# Fresh Water: Great Lakes and ?

**URL:** <https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582>\
**Category:** Factual Questions\
**Created:** [July 15, 2003, 4:48am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582 "2003-07-15T04:48:29Z")\
**Posts on this page:** 13\
**Page:** 1

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**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\
**Post date:** [July 15, 2003, 4:48am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/1 "2003-07-15T04:48:29Z")

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They claim the Great Lakes makes up 20% of the world’s fresh water supply. Is there another sole (or chain of resources) that make up another significant portion? I WAG the Caspian Sea, which is supposedly the world’s largest lake (not really a sea) with Lake Superior coming in 2nd? Maybe some fishermen know?

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**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\
**Post date:** [July 15, 2003, 4:56am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/2 "2003-07-15T04:56:07Z")

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Lake Superior is a Great Lake.

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**Author:** ![Cillasi](https://avatars.discourse-cdn.com/v4/letter/c/71e660/32.png) [@Cillasi](https://boards.straightdope.com/u/Cillasi)\
**Post date:** [July 15, 2003, 5:03am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/3 "2003-07-15T05:03:44Z")

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Most of the Earth’s fresh water supply is tied up in glaciers, ice sheets (Antarctica) and the ice cap (Arctic). In sheer volume (7 1/4 million cubic miles), Antarctica takes the record at about 70% of the world’s fresh water supply and contains 90% of the world’s ice.

[http://hypertextbook.com/facts/2000/HannaBerenblit.shtml](http://hypertextbook.com/facts/2000/HannaBerenblit.shtml)

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**Author:** ![matt\_mcl](https://avatars.discourse-cdn.com/v4/letter/m/7ab992/32.png) [@matt\_mcl](https://boards.straightdope.com/u/matt_mcl)\
**Post date:** [July 15, 2003, 5:03am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/4 "2003-07-15T05:03:55Z")

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No, no, no. _Canada_ supposedly contains 20% of the world’s fresh water, of which 9% is supposedly in usable form.

Isn’t the Caspian Sea salty?

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**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\
**Post date:** [July 15, 2003, 5:06am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/5 "2003-07-15T05:06:52Z")

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Lake Baikal, in Russia (Siberia) contains nearly a quarter of all the world’s fresh water. The Caspian Sea is not very deep, on average, but still contains, according to one source ([greeninformation.com](http://greeninformation.com)) 44% of the world’s lake waters (I don’t know how it stacks up as a percentage of fresh water). It is not entirely fresh water, as it has a salt gradient.

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**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\
**Post date:** [July 15, 2003, 5:09am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/6 "2003-07-15T05:09:42Z")

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[Comparison of world’s major lakes in Google cached file](http://216.239.53.104/search?q=cache:KZZOzyZYEMYJ:igpl.home.attbi.com/Lakes.html+lake+superior+salinity&hl=en&ie=UTF-8)

Note that Superior also has less volume than Baikal or Tanganyika (due to their greater depths) although it has much greater surface area.

Note also, however, that the Caspian has 11% salinity while the others tend to have no measurable salinity, so when you are talking about “fresh” water, the Caspian has a problem. To use that water for crops or drinking, _some_ effort must be made to remove salt, (although the Caspian has only 1/3 the salinity of the oceans).

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**Author:** ![netscape\_6](https://avatars.discourse-cdn.com/v4/letter/n/8c91f0/32.png) [@netscape\_6](https://boards.straightdope.com/u/netscape_6)\
**Post date:** [July 15, 2003, 7:03am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/7 "2003-07-15T07:03:34Z")

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is it low enough you could drink water out of only the caspian and not die of thirst?

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**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\
**Post date:** [July 15, 2003, 11:00am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/8 "2003-07-15T11:00:20Z")

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> [@](#):
>
> \*Originally posted by netscape 6 \*  
> \*\*is it low enough you could drink water out of only the caspian and not die of thirst? \*\*

NO.  
The average salinity of the oceans is [about 3.5%](http://geosun1.sjsu.edu/~dreed/105/exped7/5.html), and that is not considered very drinkable.

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**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\
**Post date:** [July 15, 2003, 11:16am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/9 "2003-07-15T11:16:02Z")

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There is a very interresting website, run by the **International Lake Environment Committee**. They have a database, with lots of data on most lakes: [here](http://www.ilec.or.jp/database/database.html).

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**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\
**Post date:** [July 15, 2003, 11:24am UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/10 "2003-07-15T11:24:45Z")

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I think maybe Tom missed a decimal point and meant to say the Caspian’s water is 1.1% salt. Drinking that may not be exactly healthy, but it takes more like 2% to kill you by dehydration.

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**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\
**Post date:** [July 15, 2003, 12:46pm UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/11 "2003-07-15T12:46:40Z")

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> [@](#):
>
> \*Originally posted by Grey \*  
> \*\*Lake Superior is a Great Lake. \*\*

I realize this, but I think you missed the second statement which may not have been clearly expressed. The point was that the Caspian Sea is the largest lake, not actually a sea…of which Lake Superior ranks 2nd largest lake. Sorry for any confusion… - Jinx

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**Author:** ![Yossarian](https://avatars.discourse-cdn.com/v4/letter/y/9de0a6/32.png) [@Yossarian](https://boards.straightdope.com/u/Yossarian)\
**Post date:** [July 15, 2003, 1:13pm UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/12 "2003-07-15T13:13:05Z")

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“Fresh” water is defined as water having \<1000 mg/L total dissolved solids (TDS; this is the Texas Water Development Board definition [[link]](http://oceanworld.tamu.edu/geos105/WaterQuality.pdf), but all are similar).

The Caspian Sea has TDS ranging between 13500 and 16000 mg/L, which is firmly in the “very saline to brine” range. (Cite: [http://www.desline.com/articoli/5101.pdf](http://www.desline.com/articoli/5101.pdf)). In the Caspian Sea, like all other lakes that form in a closed basin (Great Salt Lake, Dead Sea, etc.), the only way for water to leave the basin is via evaporation, which results in the high TDS characteristic of these lakes that makes them “salty”.

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**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\
**Post date:** [July 15, 2003, 1:27pm UTC](https://boards.straightdope.com/t/fresh-water-great-lakes-and/188582/13 "2003-07-15T13:27:59Z")

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I’m not sure what the difference is between “salt” and “salinity,” but the site to which I linked gave the Caspian “salinity” as 11% and another site to which I did not link claimed that it was 1/3 as salty as the oceans. (I also have no idea whether the site to which I linked is correct, of course.)

I suspect that TDS, as noted by **Pantellerite** , or any measure of parts per million or parts per liter or whatever is a better measure than some ill-defined percentage, in any event.