If so, could a massive reservoir offset sea level rises due to global warming?
Where could the largest reservoir be created and how big would it be?
I think it would be mind bogglingly huge.
To offset, say, a 1 cm sea level increase from the entire 361 million square kilometer surface area, you’re talking a volume of 1 cm * 361x10^6 km^2 = 3610 km^3
That’s a bit more than the entire volume of lake huron (cite) . So if you’re willing to scoop out something that size, just to offset a centimeter of rise, I suppose you could do it… I think it would be easier to build new inland cities to house all of the coastal population.
To answer you first question, no. The effect would be infintesimally small.
Let’s do some sums.
Total land area of Earth is about 150 million sq km.
Total area of the oceans is about 350 million square km, and the volume is 1,400 million cubic km.
So let’s say you managed to cover a whopping 10% of the Earth’s land area with 100 metres of water, somehow kept away from draining back into the sea.
You’ve reduced the total volume in the oceans by about (0.1 x 0.1 x 150,000,000) = 1.5 million cubic km. Out of a total of about 1,400 million cubic km. That equates to a drop of a little over 4 metres in the global sea level, or about 14 feet.
And that’s from covering one tenth of the whole of the land with 300 feet of water.
On a related note, someone on another forum I read once seriously suggested that everyone in the world ought to be given a load of containers to fill with water and store, to “keep it out of the oceans” and thus reduce sea levels. I did the sums and worked out that if everyone on earth stored 100 litres, we might lower the sea level by a couple of millimetres or so… I can’t be bothered to repeat the calcs so it might not even be that much!
Freshwater lakes obviously do hold water out of the world’s oceans, thus influencing sea level.
But my back-of-the envelope calculations suggested that the volume of all the freshwater lakes in the world (seems to be a bit over 100,000 km[sup]3[/sup]) would be sufficient to alter the level of the world’s oceans by about 30 cm.
So the OP’s scheme looks a tad impractical.
But maybe if we all had pools put in…?
To answer the second question, there are such things as natural basins from which water doesn’t flow to the ocean; the technical term for this is an endorheic basin. So maybe we could fill, I don’t know, Nevada with water in order to lower the oceans. It’d probably still be a pretty small contribution relative to the entire ocean, though.
Even if you could build enough lakes to offset much of the increase in water levels, there are going to be a lot of extinctions as many critters die due to the increased salinity.
How so? Even reducing the global sea level by, say, 50 metres (which would more than offset even the grimmest predictions of sea level rise for the next few hundred years) would only reduce the total volume of the oceans by a little over 1%. (The average ocean depth, globally, is around 4km.)
Such a tiny decrease in volume would surely have virtually no effect on salinity in the oceans.
What about Antarctica? Nobody lives there, and if the southern ice cap does melt, the ecology there is pretty much fucked anyway.
Isn’t this an idea doomed to fail anyway because of evaporation? And wouldn’t the reservoirs become increasingly saline thereby?
That said, I wonder how absorbent some areas might be? What if we were to make huge desalination plants and pump fresh(ish) water to the Sahara? Or desert areas in th US?
The OP has been answered – but let me address an assumption that seems to be behind it, because it’s a common misconception –
The rise in sea levels is almost certainly NOT the most important effect of global warming. There are some places, like Bangladesh and perhaps southern Florida, where this will be an expensive and devestating factor. But that’s nothing compared to the regional shifts in climatic things like temperature and, especially, rainfall – THOSE are the things will will cause large disturbances to the agriculture and ecology of entire countries, and THAT’s what will set in motion all kinds of social and economic problems (according to many scientists).
Not as easy to visualize as rising sea levels, but more important all around.
flood the Quattara Depression (N. Africa),the Dead Sea Basin (Israel), and the Slaton Se Basins? WE could take the edge off rising sealevels, and generate quite a bit of power in doing so. What happened to the idea, to run a canal from the Mediterranean Sea to the Dead Sea? Imagine all those millions of gallons-falling a mile! Lots of energy there!
On a sort of related note, rising sea levels = more water surface = more evaporation = more rainfall, right?
I can see how this might lead to more storms, and more intense storms, but how could it lead to extreme “desertification”? Wouldn’t the desert areas do pretty well with more rainfall?
Well, perhaps a quarter of a mile (link). Of course, once you open the floodgates on that mega-billion dollar canal, the basin starts filling up, so the drop - and the power generated - soon decrease. In the end, you’ve destroyed the homes of many people, trashed millions of acres, and are looking for your next project.