# How much water is there on earth, per human? **URL:** \ **Category:** Factual Questions\ **Created:** [June 18, 2022, 6:17pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433 "2022-06-18T18:17:15Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![StarvingButStrong](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/starvingbutstrong/32/335_2.png) [@StarvingButStrong](https://boards.straightdope.com/u/StarvingButStrong)\ **Post date:** [June 18, 2022, 6:17pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/1 "2022-06-18T18:17:15Z")
Thinking about all the stories about the current droughts, and how climate change is disrupting everything and how likely it is to lead to mass migrations and water wars and all… Suppose we decided to be really “fair” and parcel the Earth’s supply of water out evenly to every human being. Ignore that water is constantly in motion, being reused and recycling around – we just take the total amount that exists at one moment. We’ll also ignore that there are a zillion animals and plants that might be considered to have some claim on water. (Hey, ‘screw them’ seems to be our reaction to non-human species rights in general, right?) For ‘practical’ reasons, let’s give each human three ‘containers,’ one each for fresh water, salt water, and ice. What I really want to know is, how big would those containers be? Use any measurement system that seems appropriate. Would we each get a swimming pool’s worth of fresh water? 15 oil tankers full of salt water? A cube of ice 60 meters per side? Hmmm. Do we need another container for the moisture in the atmosphere? Or maybe we condense that somehow and add it to the freshwater tank. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 18, 2022, 6:56pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/2 "2022-06-18T18:56:10Z")
> **[Water distribution on Earth](https://en.wikipedia.org/wiki/Water_distribution_on_Earth)** > > Most water in Earth's atmosphere and on its crust comes from saline seawater, while fresh water accounts for nearly 1% of the total. The vast bulk of the water on Earth is saline or salt water, with an average salinity of 35‰ (or 3.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land. In all, water from oceans and marginal seas, saline groundwater and water from saline closed lakes amount to ... Using the figures from the Wikipedia page, and assuming a population of 8 billion, I get the following volumes per person: 1.7 x 10^8 m^3 salt water 3.0 x 10^6 m^3 ice & snow 1.3 x 10^6 m^3 fresh water 530 supertankers of salt water (67,000 Olympic swimming pools) 10 supertankers of ice & snow (1,200 Olympic swimming pools) 4 supertankers of fresh water (520 Olympic swimming pools) ---
**Author:** ![Ponderoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponderoid/32/19221_2.png) [@Ponderoid](https://boards.straightdope.com/u/Ponderoid)\ **Post date:** [June 18, 2022, 6:56pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/3 "2022-06-18T18:56:49Z")
I don’t know the numerical answer, but your question reminded me of this visualization on how much water there is on Earth: [![](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/all-the-worlds-water.jpg) ](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/all-the-worlds-water.jpg) ---
**Author:** ![StarvingButStrong](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/starvingbutstrong/32/335_2.png) [@StarvingButStrong](https://boards.straightdope.com/u/StarvingButStrong)\ **Post date:** [June 18, 2022, 11:12pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/4 "2022-06-18T23:12:45Z")
> [@Riemann](#): > > 530 supertankers of salt water (67,000 Olympic swimming pools) > 10 supertankers of ice & snow (1,200 Olympic swimming pools) > 4 supertankers of fresh water (520 Olympic swimming pools) Wow. My no-real thought estimates were off by a factor of !500! on the fresh water, hey, but “only” about 35 on the salt water. Thanks for tackling the math end! > [@](#): > > Ponderoid > > I don’t know the numerical answer, but your question reminded me of this visualization on how much water there is on Earth: That is a stunning image! It’s all in which way you’re looking, isn’t it? I was stunned at how LARGE the answers were numerically, and seconds later stunned at how small the answer is when comparing to the planet. It looks like, proportionately, the Earth has just about the same amount of water as a bowling ball that had been dipped in a bucket of water and pulled right out! ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 18, 2022, 11:54pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/5 "2022-06-18T23:54:21Z")
> [@Riemann](#): > > 4 supertankers of fresh water (520 Olympic swimming pools) It is worth noting that the fresh water is not evenly distributed. About [20% (give or take) is in the five Great Lakes](https://www.epa.gov/greatlakes/facts-and-figures-about-great-lakes) and another [20% (or so) is in Lake Baikal in Russia.](https://wwf.panda.org/discover/knowledge_hub/where_we_work/lake_baikal/) ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 19, 2022, 12:14am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/6 "2022-06-19T00:14:34Z")
> [@Whack-a-Mole](#): > > About [20% (give or take) is in the five Great Lakes](https://www.epa.gov/greatlakes/facts-and-figures-about-great-lakes) and another [20% (or so) is in Lake Baikal in Russia.](https://wwf.panda.org/discover/knowledge_hub/where_we_work/lake_baikal/) But you are giving percentages of the _surface_ fresh water, which in total is only about 1% of the fresh groundwater. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 19, 2022, 1:37am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/7 "2022-06-19T01:37:19Z")
And this is how much people there is: > **[World Population Meatball](https://knowyourmeme.com/memes/world-population-meatball)** > > The World Population Meatball, also known as the Sphere of Human Goo or the Forbidden Meatball, is a photoshopped illustration that originated on Reddit in August 2021, depicting an image of a 7.88 billion-person meatball placed in New York's Central... ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 19, 2022, 3:04am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/8 "2022-06-19T03:04:48Z")
> [@Darren\_Garrison](#): > > And this is how much people there is: > > [World Population Meatball | Know Your Meme](https://knowyourmeme.com/memes/world-population-meatball) Average person 62kg gives a sphere of radius 1km. I think that’s about the width of Central Park, right? There are about 1500 supertankers of people goo. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 19, 2022, 3:20am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/9 "2022-06-19T03:20:35Z")
We seem to be using up that groundwater awful fast. Is your 99% of water being underground account for usage? Does it mean it is accessible? > Researchers found that 30 percent of the Kansas portion of the Ogallala Aquifer has already been pumped out, and another 39 percent will get used up in the next half-century at existing rates. Kansas, clearly, is on the fast track to depletion. As a result, agriculture production is likely to peak around 2040 and decline after that. [SOURCE](https://www.washingtonpost.com/news/wonk/wp/2013/09/12/how-long-before-the-midwest-runs-out-of-water/) ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 19, 2022, 4:31am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/10 "2022-06-19T04:31:22Z")
> [@Whack-a-Mole](#): > > Does it mean it is accessible? OP didn’t ask for “accessible” water. I used estimates for the total amount of water that exists, broken down in that Wikipedia page. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 19, 2022, 4:44am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/11 "2022-06-19T04:44:20Z")
> [@Riemann](#): > > OP didn’t ask for “accessible” water. Yeah they did… > [@StarvingButStrong](#): > > Suppose we decided to be really “fair” and parcel the Earth’s supply of water out evenly to every human being. You cannot parcel out what is not accessible. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 19, 2022, 4:50am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/12 "2022-06-19T04:50:40Z")
You conveniently ignored the title of the thread > How much water is there on earth and > we just take **the total amount that exists** at one moment If OP was concerned only with accessible fresh water, he wouldn’t be asking about the content of the oceans or the ice caps. In any event, all the figures are all in the Wikipedia article. If you want to break out the accessible fresh water, go for it. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 19, 2022, 6:37am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/13 "2022-06-19T06:37:39Z")
There is also the mantle, which either has lots of water or lots less water. [https://www.earthmagazine.org/article/thirsty-mantle-subduction-zones-swallow-more-water-thought/](https://www.earthmagazine.org/article/thirsty-mantle-subduction-zones-swallow-more-water-thought/) > **[Subduction May Recycle Less Water Than Thought - Eos](https://eos.org/research-spotlights/subduction-may-recycle-less-water-than-thought)** > > A new analysis of seismic data from the Middle America Trench suggests that previous calculations have vastly overestimated the total amount of water transported to the mantle worldwide. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 19, 2022, 10:20am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/14 "2022-06-19T10:20:45Z")
It would seem the OP was not clear. Do they want a measure of all the water that is possible to squeeze out of the earth or a measure of all the water that each human could reasonably have access to? An H2O molecule in the mantle, while part of the earth, is of little use to a human on the surface (and [it seems there is a helluva lot of water there](https://ssec.si.edu/stemvisions-blog/there-ocean-below-your-feet) which may be a great deal of your 99% but we will never access it). Personally, I think both data points are interesting. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 19, 2022, 1:28pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/15 "2022-06-19T13:28:02Z")
> [@Whack-a-Mole](#): > > An H2O molecule in the mantle To be clear, the figures I gave above for the total amount of fresh water only included fresh groundwater, which exceeds the amount of surface water by about 100-fold. Although not immediately accessible, I believe this entire volume is all in dynamic contact with the surface. Total groundwater may fit some broader definition of “accessible”. These figures did not include water that may be trapped much lower in the mantle. I think this is more speculative, there are no precise estimates for this. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [June 19, 2022, 3:57pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/16 "2022-06-19T15:57:26Z")
You beat me to that Ponderoid. It’s a great graphic by USGS. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [June 19, 2022, 6:53pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/17 "2022-06-19T18:53:14Z")
I had read somewhere that far from the ocean deeps, if the earth were the size of a billiard ball, it would have a barely discernable film of moisture on it. That illo drives the point home. ---
**Author:** ![Oooklout](https://avatars.discourse-cdn.com/v4/letter/o/ba8739/32.png) [@Oooklout](https://boards.straightdope.com/u/Oooklout)\ **Post date:** [April 26, 2023, 8:17am UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/18 "2023-04-26T08:17:28Z")
Significantly, about 1/60th of the oceans’ volume is piled up on Antarctica. That’s OK except that ice doesn’t like to pile up, The pressure liquifies the lowest layers so that it skates off downhill. So far, the 300ft thick bank of sea ice floes has slowed up the collapse but now the sea is warming, the sea ice is disappearing and the glaciers are noticeably accelerating. Antarctica iis also about 1/60th of the world’s surface area, so 60m of ice loss gives 1m of ocean rise. (use yards or fathoms if you like, same wet feet). Ice is 1000s of metres (yards) thick on Antartctica, for the monent anyway. ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [April 26, 2023, 3:52pm UTC](https://boards.straightdope.com/t/how-much-water-is-there-on-earth-per-human/966433/19 "2023-04-26T15:52:30Z")
> [@Whack-a-Mole](#): > > Does it mean it is accessible? Fresh water doesn’t have to be surface for it to be accessible.