Flooding below sea-level: Siphonics Natural Engineering (c)

[Ken Caldeira]

Folks,

I ran across this pdf recommending the benefits of flooding sub sea-level desert areas.

I believe the author of this document (cc'd) would enjoy your comments.

Best,

Ken


___________________________________________________
Ken Caldeira

Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA

kcal...@ciw.edu; kcal...@stanford.edu
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
+1 650 704 7212; fax: +1 650 462 5968  

[Andrew Lockley]

It seems pretty counter-intuitive to me.

Firstly, flooding deserts to create either lakes or vegetation would generally reduce albedo (darken), leading to more solar energy being absorbed, and hence causing temperatures to rise.

Secondly, water vapour is a powerful greenhouse gas, and thus increasing its concentration in the atmosphere will cause further net forcing.

Thirdly, desert areas predominantly exist in areas of downwelling air.  Therefore, the creation of large cloud systems with high albedo over these regions would be unlikely.  This is in contrast to tropical forests, which create large clouds through evapotranspiration into rising air.

It seems that this approach would not have any immediate climate benefits.  It may, however, be a good way to cultivate deserts - although I suspect the maintenance costs, constructions costs and ever-present salinity problem would make it unattractive.  Look at the Aral sea region as an example of the difficulties in cultivating in brackish water.

A

2009/6/7 Ken Caldeira <kcal...@dge.stanford.edu>

[Sam Carana]

Since 1938, John Bradfield has called for rivers in Australia to be
turned inland, to create a permanently-filled Lake Eyre. Proposals to
pipe or channel seawater into Lake Eyre from the Upper Spencer Gulf
date back a long time; one such proposal was seriously considered by
South Australian Parliament in 1883. Lake Eyre is a usually dry lake
which at its lowest point is 15 meter below sea-level. The idea was
that flooding Lake Eyre would create clouds and rain for inland
Australia. The resulting vegetation would retain moisture and help
turn further desert and arid land into fertile soil.

Such hydraulic engineering schemes are part of the history of
geoengineering. Unfortunately, the Wikipedia page on hydraulic
geoengineering has been deleted.

Solar power (solar concentrators, vortex towers, etc) in the desert
could power such projects, i.e. pumping water over barriers, powering
earth-moving vehicles, etc, possibly complemented by desalination, CO2
air capture, spraying water into the sky, and more.

From the perspective of global warming, such projects will have a
number of effects, each constituting either positive or negative
forcing in terms of global warming. Water vapor acts as a greenhouse
gas, trapping heat - clouds, on the other hand, have a higher albedo
than deserts, so clouds will also reflect more sunlight back into
space. Vegetation has a lower albedo than desert - vegetation, on the
other hand, also draws CO2 from the air and stores it in the soil. I
believe that the overall impact will be beneficial, but I'd love to
see anyone come up with more calculations to support this.

Until now, such projects have been regarded as too expensive, i.e. if
the sole purpose was to create fertile land. However, the benefits in
terms of climate change may change that picture.

Cheers!
Sam Carana

[Bonnelle Denis]

Hello,

 

Some desert areas, notably near the southern Mediterranean coast, are indeed below sea-level. Letting sea water flow towards them is a rather old idea which has various rationales: triggering economical development, producing hydroelectric renewable energy, etc. Increasing water evaporation for geoengineering purposes is a new one. I'd like to emphasize a fourth one: producing very large quantities of renewable energy thanks to salt gradients.

 

This is because these sub-sea-level areas have already been flooded, in geological times, so that salt has accumulated there (they're called evaporites - others are located in the Danakil desert, also below sea-level, in eastern Eritrea and Ethiopia). As the reverse of sea water desalination, letting very concentrated brine (which can be produced by salt dissolution into sea water) and usually concentrated sea water melt with each other can produce renewable energy. See: http://en.wikipedia.org/wiki/Blue_energy

 

One technology (pressure retarded osmosis) is being developed by Norwegian society Statkraft:

http://www.statkraft.com/Images/Statkraft%20Osmotic%20Power_tcm4-5362.pdf. It uses the same osmosis membranes that are currently used for water desalination, however, for price competitiveness, further cost reductions should come from scale economies.

 

The other technology (reverse electro dialysis) is developed by Dutch Redstack: http://www.redstack.nl/RS-Pres01/RS-pres_bestanden/frame.htm

 

Both are mainly developed in order to yield the salinity gradient between fresh water and sea water, but, as they also notice, the gradient between seawater and saturated brine is one order of magnitude greater, so that exploiting evaporites would be a huge quasi-renewable energy source. They are also interested in salt gradient conversion when the "sea water to Dead Sea" Project is to be realized.

 

With Renaud de Richter, I am currently writing a book (in French) which will probably be named "20 energies renouvelables insolites" (20 unusual renewable energies). Salinity gradients will be the first of our 20 chapters.

 

Best regards,

 

Denis Bonnelle

Denis.B...@normalesup.org

 

 

 

 

De : geoengi...@googlegroups.com [mailto:geoengi...@googlegroups.com] De la part de Ken Caldeira
Envoyé : dimanche 7 juin 2009 22:27
À : geoengineering
Cc : Johnnie Buttram
Objet : [geo] Flooding below sea-level: Siphonics Natural Engineering (c)

[Stephen Salter]

Hi All

The most immediately expensive effect of global warming (at least to
rich people) is rising sea levels so the Buttram proposal for moving sea
water to sub-sea deserts would help.

However if you check the depth of the water table in the centre of the
Sahara, look at the likely porosity of the rock above it and the ratio
of areas of desert and sea you find that we could drain off at least one
and maybe two metres of sea level rise deep below the desert. The deep
water below the Sahara is already too saline for most uses and if you
are going to the trouble of installing solar powered desalination
equipment the extra salinity just means slightly more energy
consumption. People living in low-lying coastal cities could well afford
to give a personal desalination plant to every man, woman, child, camel
and goat in Mauritania, Mali, Niger and Chad.

The water could flow on its own if we could reduce the flow resistance
of the path between the sea bed and the deep rock below the desert.
There is a very wide range of flow resistivity in rocks. Because of the
large flow area we should be able to get sufficiently low resistance for
many rock types. I believe that resistance is dominated by ooze on the
sea bed which has clogged the entry passages into more porous material.
All we need to do is to scrape away the right amount of ooze above the
porous rock to regulate the flow and so keep sea levels where we want them.

A low carbon way to do remove ooze is to use wave energy to drag objects
which would look like a cross between a plough and an anchor through the
ooze. The ooze will be rich in nutrients and getting some of it into
suspension should help fish stocks. We can do some further un-clogging
with a vacuum mat laid on the sea bed.

The first research step would be to assemble data on rock porosity and
ooze depth in likely desert and sea areas. There may even be natural
passageways formed by rock faults. Oil companies will have lots of rock
core data and might be willing to release it. Is there one with a
sufficient level of social responsibility?

Stephen

Emeritus Professor of Engineering Design
School of Engineering and Electronics
University of Edinburgh
Mayfield Road
Edinburgh EH9 3JL
Scotland
tel +44 131 650 5704
fax +44 131 650 5702
Mobile 07795 203 195
S.Sa...@ed.ac.uk
http://www.see.ed.ac.uk/~shs

Ken Caldeira wrote:
> Folks,
>
> I ran across this pdf recommending the benefits of flooding sub
> sea-level desert areas.
>
> I believe the author of this document (cc'd) would enjoy your comments.
>
> Best,
>
> Ken
>
>
> ___________________________________________________
> Ken Caldeira
>
> Carnegie Institution Dept of Global Ecology
> 260 Panama Street, Stanford, CA 94305 USA
>

> kcal...@ciw.edu <mailto:kcal...@ciw.edu>; kcal...@stanford.edu
> <mailto:kcal...@stanford.edu>

> http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
> +1 650 704 7212; fax: +1 650 462 5968
>
>
>
> >

--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.

[dsw_s]

> The ooze will be rich in nutrients and getting some of it into
> suspension should help fish stocks.

Some, yes. But is there any guarantee that the right amount for water
flow wouldn't be enough to make dead zones?

> S.Sal...@ed.ac.ukhttp://www.see.ed.ac.uk/~shs   

>
>
>
> Ken Caldeira wrote:
> > Folks,
>
> > I ran across this pdf recommending the benefits of flooding sub
> > sea-level desert areas.
>
> > I believe the author of this document (cc'd) would enjoy your comments.
>
> > Best,
>
> > Ken
>
> > ___________________________________________________
> > Ken Caldeira
>
> > Carnegie Institution Dept of Global Ecology
> > 260 Panama Street, Stanford, CA 94305 USA
>

> > kcalde...@ciw.edu <mailto:kcalde...@ciw.edu>; kcalde...@stanford.edu
> > <mailto:kcalde...@stanford.edu>

[Andrew Lockley]

Siphoning can't work to overcome elevations of over 33'.  Shattering non-porous rocks with explosives, and blasting submarine channels or surface canals, may instead be appealing to allow direct flow.  

The soviets investigated using nuclear weapons to carry out civil engineering projects needing wide channels.

The issue of salinity is not as cut-and-dried as it might appear.  There is a potential for mixing of salt should saline and fresh waters come into contact.  This may happen by physical flow only, or assisted by osmosis - as fresh water is drawn into salty rocks.

A

2009/6/8 Stephen Salter <S.Sa...@ed.ac.uk>

[dsw_s]

What about altering circulation patterns so that rain falls where it
will fill those aquifers over the course of several years?

On Jun 9, 4:42 am, Andrew Lockley <andrew.lock...@gmail.com> wrote:
> Siphoning can't work to overcome elevations of over 33'.  Shattering
> non-porous rocks with explosives, and blasting submarine channels or surface
> canals, may instead be appealing to allow direct flow.
> The soviets investigated using nuclear weapons to carry out civil
> engineering projects needing wide channels.
>
> The issue of salinity is not as cut-and-dried as it might appear.  There is
> a potential for mixing of salt should saline and fresh waters come into
> contact.  This may happen by physical flow only, or assisted by osmosis - as
> fresh water is drawn into salty rocks.
>
> A
>

> 2009/6/8 Stephen Salter <S.Sal...@ed.ac.uk>

> > S.Sal...@ed.ac.uk

> >http://www.see.ed.ac.uk/~shs
>
> > Ken Caldeira wrote:
> > > Folks,
>
> > > I ran across this pdf recommending the benefits of flooding sub
> > > sea-level desert areas.
>
> > > I believe the author of this document (cc'd) would enjoy your comments.
>
> > > Best,
>
> > > Ken
>
> > > ___________________________________________________
> > > Ken Caldeira
>
> > > Carnegie Institution Dept of Global Ecology
> > > 260 Panama Street, Stanford, CA 94305 USA
>

> > > kcalde...@ciw.edu <mailto:kcalde...@ciw.edu>; kcalde...@stanford.edu
> > > <mailto:kcalde...@stanford.edu>