# Would it be geographically feasible to store water on land to counteract sea level rise?

Based on a misunderstanding of another post, I prepared an estimate of how much water would be required to lower sea level by one meter. the main question would be: could this be stored on land?

• First of all, there hasn't been true global warming in 13 years, so you're really talking about a non-problem here. Recent decreases in northern ice sheets have been more than made up for by southern ice sheets, and at this point the northern ice sheets are actually growing again. Second - seriously? Where are you going to put that, specifically? Considering that the planet is 2/3 water, if you sacrificed 1/10 of the land on the planet, you'd have to dig a hole 30" deep to reduce sea levels by 1" So you just bulldozed Asia and bankrupted every government on the planet. – user1154134 Dec 11 '14 at 19:49
• @user1154134 do you have references to support these claims? remember, we are a question and answer site, not a discussion forum. – user889 Dec 11 '14 at 20:27
• Is your question whether manual re-glaciation is a physical possibility? I hesitate to post my answer pointing out that it's currently not economically viable to do much of anything on a planetary scale. – Mazura Dec 12 '14 at 1:15
• Storing water on land will also cause the land to sink/lower under the weight of the water. – user2338816 Dec 12 '14 at 1:31
• Not feasible on land as evaporation will redistribute it again. Your only hope is deep aquifers which btw also have more capacity than surface. – stali Dec 22 '14 at 17:04

Using the eTopo1 data Eakins and Sharman has calculated a hypsographic curve for the earth. In the elevation span between + 6 to -6 m they found that land area will change by 396 000 km2 per meter sea level change. In the range -7 to -51 m below current sea level the land area will change by 251 000 km2 per meter sea level. Thus to get an area the size of Zimbabwe (391 000 km2) or Norway (385 000 km2) (data from the World bank) sea level will currently have to be lowered by 1 m. Since the ocean surface is about 360 000 000 km2 (e.g. The Physics factbook) this would mean a total of about 360 000 km3 of water which in turn is comparable to the Caspian Sea (371 000 km3 according to a Wikipedia compilation)

So where does that lead? Clearly adding a Caspian Sea somewhere on land is not an easy task so the question is how much land need to be gained and where? Remember that all coasts are not the same, topographically.

As a side point, the Greenland ice sheet contains enough water to raise sea level by about 7 m. Hence the ongoing warming is a far more problematic issue when it comes to sea level change and counteracting this volume would be 7 times more challenging than the calculation made above. That is a sobering perspective.

Reference

Eakins, B.W. and G.F. Sharman. Hypsographic Curve of Earth's Surface from ETOPO1, NOAA National Geophysical Data Center, Boulder, CO, 2012

• Great calculations! Given that even if the heating trend were to slow, the latent effects in water and ice would continue for some time. Admittedly, the volume is smaller than I thought it would be - desalinating it and storing it in a series of large dams could be a solution to the fresh-water problems a lot of places have - but that is thinking way out of the box on my part. – user889 Dec 11 '14 at 20:29

The largest desalination plant is the sun - with its action on the oceans and turning sea water into fresh water (by evaporation->clouds->rain) it has more capacity than any man made structure to pump ocean water. To "store" rain water would require the damming of a significant body of water - but you would have to tolerate a significant rise in the water level over that smaller region (Or if you can freeze the water, a very large pile of ice like Greenland).

For example if you built a 150 m tall dam at Gibraltar and kept all the water from the major rivers that supply it locked up, the rise in the sea you would need is over 140 m (2.5 million square kilometers vs 3600 million square kilometers for all oceans). Unfortunately the rate of evaporation of the Mediterranean is greater then the net flux of all the rivers supplying it so that would not work unless you covered the entire thing with a reflective plastic sheet to prevent evaporation. You would kill all the flora and fauna in the sea, and all tourism, too.

We need another plan to save the earth.

• Please explain how does the sun reduce the amount of dissolved solids in sea water. – Gimelist Dec 22 '14 at 7:10
• @Michael the sun makes rain - and that is the water with "reduced dissolved solids". Giant distillery/pump. You just have to find a way to stop the rain from getting back to the sea. – Floris Dec 22 '14 at 14:22
• Then edit your answer to make it clear. From your answer it seems as if the sun somehow magically desalinates ocean water. – Gimelist Dec 22 '14 at 14:44
• @Michael see if my edit clarifies my intention? – Floris Dec 22 '14 at 14:46

The best solution to this type of problem would be to desalinate all excess water at shorelines. This could be done with desalination plants that use their own energy produced from tidal/wave generators. There are plenty of empty reservoirs in the world that would be happy to take any excess water that is desalinated. I'm assuming if we can build transcontinental pipelines for oil.. we can do it for water.

Pump the water somewhere it will freeze and remain so. Who's buying?

My question would be if it's economically viable. If we can put man on the moon and send probes outside our solar system I see no reason why we can't perform the basic task of freezing water and putting it back where it belongs where we want it. Only at the precipice do we change. When rising sea levels begin to threaten all human life on Earth we might just do something about it.

Geographically it would be difficult to make a reservoir large enough that didn't just leak back into the water table. Mining a cistern into faultless, living granite might be a toss up as to the energy/money required compared to just pumping that water to a permafrost area; manual re-glaciation (\$).

Anything reasonable is feasible; how many zeros in your check book? That silly end-of-the-Earth movie where they go to the core and save the world comes to mind. One trillion dollars? Will you take a check?

• This answer almost seems discussion-forum-ish, however, you make valid points about the reservoir required, so +1 – user889 Dec 13 '14 at 2:26
• yes would have been a pretty short answer. – Mazura Dec 13 '14 at 2:33
• Yes, that would be true, but I can see how the ideas in the other paragraphs link as well. – user889 Dec 13 '14 at 2:49