Can Huge Man-Made Lakes Fix Our Rising Sea Levels?

Welcome to an important new Gawker feature, "Hey, Science," in which we will have our most provocative scientific questions answered by real live scientists (or related experts). Never let it be said that reading this blog is not the educational equivalent of sitting in a Ph.D.-level classroom, not paying attention. This week, experts answer the question: Can we fix the problem of rising sea levels by constructing massive man-made lakes on useless land?

THE QUESTION: Rising sea levels caused by global warming threaten the future of American civilization. Coastal cities, including many of our greatest metropli, could be inundated and destroyed. How to address this seemingly intractable problem? I (not a trained scientist, but a respected "free thinker") had a bright idea: What if we dug canals from the coastline and funneled water to massive, man-made inland lakes, which we located in relatively unpopulated areas? In this way we could relocate seawater away from where it threatened us most (the coast) and towards inland areas that we weren't using much anyhow, like Kansas. Sure, it would require a lot of effort and expense—but better to turn Kansas into a great lake than to see New York, Miami, and L.A. flooded, right?

Could this brilliant idea work? We turned to real live experts to find out. Hey, science!

Kevin Haas, Associate Professor of Environmental Fluid Mechanics and Water Resources, Georgia Tech:

You have an interesting idea for dealing with sea level rise. [Ed.: thank you, yes.] A couple of points that you would need to consider. Relative sea level rise, which is the change of the water level relative to land, is not just from the rising ocean but also can occur in places where the land is sinking. The New Orleans area is one such example. In other areas it is not a problem, where the land and sea are both rising so there is no relative change.

However, the rising seas is a global ocean issue from the release of the water from ice in the polar regions as well as an expansion of the water due to the temperature rise. So the volume of water that must be stored to make an impact is immense. To quantify it you should consider the total surface area of the oceans around the globe compared to the surface area of the land (around 3 to 1). So to reduce the sea level rise by only 1 ft, you would need 3 ft of water on all the earth's land. The most effective defense is probably to build on higher elevation and further inland.

Another issue is storm surge which occurs when storms push water ashore acting as a more regional effect. Although as Superstorm Sandy demonstrated, that region can be extremely large. Hence the volume of water associated with storm surge is also immense. Trying to divert the water to temporary storage would be extremely difficult because of the large required volumes. To date the most effective defenses have been some sort of barrier system which keeps the water out. The Netherlands have built such systems.

Matthew Huber, Director of the Purdue Climate Change Research Center and Professor of Earth, Atmospheric, and Planetary Sciences, Purdue:

I've thought about this kind of problem for several years now and I can say that some aspects of the idea are completely crazy and easily discounted, but other aspects are only slightly crazy and not easily discounted.

As a solution to sea level problems this is a completely crazy idea that should be discounted out of hand. Assuming the necessary canals could be built, one would need to connect the ocean to basins that were below sea level (other options require water flowing uphill, which is difficult). The total area (and volume) of dry land that is below sea level is rather small.

It is on the order of thousands of cubic kilometers, whereas the volume of the oceans is 1.3 billion cubic kilometers. If we call that 1 billion (1e9 km^3) and the total volume of land which is below sea level and dry 10,000 (1e4 km^3) (this is an overestimate) then you can begin to see the problem. The total amount of land to cover is about 1e5 of the ocean's volume, or .001%.

The surface area of the oceans is ~3.3e8 km^2 and if you imagine adding 1m of sea level evenly over that area you have a cube of .001km*3.3e8 km^2=3.3e5 km^3 of water, but the area we have to fill on land is at most 1e4km^3, so the ratio is 1/33 or 0.03. So maybe, at best, with a huge amount of effort we could do something about 3cm of sea level rise.

Then there's all the other problems: like putting salt water on an aquifer will guarantee a lack of useful water in a region for generations to come; the cost and difficulty of building all the canals and finding the required amount of space that isn't already used; the loading of the continents will locally depress the lithosphere there potentially raising relative sea level nearby and self-gravitation effects (adding mass onto the continents drags water toward the shoreline) will also raise relative sea level along the nearby coasts.

Generally it's a bad idea for sea level issues, but under the right circumstances there might still be uses for the general concept. [Ed.: thank you]

Phillip Roberts, Professor of Environmental Fluid Mechanics and Water Resources, Georgia Tech:

Hamilton, yes I'm afraid that the idea is wacky and completely impractical. Apart from the huge expense of such a project, the volume of the oceans is so (relatively) vast that it is not possible to build a lake large enough to have any significant effect. For example, if the Great Lakes were drained of freshwater and replaced with seawater, the ocean water level would drop by only about two inches!

Hermann Fritz, Associate Professor of Environmental Fluid Mechanics and Water Resources, Georgia Tech:

The idea is basically not new, but not to counter sea level rise. The relieve volumes involved are just not of relevance.

However there have been projects to turbine seawater into large desert depressions in Northern Egypt to generate power.

Hence it would be feasible to fill up desert depressions which are below sealevel and send in seawater which would however mostly evaporate again. Therefore mainly for power production. [Ed.: our idea has many potential benefits, you see.] Other such areas could be the Dead sea or the Desert Valley in the US.

Whether any of this makes economical sense is a different story.

John Dracup, Professor of Environmental Engineering, Berkeley:

Dear Hamilton, Do the Math. [Ed.: no.] The earth has a surface area of 510,100,000 km^2. The oceans are 70% of the earth's surface area. If the oceans rose 1 km, that would be a volume of water equal to 357,070,000 km^3. The surface area of the U.S. is 9,827,000 km^2. If you tried to store all of this sea level rise in the U.S., you would need a lake that covered the entire U.S. and had a depth of 36 km.

THE VERDICT: The idea is not practical, due to the sheer volume of water out there. But you have to salute the dynamic, creative mind that came up with it.

[Thanks to all of the experts who lent us their expertise. Do you have a provocative question, idea, or theory for "Hey, Science?" Email me. Image by Jim Cooke.]