Vast Freshwater Reserves Found Beneath the Oceans
sciencedaily.com
sciencedaily.com
At the rate we are damming rivers, we will destroy many river ecosystems. This new potable water source seems less harmful than dams and could be a bridge until the energy costs of desalination are low enough.
If this discovery spurs investment in desalination (since this is simply cheaper desalination due to the lower salinity) that would be an added benefit as it would accelerate the move toward desalination.
Perhaps we could skip the dams entirely (which though seemingly renewable from a water perspective, are highly destructive to river ecosystems).
Really? You think desalination is the ultimate goal? I much prefer free, ecosystem-provided desalination (aka rooftop rain-water harvesting).
As for agricultural water use, I highly suggest picking up a copy of P.A. Yeoman's classic Water For Every Farm. It details how proper runoff management, evaporation control, and correctly-scaled earthworks can provide reliable water availability with near-zero energy inputs [other than the sun, of course].
As for dams, it's not as simple as "all dams are bad". Oversized dams that are out of scale with the local hydrology are the problem.
But, I guess some people would prefer to re-invent the Earth's water cycle!
>> I much prefer free, ecosystem-provided desalination (aka rooftop rain-water harvesting).
I agree; however, this is not an infinite supply. Taking water from rivers is effectively a form of this and it is lower cost than many other "free, ecosystem-provided desalination" since the water has already been collected into a river due to gravity and land contours. As we remove water from these 'free' sources, we are depriving an ecosystem of that water.
The worst case scenario is something like the Aral Sea http://en.wikipedia.org/wiki/Aral_Sea
I couldn't agree more.
>I agree; however, this is not an infinite supply.
Well no system can provide an infinite supply, but rainwater harvesting could support the current human population at a first-world standard of living (something our present system does not provide). Many areas famous for recent crippling droughts suffered from flooding only months before. This is a spectacular failure in water management.
As to cost, I haven't seen any comparisons of the lifetime cost of rooftop rainwater harvesting vs centralized pumped underground pipe distribution. I know rainwater harvesting is much more common in Australia, so they might have more data. I suspect it's strongly dependent on the cost of energy.
One thing I forgot to mention about desalination: current technology (specifically the Affordable Desalination Collaboration’s pilot plant) is at 30% of the thermodynamic limit. So we can expect a 3x improvement in performance, but no more. http://www.usbr.gov/research/AWT/energy_use.html
The bigger issue is actually just using waste water recycling, which is today a feasible proposition but for public perception.
Besides, don't we have enough on our plate with CO2? Sure, theoretically we could focus on both, but we seem to be doing a pretty bad job with the CO2.
Also, I'd probably rather drain these non-renewable fresh-water sources and spend the saved money on improving the quality of life of those who need it most (developing world), all the while with a long-term focus on better energy for desalination/reuse. To be fair, though, this entire paragraph is a pipe-dream.
In the case of water, which replenishes, the 'production cycle' is actually the global fresh-water cycle. If we dirty all of the fresh water faster than the earth can clean it, we're going to have to start drilling for the fossil stuff in hard-to-reach places. It's strange to think there would be drilling rigs in the ocean with people risking their lives and taking danger pay... for water. It raises a question in my mind: affordability. Who is going to be able to afford to buy all their water like this?
It's the next step now that there are several major rivers no longer reaching the ocean.
The price of water can never really climb above the price of desalination.
1. http://www.forbes.com/sites/robertbradley/2013/03/25/oil-gas... (honestly, I can't really be bothered tracking down the BLS reports.. this is the first article I found with any numbers and it reinforces what I've been told by a friend in the industry)
i guess it shouldnt be much different than oil drilling :\
"The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume."
also: http://en.wikipedia.org/wiki/Oil_platform#Deepest_oil_platfo...
either way it doesn't matter for this argument. we're talking about the difference between water and whatever it's replaced with such as "nothing" or something cheap and abundant with similar properties.
also, the water we're talking about is not itself 4 km deep. it may be under 4km of sea water, but the fresh water under the seafloor may be only 500m deep with an equivalent pressure of 4 - 4.5 km.
I'm not sure how common this is but I know Lake Michigan goes through an annual cycle where the water alternately mixes and segregates (by temperature). In the summer, the warm, less dense water rises to the top and stays there. In the winter, very cold water is actually lighter than slightly warmer water and a similar stratification happens. In spring and autumn the water temperatures near the surface equalize with water deeper in the lake and much if not all of the lake water circulates ("turns over").
Besides, once we had used that water, it would run back into the sea.
Nice link. This made me sad :'(
Push CO2, get back carbonated water? Then it is $1/liter + carbon credits for what doesn't come back up. :)
Other posters here are saying, replace it with salt water or CO2. The CO2 idea was answered. As for the "swap seawater for fresh" idea, as soon as you put a significant amount of sea water in there, you no longer have fresh water coming out! The only way to get a freshwater supply from this would be to take all it out before replacing, but then you have the "supporting the ocean bottom" problem in the interim.
Even if not, we can drill and extract fresh water at one end and pump in salt water at the other, until the water we get out becomes too saline. In porous rock the mix rate would be quite low; kind of like pumping salt water into a sponge at one end and extracting the fresh water at the other end (for a while).
This is quite a common practice in the oil industry.
Finally, salt water is more dense than fresh water. If these reservoirs underwater actually are big cavities; we can just pump salt water in the bottom and pump fresh water out the top.
NB: When I say "we can just", I mean, take a wild best guess about where the bottom and top of the well is based on crazy amounts of uncertain data extracted on a well-by-well basis.
On a serious note, this could be big. Imagine oil like drilling platforms that pump water instead. Now we only need to figure out how economical this is.
http://www.lewrockwell.com/2013/10/ryan-mcmaken/socialist-wa...