Removing 1% of Earth's Water

[alxian]

To support billions of humans on Mars, water will be required. There may not be enough Ice on mars for so much water to be removed to support so many people.

 

We know that Earth's less than 1% of fresh water supports at least 7 billion humans in relative comfort. ignoring that the other 99% supports the bulk of life on earth from which we fish..

 

If 1% of the ocean could be desalinated and transported to mars, what would that do to Earth? in terms of weather and our water cycle?

[Jay-qu]

I dont know about effects on earth, but that is a hell-of-a-lot of water! The volumes of earths oceans is 1.37 × 10^9 km^3, one percent of that is 1.37x10^7 km^3 or 1.37 x 10^19 Litres, which is the same in kilograms..

 

I dont think you could possibly move that much water..

[Zythryn]

Ignoring that it would be far easier to capture a comet and seed Mars with it, I would guess you would lower the sea level about... 10-20ft?

Not sure what that would do to weather patterns.

I would guess it would lower the capacity of the oceans to act as a heat sink and CO2 sink although I am not sure about that as the surface area would be close to the same.

[Boerseun]

I don't think it'll ever be very practical to do, but as a hypothetical exercise, I don't actually think much would happen. It would lower sea-levels some, and that's about it, I guess. I don't think it'll seriously screw with the weather patterns or the hydro cycle, either. Weather is more determined by the surface area of the oceans than the volume of the oceans. It has also been demonstrated that water lying on the seafloor (+-2-3kms deep) cycles to the surface around once every thousand years. So the deep water don't really contribute anything on the short term to our weather patterns. If you take 1% away from that, I don't even think you'll notice anything at all.

[Qfwfq]

Try lowering the surface level by about 20 feet and see how much the shorelines change. Some basins such as the Adriatic and the Red Sea would change quite a bit. I think however 20 ft is an underestimate.

 

So the deep water don't really contribute anything on the short term to our weather patterns. If you take 1% away from that, I don't even think you'll notice anything at all.

How do you choose to remove the deep water and not that at the surface? :ebomb:

[alxian]

trully, even if you were doing deep water hydrothermal power generation the water from the deep depths wouldn't be that far because the pipes wouldn't go down that far.

 

but yeah i can see that being as good a place as any to take the water from. besides our own polar ice caps.

 

if any desalinization occurs then getting that water to orbit and taking it to mars would still require quite a bit of energy. as for capturing a comet.. that water may not be any cleaner than the salty water from earth, plus if you had a ship capable of getting to mars fast enough to haul water, i don't think the source really matters.

 

lowering the earth sea level by 20 feet sounds dangerous. where some regions depend on hydroelectric power their potential water source may be weakened.

[Boerseun]

How do you choose to remove the deep water and not that at the surface? :surprise:

Simple. You don't. Remove 1% of all the seawater, and you'll still end up with deep water and shallow water. And the deep water will still take 1000 years to circulate to the surface. The point was just to illustrate how slow circulation in seawater is.

 

Thought it was pretty clear, though.

[Boerseun]

...where some regions depend on hydroelectric power their potential water source may be weakened.

Au contraire! Seeing as hydroelectric schemes work on the principal of converting potential energy to electricity through the water falling from a higher level to a lower level, and the ultimate lowest level would be sea level, it follows that the further the sea recedes and the lowest level drops, the more energy can be tapped from any conceivable hydroelectric sheme. The screwup for hydro schemes would be if rainfall in the catchment area drops, not the sea receding.

[Zythryn]

I think the changed seacoast would have some affect on drainage patterns. Not sure how this would affect the rivers and weather local to the coasts.

 

The 20ft guess was pulled out of thin air. I suspect it would be more but I like to err on the side of not exaggerating.

[Qfwfq]

With less ocean surface, you would be somewhat altering the rain cycle, whereas I don't see the problem as being the circulation between deep and shallow water.

 

Uhm, Alxain, I don't see why the pipes wouldn't reach that deep, my point was that there isn't any substantial distinction in where you take it from. Ask Archimedes.

[ronthepon]

Perhaps we could try and make a somewhat accurate prediction on how much the drop will be. I think I'll have to see how deep the seas are in average.

[pgrmdave]

Well, are there any estimates as to how much water there is on earth? Then at least we could find how much volume would be lost.

[Qfwfq]

There certainly are, likely you can find them.

[ronthepon]

Well, I've been working on this, and here's what I've found.

 

I began with this site for data.

 

http://www.enchantedlearning.com/subjects/ocean/

 

From this site, I'm thinking about the average depth to be =

 

64186(15215)+33420(12881)+28350(13002)+7848(14000)+5106(3953)/(64186+33420+28350+7848+5106)

 

Note that I've multiplied the areas of the oceans with their av. depths and added them. I've then divided it with the total area.

 

=1905735728/138,910

 

=13,719.2119 feet

This average vaule of the depth seems quite fine to me.

 

=0.3048(13719.2119) meters

 

=4,181.61579 meters (I love SI units)

 

 

Total volume of sea water = 1,338,000,000 km3 (-wiki)

 

= 1.338 * 10^9 Km3

 

= 1.338 * 10^18 m3 :kiss: Is this 'kay?

 

Assuming that the reducton in depth is large compared to reduction in any other dimensions, upon reduction in volume of sea water,

 

V = hA

 

A = V/h

 

Giving A = 1.338*10^18/4.181*10^3

 

A = 3.2 × 10^14 (This is different from surface area)

 

dV = dh A

 

dh = dV / A

 

Since dV is around one percent,

 

dh = 0.01V/A

 

dh = 1.338*10^16/3.2*10^14

 

dh = 41.8

 

41.8 meters! :surprise:

 

This value is too huge. Definitely more tham 20 feet. Will somebody having some free time bother to check my calculations? forty meters seems... kinda crazy.

[Qfwfq]

Not all that crazy at all. I think the Adriatic and the Red sea would get quite empty and many other surfaces would emerge, many islands near coasts would be connected etc... Of course this means the exact calculation isn't really linear, but then the question was 1% of all water, not just marine, so that tends to increase the effect.

[pgrmdave]

Well, here are the sites I was able to dig up.

The volume of earth's lakes:

http://hypertextbook.com/facts/2005/HamidaDaud.shtml

About 120,000km^3

 

The volume of earth's oceans:

http://hypertextbook.com/facts/2001/SyedQadri.shtml

http://www.newton.dep.anl.gov/askasci/env99/env241.htm

About 1.33 billion km^3

 

http://ga.water.usgs.gov/edu/earthwherewater.html

- a site that may be potentially useful, has a lot of water statistics.

[Boerseun]

I still don't think it'll make that much of a difference. Sure, land bridges might reappear, like the one between England and Europe. But think about it - the water can only really recede up to the continental shelves. From there on, it'll be mostly a vertical drop. So you can in effect take much more than 1% of the water away before you really start screwing around with surface areas. Our coastlines on average aint very far away from the shelves, at the most a few hundred kilometers. 41 meters for 1% don't sound excessive at all, but keep in mind the shelves are on average about 300-400 meters deep. So you won't even reach the edge of the shelf.

 

The worst bit will be that you'll kill off every coral reef known to man.

 

But then, the speed at which even the most aggressive pumping of water will proceed at, will give the coral population more than enough time to migrate downwards. Volcanos sink faster than you'll be able to lower the sea level, and the corals seem just dandy with that.

 

So that won't be a problem, either!

 

You can, of course, start by emptying all the freshwater lakes. But they will simply refill again from rainwater originating from oceanic evaporation, which won't differ much from what it used to be due to the surface areas remaining pretty much the same. And the lakes' levels depends on local topography. So they'll fill right back up to where they were, lowering sea levels even if you pump exclusively from freshwater lakes. You might pump from aquifers, but the same thing will happen. The aquifer will simply refill to where it was as dictated by local topography, taking water out of the hydro cycle, eventually lowering sea levels as a consequence. I can't see how you'd take water out of the system without finally lowering sea levels. But seeing as it won't make a serious impact on land area vs. sea surface area, nothing much would change, I guess. Okay - rivers at sea level like in deltas and such will start to cut aggressively into the riverbeds due to the accellerated flow, and this cutting will continue until they reach ea level again. But this will happen at such a glacial pace (as with the coral reefs) that nobody'll notice.

 

Figure out a way to remove 1% of the water overnight, and yes, then you'll have some serious problems.

 

So, the scale of the problem only depends on the size of your pump! :Alien: