an investment in future space-mining. There’s water on the moon dontcha know!

    • http://pulse.yahoo.com/_TWAGTCDI3FU6XN2PQC2UVMH64Y Daddy Bud

      they are developing a machine satalite that will go up and bring down obsolete sats from orbit..a space Junk vaccuum if you will…spend a drop get a drop back…sort of an endless cycle.

    • Alanator

      Who`s to say we won`t get hit by an asteroid next week, which replenishes all the water, but you can`t enjoy it for another 50 million years! (:

  • http://www.facebook.com/sail4evr Joe Cazana

    It is that big a volume only because water does not compress. Imagine all of earth’s atmosphere…stuff all of it into a large tank

    • RemyVTR15

      Space Balls much?

    • http://pulse.yahoo.com/_TWAGTCDI3FU6XN2PQC2UVMH64Y Daddy Bud

      Atmosphere is very thin and is included in this measurement…as is ice and all other forms of water…its foolish to worry as its going to be the one thing that will limt the humans on this rock…after we kill off the other animals for their water

  • http://twitter.com/JMaytum Julian Maytum

    “Makes one a little less apt to take it for granted.” – We’re talking humans here right? One of the reasons I want space exploration and colonization to go full speed ahead is *because* of my fellow humans. Very interesting article though :)

  • http://www.facebook.com/joeshuster Joseph Shuster Sr

    I wonder if that incorporates atmospheric water, soil water, ice, and moisture in rock. It would be cool to see a pie chart of salt, fresh, and the others.

  • RemyVTR15

    Ok I’m going to be a bit snarky here. Soooo I guess the answer is to flush twice with the low flush toilets… Perhaps the better answer is to harvest glaciers and icebergs.

    This really comes down to population control doesn’t it? So… we then gotta figure out who gets the short stick… because I reckon the Libs won’t just volunteer to self-sacrifice… I mean just look at the big AGW champions… Those ‘conservatives’ of the Earth.

    Water is precious. I conserve what I can and have actively tried to use greywater on plants… But I’m a realist also. The 3rd world is not going to limit their promise at development and better lives just because we say so.

    Water will become more expensive and will become a resource that wars are fought over. I predicted this in the 70′s in a story about Virginia-NC fighting over Kerr Lake and other water resources. They’ve long had battles about shared water… California and the West have long fought over the Colorado.

    It’ll only get more exciting with time.

    Maurizo52 has a great point, it’s a bunch of water per person… but that is all the person gets for their entire life…and then they have to pass it down to the next generation…which will necessitate splitting it in atleast half. 5 billion in the 70′s I think and now 7 billion 30 years later??? 10 billion perhaps in 15 years? My ‘droplet’ is shrinking, no matter WHAT I do….
    D@mn…. I am a RWC and sound like a Greenie. But math doesn’t lie.

    ohhh wait, it doesn’t matter. It still goes back into the tank called Earth to be reused like always!

  • Adrianmc5

    Than “you” think?…I knew this. I ain’t stupid!

  • lcrowell

    The Earth has a modest amount of water. A few of these extra-solar planets that have been found have water up to hundreds of kilometers in depth.

    LC

    • http://pulse.yahoo.com/_TWAGTCDI3FU6XN2PQC2UVMH64Y Daddy Bud

      Water or Liquid….there is a significant difference

  • Howard Dutton

    What’s with the fresh water “100 miles across”? Seems like 50 miles radius would be 50^3 * 4/3 * Pi = about 1/2 million cubic miles… article then goes on to to say it’s 9+ million cubic miles. Perhaps it’s 200 miles across?

  • Sean Leslie

    Hey Jason, I think you’re missing a few zeroes in a couple of places.

    Paragraph 5:
    “But the vast majority of it — over 7 million cubic miles (29.2 cubic km) is in the ice sheets that cover Antarctica and Greenland.”

    And paragraph 6, sentence 2:
    “The total amount of water contained within would still be quite impressive — over 332.5 million cubic miles (1,386 cubic km)! (A single cubic mile of water equals 1.1 trillion gallons.) ”

    Shouldn’t they be 29.2 million and 1,386 million respectively?

  • http://www.facebook.com/people/James-Jestes/721040172 James Jestes

    I never would have guessed it to be that thin. Water on this planet is much scarcer then we were led to believe as kids

  • ITSRUF

    All the water on Earth could fit on the head of a pin if it was in a black hole.

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