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Sahara Lake, the Solution for Sea Level Rise?

Column door Koen van Niekerk.

It has been some time since the world met Donald Trump and some of us are even getting used to his ‘particular’ way of thinking and saying what he thinks. And now that he is mister president of the United States of America we can begin to imagine the consequences that might have, for example on the topic of climate change and his impact on the landscape.

What caught my eye specifically is the impact that Trump looks like having on the landscape. He would like to build a wall over the south border with Mexico to whatever reasons he has for that. The physical and aesthetical impact that the (in)famous wall would have on the landscape and towns around that border is almost beyond imagination. But what might be more imaginable is the consequence of mister Trump’s presidency on climate. As we have heard in the campaigns throughout 2016, Trump is convinced that climate change doesn’t exist or isn’t mankind’s fault. It’s especially not America’s fault and so it is none of his responsibility. But while the world becomes indoctrinated by Trump, there are people that don’t believe in his ‘post-truth facts’ (I like the Oxford dictionary’s word of the year 2016) whatever meaning the word ‘fact’ has after months of campaigning.

There are people who see the rising sea level as the biggest threat by climate change, which makes sense if you live close to a sea. When I recently scrolled through my local newspaper, a man, we’ll call him Mr. X, wrote his solution to this problem in a letter to the editor (Jong, 2017). He explained the idea that the world can fix the consequences of the rising sea level by digging a hole in the surface of the earth to accommodate all that water. That seems like an idea because the Dutch do something similarly for centuries now. The Dutch dig series of canals which lead the water away from their land to pump it to the sea via a lake or a river to keep their land dry. I’m fascinated by this idea so let’s continue!

In my opinion, this lake should meet two requirements: 1) is it possible, can sea level rise be solved by this and how does this work in landscape? And 2) Is mankind able to make a large enough basin for all the water and, where would it be located? Mr. X thought of the calculations and location and came to the following:

  • The amount of water and ice on the world does not change

  • The surface of the Sahara desert is 9.400.000 km2

  • The average surface of the Northern icecap is 12.000.000 km2

  • The average thickness of this icecap is 2 meters

  • The average volume of the icecap is 0.002 x 12.000.000 = 24.000 km3

  • If 20% of the Sahara is dug out 20 meters deep, the depth this hole would be: 0.20 x 9.400.000 x 0.002 = 37.600 km3 = 37.600.000 m3

  • The biggest dirt moving equipment in the world, built by Krupp, has a capacity of 56.000 m3 per day

  • The number of workdays that the dirt moving equipment of Krupp has to run: 37.600.000 / 56.000 = 672 days

Mr. X’s conclusion: If the Northern icecap totally melts, the Sahara lake could take the water easily. An additional benefit of this lake is that, if a desalination plant is placed at the entrance and there is a supply of fresh water, the potential agricultural land around the lake is enormous! What is left, and Mr. X makes no statement about that, is the huge pile of sand remains. To strengthen dikes, or to build an artificial mountain? An interesting job for a landscape architect!

Unfortunately, the sea level rise is not solved this easily. Sea level works a bit more complex than this. When the icecaps melt there is more water and the volume of water gets bigger as the temperature rises. But, as Bert Vermeersen, researcher at the TU Delft, explains in the same paper about a month later (Hof, 2017), there is not ‘one’ sea level since the seas are not flat. If you travel from Australia to India by boat, you sail through a 100 meter valley in the sea, created by warmer and colder currents and the moon. Plus, he mentions, the weight of all that water pushes the surface of the earth down which influences land subsidence. Especially for the Netherlands, the water pushes the bottom of the North sea down and pulls the Netherlands with it.

So there we are, a simple solution for a very complex problem does not seem to work out very well, but maybe it gives us a starting point? The landscape architects of tomorrow could use the variety in sea levels to their advantage, inventing continental or regional solutions instead of one global solution. Maybe we can save the Netherlands from drowning by diverting water from the North sea to somewhere else? The landscape architects of tomorrow probably have the solution within reach, but for now, we can suffice with a letter to the editor in a local Dutch newspaper!

References Hof, G. v. (2017, januari 24). IJskappen smelten en zeespiegel... daalt juist! Brabants Dagblad, p. 11. Jong, C. d. (2017, januari 3). Noordpool smelt? Graaf een kuil in de Sahara. Brabants Dagblad, p. 11.

mei 16, 2017

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