Could pumping ocean water into desert areas help reduce sea level rise?

Question

I have been reading the discussion about pumping sea water into the desert for purposes of irrigation and changing the dry climate of that area, but what about to just purely offset the rising sea levels? Could pumping ocean water (with solar power) north of Malibu California into the dry areas help with coastline erosion and put water into the desert as a secondary but not primary benefit? I am a completely non-scientific person who just happens to have an interest in coastal erosion so I welcome all your educated thoughts on this. Ideally it would be done in all the deserts globally to have a coordinated effort. Think of the infrastructure jobs in places like Africa. It would require a “world bank” initiative to create the funds to do this but as a global coordinated effort it may be required as part of planet rehabilitation. Yes I said “create” the funds, ie “print money” which would have a slightly inflationary effect on world economies but would mostly “inflate” depressed economies through wealth redistribution since these economies would likely be the major supply of labor. Like we see in Canada when the people from poor fishing towns went to work on the pipelines and brought cash back home.

Answer 1

No, this is not practicable.

Imagine making another Lake Superior, the 3rd most voluminous lake on Earth, which according to Wikipedia holds 10% of the world's fresh surface water (excluding the ice in Antarctica). It has a volume of 12,100 km³, and would cover about one-fifth of California (at the same depth of about 150 m).

The ocean has an area of 361 million km², so removing another Lake Superior's worth of water would reduce its depth $d$ by:

$$\Delta d = \frac{12.1\times 10^3}{361 \times 10^6} = 33.5\times 10^{-6}\ \mathrm{km, or}\ 33.5\ \mathrm{mm} $$

... a bit over one inch. According to sealevelrise.org, this is about 10 years' worth of rise.

If you had 639 5400-horsepower Pentair Fairbanks Nijhuis pumps (the most powerful pump in the world, built for keeping the Netherlands dry), you could pump at 38 million litres per second and keep up with sea-level change (not accounting for evaporation or rainfall). At 4000 kW per pump, I think this would require the combined output from the six or seven largest solar farms in California, or a bit more than the output of the Diablo Canyon nuclear power plant.

Unfortunately, there are a lot of other factors controlling local sea-level; see this other answer for example. Not to mention the issue of figuring out where this saline lake will go...

Answer 2

Taking water out of the sea does require energy to lift it even if it's destination will eventually be below sea level. The dam idea of retaining rain water would require energy and resources for the production of the dam and require the loss of usable land. That is not the best dam way to approach this solution.

Removing water up stream, from say the Mississippi or Rio Grande, could be diverted to a lower elevation area via a pipeline or canal system. This too would require energy and resources to build, but the fresh water could at least be sent to areas that are currently unusable arid areas. This would result in a greening effect without the risk of contaminating water tables below. Another benifit would be the ability to increase the amount available farm land without the need of taking water from an already depleted ground water source. Also replenishment of water tables would occur, and your end goal of reducing the amount of water entering the ocean would be accomplished.

Answer 3

Yes, it could reduce sea level rise, but it would be no good for irrigation. Many deserts, like the Aral Sea and Death Valley, are below sea level. This means you would not need to use energy to pump the water, but could use the siphon principle. Some people say that even if you filled all these low-lying deserts with sea water, it would not do much to lower sea level. However, it would have many other beneficial effects, especially in the Aral Sea. It would greatly improve marine transport, create new fisheries, prevent the present salt desert being blown onto agricultural land, and quite likely change the climate so there would be more precipitation.

Another way to reduce sea level, though it would be only by a tiny amount, would be to build more dams. Deprived of the held-back rain water, the sea level would reduce a little if enough rainwater was prevented from reaching the sea. The dams would produce carbon neutral power, create fisheries and be used for irrigation. On the other hand, if the proposed dams on the Nile are anything to go by, they also have the potential to start wars unless they are sited with great care and good international diplomacy and cooperation.

Answer 4

It is my genuine opinion that YES

How much exactly?

See the example: https://en.wikipedia.org/wiki/Qattara_Depression_Project

The Qattara depression is a region that lies 60 m below sea level on average and is currently a vast, uninhabited desert. By connecting the region and the Mediterranean Sea with tunnels and/or canals, water could be let into the area. The inflowing water would then evaporate quickly because of the desert climate. This way a continuous flow of water could be created if inflow and evaporation were balanced out. With this continuously flowing water, hydroelectricity could be generated.

According to this answer: 3mm

(current annual sea rise is around 3-4mm per year)

According to my math: 3mm

Volume of Ocean 1,350,000,000   cubic kilometer
Volume of Qattara   1213    cubic kilometers
        
The ratio   0.0000008985185185  
Average depth of Ocean  3700    meters

0.0000008985185185 * 3700m = 0.003324518519m
        
0.3324518519cm
3.324518519mm

Evaporation, changing water table, changing weather patterns not included .
Too many 2nd and 3rd order effects to reliably predict.

Calculation above: pure math based on the volume.

Scientific papers about Quattara Depression Project

• Linked from the Wikipedia notes - Mapping of the Qattara Depression, Egypt, using SRTM Elevation Data for Possible Hydropower and Climate Change Macro-Projects

The transformation of Qattara Depression into isolated anthropogenic inland sea could provide some ocean level adjustment, as well as generate energy, induce rainfall over some of the adjacent desert, reduce hottest desert daytime and nighttime air temperatures, and permit new local-use fisheries (aquaculture) as well as international tourism resorts.

• https://energycentral.com/c/ec/qattara-depression-project-time-revisit - very detailed proposal, including building it in stages, as the water flows into the depression it generates hydropower

Despite nearly a century of studies and proposals, and despite high interest on the part of Egyptian authorities, all plans for development of the depression have come to naught. In the end, they foundered on the analysis of costs vs. benefits and risks. A lot has changed, though, in the four decades since the last feasibility study was commissioned — and ultimately rejected — by the Egyptian government of Anwar Sadat. Perhaps it’s time to revisit?

Technical feasibility and roadmap

This can be achieved with the technology that is available Today:

• developed in stages
• generating hydropower in the process
• pumping water uphill when excess energy

TBD. TBC. This answer can be improved. Old papers didn't account for Elon Musk and Boring Company though when calculating the cost.

Financing

ROI of reducing sea levels might be better than relocating cities that go underwater, however it will require some transnational agreements (country A has a sinking city, country B has a depression, financing coming from X).

Availability of labour

There is another large space project - The Grand Africa Green Up - they mentioned availability of labour. Useful to know.

Ethical aspect of geoengineering

We are already doing geoengineering with greenhouse gases in the atmosphere 🤷‍♀️ to use some desert and create energy, create jobs, and reduce sea levels - benefits far outweigh any potential concerns.

Note about glaciers and $$$

Geoengineer polar glaciers to slow sea-level rise

If nothing is done, 0.5–5% of the world’s population will be flooded each year after 2100. For example, a 0.5-metre rise in Guangzhou, China, would displace more than 1 million people; a 2-metre rise would affect more than 2 million1. Without coastal protection, the global cost of damages could reach US$50 trillion a year. Sea walls and flood defences cost tens of billions of dollars a year to construct and maintain.

Related projects

Not affiliated in any way, just being aware of their existence, in the theme of using desert (not just flooding):

• http://carbon.ycombinator.com/desert-flooding/ - it focuses on farming algae for CO2
• company that does exactly that: https://www.brilliantplanet.com/
• https://en.wikipedia.org/wiki/Desertec
• https://en.wikipedia.org/wiki/Medgrid
• https://xlinks.co/ - solar farm on Sahara, cable to the UK
• https://suncable.energy/ - solar farm in Australia, cable to Singapore

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EDIT / UPDATE: I've updated this answer a few times to reflect the feedback in the comments - thank you 😇 If you can, if you feel like it - please reverse the downvotes so that this answer receives some attention and bubbles on top - math adds up and people are already actively working on it.