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How much water is there on the Earth?

water.usgs.gov

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Re: How much water is there on the Earth?

#11

Post by jofer »

Retric wrote: post #5
exacube wrote: post #3

Can someone make a comment on the sustainability of our current water consumption, in terms of the US, other parts of the world, and the world itself? If we are not living sustainably, should we expect more investment across the world on things like desalination plants (I understand that desalination is really energy-expensive currently, but will that change by much?)

The best example is the Ogallala Aquifer. "At places, the water table was measured to drop more than five feet (1.5 m) per year at the time of maximum extraction." https://en.wikipedia.org/wiki/Ogallala_Aquifer So it's a huge resource of fresh water that's being drained much faster than it's replacement rate. But, building deeper wells is cheap and there is little value in untapped water so it's reasonable for now. H…

>In theory these Aquifers could be used as a cheap form of transport...

For what it's worth, an aquifer isn't an underground river... It's solid rock. What would you be transporting?

Re: How much water is there on the Earth?

#12

Post by cjensen »

logfromblammo wrote: post #8
cfontes wrote: post #2

Every time I see this it amazes me how little rivers represent of the whole fresh water available and how much Antarctica does.

But on the other hand, even if every non-floating glacier and snowpack melted and flowed into the ocean, that would only increase its mass by 2%. Combine that with the maximum thermal expansion from -4 C to 50 C, which would increase volume by 1.5% (and kill us all), and the highest the ocean could possibly rise above its current level is about 10m. The highest storm surge ever recorded was about 15m. The tsunami wav…

The math: (1) the linked article says there is 24e6 km3 of water in ice caps, glaciers, and permanent snow. (2) Area of Oceans from Wikipedia is 360e6 km2. (3) The statue of liberty is about 93m, (Base is 46m, Statue is 47m)

Division gives 0.066km of sea level rise if all of item #1 melts into the oceans, which is 66 meters. (In a more complex model, warmer atmosphere would adsorb some of it as increased absolute humidity.)

For the Statue of Liberty, that's enough to cover the entire base plus ~40% of the statue. The movie AI is wrong, but it's a lot closer to correct than the "10m" you quote.

Re: How much water is there on the Earth?

#13

Post by mturmon »

cjensen wrote: post #12
logfromblammo wrote: post #8

Earlier quoted context omitted.

But on the other hand, even if every non-floating glacier and snowpack melted and flowed into the ocean, that would only increase its mass by 2%. Combine that with the maximum thermal expansion from -4 C to 50 C, which would increase volume by 1.5% (and kill us all), and the highest the ocean could possibly rise above its current level is about 10m. The highest storm surge ever recorded was about 15m. The tsunami wav…

The math: (1) the linked article says there is 24e6 km3 of water in ice caps, glaciers, and permanent snow. (2) Area of Oceans from Wikipedia is 360e6 km2. (3) The statue of liberty is about 93m, (Base is 46m, Statue is 47m) Division gives 0.066km of sea level rise if all of item #1 melts into the oceans, which is 66 meters. (In a more complex model, warmer atmosphere would adsorb some of it as increased absolute hum…

In addition, the parent comment has omitted groundwater. Good current estimates for groundwater volume (in the OP, http://water.usgs.gov/edu/earthhowmuch.html) are very close to icecap volume (24e6 km^3).

And we are pumping this groundwater (~700 km3/yr as of 2000, and increasing [ * ]), which raises water levels and at the same time lowers land elevation as ground subsides. Depending on the Hollywood disaster scenario, that could play a role.

Atmospheric water, on the other hand, is a rounding error in this context.

[*]: See fig. 3 of http://onlinelibrary.wiley.com/doi/10.1029/2010GL044571/full

Re: How much water is there on the Earth?

#14

Post by mturmon »

exacube wrote: post #3

Can someone make a comment on the sustainability of our current water consumption, in terms of the US, other parts of the world, and the world itself? If we are not living sustainably, should we expect more investment across the world on things like desalination plants (I understand that desalination is really energy-expensive currently, but will that change by much?)

Groundwater is the resource we are depleting, because everything else runs in a circle. Here is a good worldwide groundwater study, based partly on gravity inversions from the GRACE twin satellites: http://www.jpl.nasa.gov/news/news.php?feature=4626

The conclusion is: Probably the most at-risk aquifer (based on people affected and severity) is in the Gangetic plain in northern India. There are also critically threatened aquifers in the Arabian peninsula, southeast China, and our own Sacramento Valley.

This conclusion is supported by other hydrological modeling groups as well (e.g., the very highly-cited, but older, http://onlinelibrary.wiley.com/doi/10.1029/2010GL044571/full)

Re: How much water is there on the Earth?

#15

Post by mturmon »

krauthammer wrote: post #9
Retric wrote: post #5

Earlier quoted context omitted.

The best example is the Ogallala Aquifer. "At places, the water table was measured to drop more than five feet (1.5 m) per year at the time of maximum extraction." https://en.wikipedia.org/wiki/Ogallala_Aquifer So it's a huge resource of fresh water that's being drained much faster than it's replacement rate. But, building deeper wells is cheap and there is little value in untapped water so it's reasonable for now. H…

People outside of Nebraska aren't going to get water from the Ogallala Aquifer. It's sacred. You should make other plans.

This is a weird comment, because of course the Ogallala Aquifer extends through eight states, and has been extensively tapped in all of them for decades.

Re: How much water is there on the Earth?

#16

Post by krauthammer »

mturmon wrote: post #15
krauthammer wrote: post #9

Earlier quoted context omitted.

People outside of Nebraska aren't going to get water from the Ogallala Aquifer. It's sacred. You should make other plans.

This is a weird comment, because of course the Ogallala Aquifer extends through eight states, and has been extensively tapped in all of them for decades.

Most of it is in Nebraska. The sentiment in the downvote is the same reason why I shared the comment. If you, as Californians, think you can just plan to take fresh water from Nebraska you're going to find yourselves mistaken.

Re: How much water is there on the Earth?

#17

Post by Retric »

jofer wrote: post #11
Retric wrote: post #5

Earlier quoted context omitted.

The best example is the Ogallala Aquifer. "At places, the water table was measured to drop more than five feet (1.5 m) per year at the time of maximum extraction." https://en.wikipedia.org/wiki/Ogallala_Aquifer So it's a huge resource of fresh water that's being drained much faster than it's replacement rate. But, building deeper wells is cheap and there is little value in untapped water so it's reasonable for now. H…

>In theory these Aquifers could be used as a cheap form of transport... For what it's worth, an aquifer isn't an underground river... It's solid rock. What would you be transporting?

Water, it's fine if it takes 10 years to move water from point A to point B as long as you don't need to build and maintain a pipe. Also, they are not solid rock or water, it's more like gravel with water in-between but the flow rate can get fairly high due to size even if the flow speed is very low. 1 mile per day is slow but * 365 days * 10 years that's a long way.

Re: How much water is there on the Earth?

#18

Post by logfromblammo »

cjensen wrote: post #12
logfromblammo wrote: post #8

Earlier quoted context omitted.

But on the other hand, even if every non-floating glacier and snowpack melted and flowed into the ocean, that would only increase its mass by 2%. Combine that with the maximum thermal expansion from -4 C to 50 C, which would increase volume by 1.5% (and kill us all), and the highest the ocean could possibly rise above its current level is about 10m. The highest storm surge ever recorded was about 15m. The tsunami wav…

The math: (1) the linked article says there is 24e6 km3 of water in ice caps, glaciers, and permanent snow. (2) Area of Oceans from Wikipedia is 360e6 km2. (3) The statue of liberty is about 93m, (Base is 46m, Statue is 47m) Division gives 0.066km of sea level rise if all of item #1 melts into the oceans, which is 66 meters. (In a more complex model, warmer atmosphere would adsorb some of it as increased absolute hum…

Rise in ocean level increases the surface area of the ocean, because most coastlines are not vertical cliffs. What is the average slope of dry land between 0m and 10m above sea level?

Reviewing the math, I concede that I may have been off by a factor of 4. But not 6.6!

The estimate for the amount of water needed to cover all land but the summit of Everest is easier, since the upper limit is an ellipsoidal shell 8848m thick. That's about 4.5x10^9 km^3, which is 3.4 times the current ocean volume. Then it's just a matter of estimating how much of that volume is already full of solid matter, and reducing the amount of water needed by the rock that is already there.

Re: How much water is there on the Earth?

#19

Post by [deleted] »

krauthammer wrote: post #16
mturmon wrote: post #15

Earlier quoted context omitted.

This is a weird comment, because of course the Ogallala Aquifer extends through eight states, and has been extensively tapped in all of them for decades.

Most of it is in Nebraska. The sentiment in the downvote is the same reason why I shared the comment. If you, as Californians, think you can just plan to take fresh water from Nebraska you're going to find yourselves mistaken.

[deleted]

Re: How much water is there on the Earth?

#20

Post by krauthammer »

krauthammer wrote: post #16
mturmon wrote: post #15

Earlier quoted context omitted.

This is a weird comment, because of course the Ogallala Aquifer extends through eight states, and has been extensively tapped in all of them for decades.

Most of it is in Nebraska. The sentiment in the downvote is the same reason why I shared the comment. If you, as Californians, think you can just plan to take fresh water from Nebraska you're going to find yourselves mistaken.

Keep downvoting me. You're still not getting the water.
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