There are numerous locations around the globe
where the
Earth's
surface is below sea level. My careful analysis
suggests that
almost all of these are underwater. Just
occasionally, you can
find locations that are below sea level and are not
underwater.
Some of this is the Dutch, defying
the natural
order, but other
anomalies exist. One example is the Salton sea.
This depression
in
a dry bit of California was hilariously filled with
water by
accidentally diverting one of the world's great
rivers into it. For
a
number of reasons it has since begun to dry out
and presently
sits
as a nasty salty thing with little future.
Several people have suggested filling
depressions with seawater.
<link> The filling is always the easy part, however
the annoying
tendancy of water, and not salt, to evaporate
means that this
system
just leaves you with a shallower depression with
more salt than
before. The key is exchange. Pumping can do
this, but it's
expensive and the volumes are large. So we need
to get some,
preferably selected, water back out.
The main problem at the moment is that to get
water out, you
have to pump it UPHILL 230ft or so to sea level.
This is hard
work.
It would be much easier if the lake were AT sea
level. So let's
do
that. Now, according to one of the Salton sea
advocacy
websites,
the sea looses 360,000 gallons per year to
evaporation. This is
trivial hosepipe territory to get a net filling effect*.
The
obvious
way to fill the sea is to dig a canal from there to
the gulf of
California. This is very much shorter than the
current map
suggests. The canal only need traverse the
sections above sea
level<link> between the Salton and the Gulf.
There is only a
little
section to the west of Mexicali needed to join up
the Salton sea
and Laguna Salada, then another section from
there to the
Colorado river estuary. Total is only around 80-
150 miles of
canal.
During construction, consideration to flow
through the body of
water should be included, a way to preferentially
shepherd the
influx toward the far side of each body of water.
This could be
extremely simple,
polythene
sheet suspended from buoys with a little weight
could create a
pseudo channel within the water. So, now the
Laguna Salada is
filling with sea water. With some gates, this
should be easily
controllable at such a rate as to motivate but not
inundate
those
building the Salton-Salada canal section. Once
full, the new
inland
sea at Laguna Salada will displace... noone, no
major towns at
least.
Once high enough, water from the Laguna Salada
may start to
enter the Salton-Salada canal. Here things get a
little messy.
The
Imperial valley is populated. El Centro, Brawley
and a couple of
others, gone. Around 160,000 people total. The
dumb ones will
have to be told to move, the clever ones will be
buying land at
around sea-level elevation nearby.
Eventually we'll have a full Salton basin and a full
Laguna
Salada.
We have to build in a mechanism of water
exchange. Luckily,
the
energetics of moving water a vertical distance of
0 are pretty
good. The energetics of letting water flow
downhill are even
better. This is where tides come in. The tides in
the gulf vary
between about 1ft to 13ft above mean sea level.
If we set our
inland sea level about 3-5ft above sea level we
can have a net
inflow of water at high tide and a net outflow at
low tide. An
online calculator suggests a 10 mile canal with a
10ft head, 80ft
wide should be able to flow about 10million
gallons during the
3hrs
of high tide. There are two per day.
To prevent exchanging the same water near the
canal
repeatedly,
control of in and out flow is necessary. Even
something as
simple
as directing incoming water to the right and
allowing outflow
from the left could set up a beneficial circulation.
Or, as
mentioned a floating canal could be used to
direct fresher water
to the far side of the lake, pushing the saltier stuff
back toward
the entrance/exit. Perhaps the clever thing to do
would be to
install platforms for artificial reefs a few 100ft off
the
shoreline,
clean water could be directed between the shore
and the reef
along the periphery.
In and outflow could be managed along the same
canals since
the
tides are separated by time. Frequency of events
need not
match
between the two inland seas. The Salton-Salada
link can have
much lower capacity. Since it can open at the
same time as the
Laguna Salada-ocean link and stay open long
after it has closed.
Careful management of differential openings
could be used to
effectively flush the content using annual tidal
maxima/minima.
The complainers in the valley should remember
that this will all
happen anyway... eventually...
*obviously this will be very slow and will hit a new
equilibrium
very soon. I'm illustrating a point about scale.