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Are the Qattara Depression project and similar proposals too small in impact or more expensive than building better flood management, or why aren't we doing tho

Are the Qattara Depression project and similar proposals too small in impact or more expensive than building better flood management, or why aren't we doing those?

thombat 4y ago
Much too small. Using Wikipedia's figures: volume of Qattara Depression = 1,213 cubic kilometres, volume of Greenland ice sheet = 2,850,000 cubic kilometres. And the project is only useful as a long-term power source if the contents evaporate leaving space for renewed inflow, i.e. it only sequesters a fraction of its volume.
BurningFrog 4y ago
Making Qattara a bay of the Mediterranean would be great as a way to bring life and human habitation to the desert. It's incredibly expensive though. Scott Alexander estimated it would "reverse one year worth of global-warming induced sea-level rise" here: https://slatestarcodex.com/2016/04/15/links-416-they-cant-link-our-dick/ https://slatestarcodex.com/2016/04/15/links-416-they-cant-li...
- hinkley 4y ago
  There are 360 million square kilometers of ocean. Of course sea level rise increases the surface area a bit but if you assume 1 mm (1 millionth of a kilometer) goes straight up then each mm of sealevel is 360 cubic kilometers of water. We are depleting our aquifers at a rate of about 280 km^3 per year. US is down over 1000 km^3 since ~1900. I'm not sure how much of that ends up in the ocean, but reducing that number and taking it negative would go a long way toward slowing sea level rise.
  - BurningFrog 4y ago
    The comment above says filling Qattara takes 1,213 cubic kilometres, which would mean about 3mm lower sea level. Which would be a real change, but also quite small in the bigger picture. I guess depleting aquifers can lower land levels in those areas. I hear Jakarta has sunk 4 meters from that effect. But it's a separate thing from rising sea levels.
    - hinkley 4y ago
      I was thinking more of the fact that if it’s not below ground it’s above ground, so most of that water has been evaporated and deposited into the ocean.

Are the Qattara Depression project and similar proposals too small in impact or more expensive than building better flood management, or why aren't we doing those?

thombat 4y ago

Much too small. Using Wikipedia's figures: volume of Qattara Depression = 1,213 cubic kilometres, volume of Greenland ice sheet = 2,850,000 cubic kilometres. And the project is only useful as a long-term power source if the contents evaporate leaving space for renewed inflow, i.e. it only sequesters a fraction of its volume.

BurningFrog 4y ago

Making Qattara a bay of the Mediterranean would be great as a way to bring life and human habitation to the desert. It's incredibly expensive though. Scott Alexander estimated it would "reverse one year worth of global-warming induced sea-level rise" here: https://slatestarcodex.com/2016/04/15/links-416-they-cant-link-our-dick/ https://slatestarcodex.com/2016/04/15/links-416-they-cant-li...

hinkley 4y ago
There are 360 million square kilometers of ocean. Of course sea level rise increases the surface area a bit but if you assume 1 mm (1 millionth of a kilometer) goes straight up then each mm of sealevel is 360 cubic kilometers of water. We are depleting our aquifers at a rate of about 280 km^3 per year. US is down over 1000 km^3 since ~1900. I'm not sure how much of that ends up in the ocean, but reducing that number and taking it negative would go a long way toward slowing sea level rise.
- BurningFrog 4y ago
  The comment above says filling Qattara takes 1,213 cubic kilometres, which would mean about 3mm lower sea level. Which would be a real change, but also quite small in the bigger picture. I guess depleting aquifers can lower land levels in those areas. I hear Jakarta has sunk 4 meters from that effect. But it's a separate thing from rising sea levels.
  - hinkley 4y ago
    I was thinking more of the fact that if it’s not below ground it’s above ground, so most of that water has been evaporated and deposited into the ocean.