Wednesday, December 29, 2010

Water really is a scarce resource . . .

The US Geological Survey has published an astonishing image, showing all the water on the Earth - including fresh and salt water, glaciers, even the liquid in our own bodies - gathered into a sphere, and shown relative to the size of our planet.

Click here to see the original (much larger) version, plus more information about the quantity of water involved.

It certainly makes it clear how little water we have to play with on this otherwise barren planet, doesn't it?



Noons said...

All of Earth's fresh water, not all of Earth's water.

Shrimp said...

No, Noons, it says that is all of the water, including the oceans.

The representation is supposed to show a sphere about 860 miles in diameter, next to the Earth, a sphere approximately 7,900 miles in diameter.

bruce said...

The size of a sphere of land above sea level would be much smaller still.
Somehow all the worlds oceans seem like a lot more than we need.

Anonymous said...

Does that include all of the water vapor in the atmosphere?
In NE Florida, we get torrential rains in summertime (4+inches/hr).

Jenny said...

well it's not like we're really getting *rid* of it. At worst we just muck it up and have to clean it back up. But it's not it's being *destroyed*.

... IIRC, we lose some fraction annually to off-gassing from the atmosphere and get about the same back in from comets and such, yes?

Vonster said...

This is pretty speculative. They have to assume the amount of water underground which they simply don't know how much there is which could very well be more than what it above. Interesting, but hardly absolute fact.

Ritchie said...

As the rocky planets go, it's really quite a bit. Water keeps the plate tectonics going, and without that, we'd be done for.

Noons said...

The original author - Igor Shiklomanov - wrote about the fresh water in the planet. The original book is called "A guide to the world's fresh water resources". It's in the legend of the photo in the link.
The link is to a news article from USGS who didn't even bother to read the original title properly.
I repeat: this is a representation of the calculated fresh water in the globe. Not all water.

Shrimp said...

No, it isn't, at least not according to Igor Shiklomanov's own numbers.

Assuming that not everyone has a copy of the book, and so we're all on the same page, so to speak, I found the relevant table here, about a third of the way down the page:

As you can see, Shiklomanov's numbers clearly show the amount of water in total, and the amount of the water that is fresh water, expressed as a percentage of the whole.

Taking his total number of water, including the oceans, we have a volume of 332,600,000 cubic miles.

The sphere in the picture is about 860 miles in diameter. Volume of a sphere is 4 * PI * Radius cubed / 3

4 * 3.14159 * 430 cubed / 3 = 333,027,260.5733333

Slightly off, but remember that the original number of 860 is itself an approximation.

Going in reverse, we can take the 332,600,000 and multiply it by 3, divide by 4 and PI to get a number of 79,402,468.176942248988 etc etc.

The cube root of that number is approximately 429.8, giving us a radius of approximately 430 miles, or a diameter of about 860 miles.

The picture is a representation of all the estimated water on earth, including the oceans.

Shrimp said...

Not to belabor the point, but to put it this into a hopefully better and more graphic point, let's imagine the Earth as a ball with a smooth surface, with no valleys, mountains or surface features of any kind. For sake of argument, well say the Earth's average diamter is 7913.04 miles. This is taken from the Earth's actual diameters, measured in miles at the poles (7899.80), and the equater (7926.28), then averaged together to create a uniform diameter.

If we took the entire volume of water as estimated by Shiklomanov, including groundwater (which by definition is under the surface of the earth), and calculated the volume of the Earth-ball, then added the volume of the two together, the new larger diameter equals 7916.40, a difference in diameter of 3.36 miles. The radius (half the diameter) of the two combined is 3958.20 miles vs. the radius of the Earth-ball by itself is 3956.52 miles, a difference of 1.68 miles.

Placed upon the surface of said Earth-ball with the average diameter of 7913.04, it would completely cover the Earth-ball to a depth of 1.68 miles.

This fun factoid brought to you by somebody with waaaaaayyy too much time on his hands.

Anonymous said...

It's information from a federal agency, and now all of them are agenda-driven. Why believe any of it? Mosquitos can't carry HIV, margerine is good for you, just do what airplane hijackers tell you to do, FDA approved drugs are safe. Wait and see what kind of licensing, taxes (more!)controls and rationing on water are around the corner.