But it's all uphill, isn't it?
April 14, 2010 5:12 AM Subscribe
Topher wants to know why Melbourne's water supply system doesn't include a gravity-fed pipeline from Tasmania.
But it's all uphill, isn't it?
It's not a problem of topography, it's a problem of thermodynamics.
The plans require diverting Tasmanian lake water from hydroelectric turbines which feed Melbourne with electricity to a submerged pipeline that would feed Melbourne with fresh water.
In other words, instead of using the potential energy of water stored "uphill" lake to generate electricity it will be used to "pump" water through the pipeline.
(One of the advantages for Tasmania is that Melbourne residents would pay more per liter for fresh water than for the equivalent amount of electricity generated by said liter of water.)
But the problem of thermodynamics is that the residents of Melbourne will presumably still need that electricity that is no longer being generated so instead of a desalination plant, another power plant will be has to be built.
So yeah, it's all uphill.
posted by three blind mice at 5:32 AM on April 14, 2010
It's not a problem of topography, it's a problem of thermodynamics.
The plans require diverting Tasmanian lake water from hydroelectric turbines which feed Melbourne with electricity to a submerged pipeline that would feed Melbourne with fresh water.
In other words, instead of using the potential energy of water stored "uphill" lake to generate electricity it will be used to "pump" water through the pipeline.
(One of the advantages for Tasmania is that Melbourne residents would pay more per liter for fresh water than for the equivalent amount of electricity generated by said liter of water.)
But the problem of thermodynamics is that the residents of Melbourne will presumably still need that electricity that is no longer being generated so instead of a desalination plant, another power plant will be has to be built.
So yeah, it's all uphill.
posted by three blind mice at 5:32 AM on April 14, 2010
Well presented, but he neglects to mention that both Tasmania and Victoria are upside-down.
posted by weapons-grade pandemonium at 5:33 AM on April 14, 2010 [11 favorites]
posted by weapons-grade pandemonium at 5:33 AM on April 14, 2010 [11 favorites]
the residents of Melbourne will presumably still need that electricity that is no longer being generated so instead of a desalination plant, another power plant will be has to be built.
But it sounds like they have plenty of sunshine, so is that really a problem?
posted by DU at 5:40 AM on April 14, 2010
But it sounds like they have plenty of sunshine, so is that really a problem?
posted by DU at 5:40 AM on April 14, 2010
"In other words, instead of using the potential energy of water stored "uphill" lake to generate electricity it will be used to "pump" water through the pipeline. "
That assumes you're using the same water that went through the turbines to go into the pipe. Now, it's not immediately clear to me that the 200 foot head will provide enough pressure, but the fact some water is being used for hydroelectric power shouldn't be a problem unless there's so little water in Tasmania that it's also needed to be used in Melbourne, and it doesn't sound like that's the case.
posted by edd at 5:41 AM on April 14, 2010 [1 favorite]
That assumes you're using the same water that went through the turbines to go into the pipe. Now, it's not immediately clear to me that the 200 foot head will provide enough pressure, but the fact some water is being used for hydroelectric power shouldn't be a problem unless there's so little water in Tasmania that it's also needed to be used in Melbourne, and it doesn't sound like that's the case.
posted by edd at 5:41 AM on April 14, 2010 [1 favorite]
I haven't checked, but I'm a fraction skeptical his numbers work. 200m head, for 350000m length of pipe, is a slope of 1: 0.000571429 (for 1 horizontal m, the pipe drops 0.000571429). So, not considering the pressure, it is pretty much a flat pipe.
posted by a womble is an active kind of sloth at 5:44 AM on April 14, 2010 [2 favorites]
posted by a womble is an active kind of sloth at 5:44 AM on April 14, 2010 [2 favorites]
But it sounds like they have plenty of sunshine, so is that really a problem?
Then use the sunshine to power the desalination plant.
My point is that the presentation makes it appear as though they are talking about free energy when the source of this "free" energy is already encumbered as a source of energy.
Also it is not enough to flow water through the submerged pipe, some positive pressure must be available over the pressure of seawater or there is a risk of salt water infiltration.
posted by three blind mice at 5:59 AM on April 14, 2010 [2 favorites]
Then use the sunshine to power the desalination plant.
My point is that the presentation makes it appear as though they are talking about free energy when the source of this "free" energy is already encumbered as a source of energy.
Also it is not enough to flow water through the submerged pipe, some positive pressure must be available over the pressure of seawater or there is a risk of salt water infiltration.
posted by three blind mice at 5:59 AM on April 14, 2010 [2 favorites]
Maybe they should just move Melbourne to Tasmania and get both water and electricity?
posted by Pollomacho at 6:05 AM on April 14, 2010 [1 favorite]
posted by Pollomacho at 6:05 AM on April 14, 2010 [1 favorite]
...Not building your city in a desert.
This reminds me of Los Angeles- stealing your water from someplace else.
posted by MtDewd at 6:05 AM on April 14, 2010
This reminds me of Los Angeles- stealing your water from someplace else.
posted by MtDewd at 6:05 AM on April 14, 2010
Then use the sunshine to power the desalination plant.
Is that the same as the amount of power they'd be "missing" by running through the generator?
...some positive pressure must be available over the pressure of seawater or there is a risk of salt water infiltration.
He said the maximum depth of the sea is 75m whereas the head is 200m, so that's already done.
posted by DU at 6:16 AM on April 14, 2010
Is that the same as the amount of power they'd be "missing" by running through the generator?
...some positive pressure must be available over the pressure of seawater or there is a risk of salt water infiltration.
He said the maximum depth of the sea is 75m whereas the head is 200m, so that's already done.
posted by DU at 6:16 AM on April 14, 2010
Maybe they should just move Melbourne to Tasmania and get both water and electricity?
Either you bring the water to L.A. or you bring L.A. to the water.
posted by pracowity at 6:18 AM on April 14, 2010
Either you bring the water to L.A. or you bring L.A. to the water.
posted by pracowity at 6:18 AM on April 14, 2010
In my mind anything encouraging humans to be less conscious of water use is a bad thing. Melbourne has some major water issues, for sure. But solving those issues (if the pipe worked) is only going to encourage people to use more water - and let more people move to Melbourne - which will end up stressing the system again.
Water problems are fairly simple in concept: Don't take out more than the environment puts back every year. In execution, however, we generally screw it up. We like to irrigate, take long showers, and live in large communities that are often nowhere near sources of fresh water big enough to support the population. Salt Lake City, LA, Denver, New York, Melbourne... you can rattle off a list pretty easily. All have major water issues; some are manageable, some are not, and all are going to be an even bigger problem in the future.
posted by caution live frogs at 6:20 AM on April 14, 2010
Water problems are fairly simple in concept: Don't take out more than the environment puts back every year. In execution, however, we generally screw it up. We like to irrigate, take long showers, and live in large communities that are often nowhere near sources of fresh water big enough to support the population. Salt Lake City, LA, Denver, New York, Melbourne... you can rattle off a list pretty easily. All have major water issues; some are manageable, some are not, and all are going to be an even bigger problem in the future.
posted by caution live frogs at 6:20 AM on April 14, 2010
How, exactly, is Melbourne, Australia, built in a desert?
posted by Wolof at 6:29 AM on April 14, 2010
posted by Wolof at 6:29 AM on April 14, 2010
Desalination has massive advantages over developing new freshwater resources, especially in coastal areas. The two main problems with desalination via reverse osmosis are:
1. Higher treatment costs.
2. Disposal of concentrated brine.
Problem 2 is pretty easily solveable. Concentrated brine can be mixed with treated wastewater to bring the salt concentrations down to ambient levels. 1 is more difficult, but it's getting cheaper all the time.
posted by electroboy at 6:46 AM on April 14, 2010
1. Higher treatment costs.
2. Disposal of concentrated brine.
Problem 2 is pretty easily solveable. Concentrated brine can be mixed with treated wastewater to bring the salt concentrations down to ambient levels. 1 is more difficult, but it's getting cheaper all the time.
posted by electroboy at 6:46 AM on April 14, 2010
How, exactly, is Melbourne, Australia, built in a desert?
Desert or no desert, the premise is sound: "Don't take out more than the environment puts back every year."
If you start sucking water out of Tasmania now so Melburnians can have big lawns and hour showers, what are you going to do in 10 or 20 years when Tasmanians decide that they need that water after all, or that they need to charge ten times as much for it, but Melburnians decide they need even more water than they do now? Fight? A more reasonable goal would be to make Melburnians twice as efficient so the city could support twice as many.
posted by pracowity at 6:55 AM on April 14, 2010
Desert or no desert, the premise is sound: "Don't take out more than the environment puts back every year."
If you start sucking water out of Tasmania now so Melburnians can have big lawns and hour showers, what are you going to do in 10 or 20 years when Tasmanians decide that they need that water after all, or that they need to charge ten times as much for it, but Melburnians decide they need even more water than they do now? Fight? A more reasonable goal would be to make Melburnians twice as efficient so the city could support twice as many.
posted by pracowity at 6:55 AM on April 14, 2010
In my mind anything encouraging humans to be less conscious of water use is a bad thing. Melbourne has some major water issues, for sure. But solving those issues (if the pipe worked) is only going to encourage people to use more water - and let more people move to Melbourne - which will end up stressing the system again.
You make it sound like Melbourne's current water woes are keeping people from moving to Melbourne. Let me assure you, it is not. Melbourne is expanding at a rate of 1700 people per week. I don't live there, but I think I can confidently say "the system" is more than just stressed right now.
Water shortage isn't just Melbourne's issue. It's a national concern. No place in Australia is truly near sufficiently large water supplies, because no such vast supply exists (with the exception of Tasmania, perhaps, but then again Tasmania's population is pretty small). We don't have a Yangtze, an Amazon, a Nile, or a Mississippi. We have the Murray–Darling, which is is already overused.
The nation's population continues to grow and all of the cities are expanding. Everyone worries about water. Water desalination plants are being built in many states. Queensland has begun recycling water (something we should all have been doing a long time ago). South Australia, which has it much worse than Victoria, has already been upping the price of water (it used to be free, once upon a time) to reduce usage (economic incentives tend to be more powerful than moral ones).
But at the end of the day, there's a feeling here that the entire situation will soon be completely untenable. A lot of changes need to occur across the entire continent if we're going to reach a sustainable situation.
Novel solutions such as those being proposed in the linked video are welcome news, but I agree that better conservation practices need to be adopted if any true solution is to be found.
posted by kisch mokusch at 7:21 AM on April 14, 2010 [1 favorite]
You make it sound like Melbourne's current water woes are keeping people from moving to Melbourne. Let me assure you, it is not. Melbourne is expanding at a rate of 1700 people per week. I don't live there, but I think I can confidently say "the system" is more than just stressed right now.
Water shortage isn't just Melbourne's issue. It's a national concern. No place in Australia is truly near sufficiently large water supplies, because no such vast supply exists (with the exception of Tasmania, perhaps, but then again Tasmania's population is pretty small). We don't have a Yangtze, an Amazon, a Nile, or a Mississippi. We have the Murray–Darling, which is is already overused.
The nation's population continues to grow and all of the cities are expanding. Everyone worries about water. Water desalination plants are being built in many states. Queensland has begun recycling water (something we should all have been doing a long time ago). South Australia, which has it much worse than Victoria, has already been upping the price of water (it used to be free, once upon a time) to reduce usage (economic incentives tend to be more powerful than moral ones).
But at the end of the day, there's a feeling here that the entire situation will soon be completely untenable. A lot of changes need to occur across the entire continent if we're going to reach a sustainable situation.
Novel solutions such as those being proposed in the linked video are welcome news, but I agree that better conservation practices need to be adopted if any true solution is to be found.
posted by kisch mokusch at 7:21 AM on April 14, 2010 [1 favorite]
Wait. Just because the river in Taz is 200m above sea level doesn't mean the water will drop 200m to Melbourne. The curvature of the earth would balance it out at some point. Obviously those places aren't far enough apart to make it a zero degree grade, but it would reduce that 200m by some amount, right? I mean, we're not talking about a flat plain here.
posted by (Arsenio) Hall and (Warren) Oates at 7:45 AM on April 14, 2010
posted by (Arsenio) Hall and (Warren) Oates at 7:45 AM on April 14, 2010
As far as water is concerned, sea level all around the world is a flat plain. (*) It's all at the same gravitational potential. Yes, if Superman were standing in Tasmania it would look as though Melbourne were "down" the curved side of the earth. But if he were standing in Melbourne it would look as though Tasmania were down!
(*) ignoring quibbles about atmospheric pressure.
posted by Joe in Australia at 8:06 AM on April 14, 2010 [1 favorite]
(*) ignoring quibbles about atmospheric pressure.
posted by Joe in Australia at 8:06 AM on April 14, 2010 [1 favorite]
Don't take out more than the environment puts back every year.
Civilisations have been channelling water from once place to another for millennia. Often the best place for a settlement isn't the place with the best water supply. So people move water from wherever there's planty to wherever there's a shortfall. The Romans did it all the time, although their undersea pipe technology wasn't so good.
Overall, the plan is not to take out more than is put into the environment, except in a localised sense. It just happens that 99% (according to one estimate) of the water entering the rivers in NW Tasmania is just flowing out to sea.
And ensuring an adequate supply of water to a city and reducing waste don't have to be mutually exclusive.
posted by le morte de bea arthur at 8:41 AM on April 14, 2010 [1 favorite]
Civilisations have been channelling water from once place to another for millennia. Often the best place for a settlement isn't the place with the best water supply. So people move water from wherever there's planty to wherever there's a shortfall. The Romans did it all the time, although their undersea pipe technology wasn't so good.
Overall, the plan is not to take out more than is put into the environment, except in a localised sense. It just happens that 99% (according to one estimate) of the water entering the rivers in NW Tasmania is just flowing out to sea.
And ensuring an adequate supply of water to a city and reducing waste don't have to be mutually exclusive.
posted by le morte de bea arthur at 8:41 AM on April 14, 2010 [1 favorite]
Novel solutions such as those being proposed in the linked video are welcome news
I guess, except that's it's not really novel. Snatching water from the neighbors is the oldest trick in the book.
Novel would be something like turning all that damned burning sun and salty ocean into drinkable water using an almost passive system - minimal pumping, minimal electricity, just some kind of vast seaside construction with few or no moving parts. Take water in at high tide, let it run through something that filters everything larger than a certain size out of the water, and leave the filtered water in an underground reservoir. It would require some mighty big filters, and of course they'd have to be made and cleaned or replaced actively, not passively, but something like that seems the best goal, because the sun and the ocean and tides are right there for almost everyone to use.
posted by pracowity at 8:51 AM on April 14, 2010
I guess, except that's it's not really novel. Snatching water from the neighbors is the oldest trick in the book.
Novel would be something like turning all that damned burning sun and salty ocean into drinkable water using an almost passive system - minimal pumping, minimal electricity, just some kind of vast seaside construction with few or no moving parts. Take water in at high tide, let it run through something that filters everything larger than a certain size out of the water, and leave the filtered water in an underground reservoir. It would require some mighty big filters, and of course they'd have to be made and cleaned or replaced actively, not passively, but something like that seems the best goal, because the sun and the ocean and tides are right there for almost everyone to use.
posted by pracowity at 8:51 AM on April 14, 2010
Pretty arrogant to argue that an undersea pipeline should be built and hydrology altered because, you know, Melbourne needs water.
posted by KokuRyu at 9:03 AM on April 14, 2010
posted by KokuRyu at 9:03 AM on April 14, 2010
A lot of changes need to occur across the entire continent if we're going to reach a sustainable situation.
For example: Stop planting lawns that require large amounts of water that you don't have to thrive.
posted by eriko at 9:03 AM on April 14, 2010
For example: Stop planting lawns that require large amounts of water that you don't have to thrive.
posted by eriko at 9:03 AM on April 14, 2010
Pretty arrogant to argue that an undersea pipeline should be built and hydrology altered because, you know, Melbourne needs water.
On that basis, pretty much all human activity since we first ploughed a field is 'arrogant'. Piping a bit of water a few hundred miles is pretty low on the scale of terrible things humans have done to nature.
posted by le morte de bea arthur at 9:18 AM on April 14, 2010 [1 favorite]
On that basis, pretty much all human activity since we first ploughed a field is 'arrogant'. Piping a bit of water a few hundred miles is pretty low on the scale of terrible things humans have done to nature.
posted by le morte de bea arthur at 9:18 AM on April 14, 2010 [1 favorite]
On that basis, pretty much all human activity since we first ploughed a field is 'arrogant'. Piping a bit of water a few hundred miles is pretty low on the scale of terrible things humans have done to nature.
We're not talking a bit of water here, we're talking about a city that consumes billions of liters a day. Try and diminish it all you want, but this is a city of four million in an area that only gets two inches of rain per month.
posted by ged at 9:34 AM on April 14, 2010
We're not talking a bit of water here, we're talking about a city that consumes billions of liters a day. Try and diminish it all you want, but this is a city of four million in an area that only gets two inches of rain per month.
posted by ged at 9:34 AM on April 14, 2010
We're not talking a bit of water here
But we are, really, because that amount of water is a small fraction (1% in one proposal I read) of the water that would otherwise just end up flowing into the sea.
posted by le morte de bea arthur at 9:49 AM on April 14, 2010 [2 favorites]
But we are, really, because that amount of water is a small fraction (1% in one proposal I read) of the water that would otherwise just end up flowing into the sea.
posted by le morte de bea arthur at 9:49 AM on April 14, 2010 [2 favorites]
But we are, really, because that amount of water is a small fraction (1% in one proposal I read) of the water that would otherwise just end up flowing into the sea.
Everything is interconnected blah blah blah...
Say, did you see where the Aral Sea went? I stepped out for a moment and when I came back 80% of it was gone.
posted by KokuRyu at 10:25 AM on April 14, 2010 [2 favorites]
Everything is interconnected blah blah blah...
Say, did you see where the Aral Sea went? I stepped out for a moment and when I came back 80% of it was gone.
posted by KokuRyu at 10:25 AM on April 14, 2010 [2 favorites]
2. Disposal of concentrated brine.
Problem 2 is pretty easily solveable. Concentrated brine can be mixed with treated wastewater to bring the salt concentrations down to ambient levels.
I've been reading quite a bit about salt lately (largely, the acquiring of it). I take it we're talking about far too much to be useful for salt production?
posted by Durn Bronzefist at 11:01 AM on April 14, 2010
Problem 2 is pretty easily solveable. Concentrated brine can be mixed with treated wastewater to bring the salt concentrations down to ambient levels.
I've been reading quite a bit about salt lately (largely, the acquiring of it). I take it we're talking about far too much to be useful for salt production?
posted by Durn Bronzefist at 11:01 AM on April 14, 2010
Say, did you see where the Aral Sea went? I stepped out for a moment and when I came back 80% of it was gone.
And so, logically, losing 1% of the fresh water flowing into the Indian Ocean from a particular river in Tasmania will cause the entire Indian Ocean, and by extension, the Pacific and Atlantic, to shrink?
I'm not sure where exactly you see the equivalence.
posted by le morte de bea arthur at 11:15 AM on April 14, 2010 [1 favorite]
And so, logically, losing 1% of the fresh water flowing into the Indian Ocean from a particular river in Tasmania will cause the entire Indian Ocean, and by extension, the Pacific and Atlantic, to shrink?
I'm not sure where exactly you see the equivalence.
posted by le morte de bea arthur at 11:15 AM on April 14, 2010 [1 favorite]
Yeah, it's quite a lot of salt. You certainly can divert some of it for industrial salt production, but you'd be getting somewhere in the neighborhood of 35g/L of treated water, so I guess it depends on your local demand for salt. Also, you're not getting dry salt, you're getting a concentrated brine solution that's about twice the salinity of regular seawater. Some RO plants don't dilute the brine they discharge into the ocean, as I don't think there are any studies showing any negative consequences (massive dilution), but you know how that sort of thing goes. Better to mix it with wastewater that's been well treated and remove the unintended consequences.
posted by electroboy at 11:29 AM on April 14, 2010
posted by electroboy at 11:29 AM on April 14, 2010
I have not read any actual engineering reports, and am not qualified to evaluate the idea on anything the the most basic technical level, but it is strange to see such kneejerk negative responses here. By any measure, desalination is currently a terrible choice. It's expensive and uses huge amounts of energy. Almost none of the objections on this page make sense.
It is not at all obvious that this would compete with water used for hydroelectricity. In fact, with the stated number of 7% of yearly flow, it does not seem likely to be a problem.
The slope of the pipe doesn't really matter as long as it is down hill. And the idea that the curvature of the earth would balance it out would only make sense if you believed that Australians were actually hanging on upside-down.
With 200 meters head, the water in the pipe will indeed be pressurized more than the surrounding seawater.
And the idea that solving a water crisis would just encourage people to be wasteful is kind of dumb, and rather callous. Easy to say living somewhere that has not had a multi-decade drought.
posted by Nothing at 11:31 AM on April 14, 2010 [3 favorites]
It is not at all obvious that this would compete with water used for hydroelectricity. In fact, with the stated number of 7% of yearly flow, it does not seem likely to be a problem.
The slope of the pipe doesn't really matter as long as it is down hill. And the idea that the curvature of the earth would balance it out would only make sense if you believed that Australians were actually hanging on upside-down.
With 200 meters head, the water in the pipe will indeed be pressurized more than the surrounding seawater.
And the idea that solving a water crisis would just encourage people to be wasteful is kind of dumb, and rather callous. Easy to say living somewhere that has not had a multi-decade drought.
posted by Nothing at 11:31 AM on April 14, 2010 [3 favorites]
And so, logically, losing 1% of the fresh water flowing into the Indian Ocean from a particular river in Tasmania will cause the entire Indian Ocean, and by extension, the Pacific and Atlantic, to shrink?
Well, first of all, the "a small fraction (1% in one proposal I read) of the water that would otherwise just end up flowing into the sea" is not just flowing into the sea. It's part of an ecology, and modifying an ecology will always have consequences. Not to sound like a junior high school science teacher or a dirty hippy or whatever, but "everything is connected". The water flowing into the sea is not being wasted. To think otherwise is pretty arrogant. Sure, not an environmental crime as great as diverting major rivers to irrigate a cotton industry and drain the Aral Sea, but we all need to make changes in the coming decades if we want to preserve our civilization on the planet. Diverting rivers to water lawns and fill swimming pools is not the way to go.
Second, where do you get this "1%" figure from?
posted by KokuRyu at 11:33 AM on April 14, 2010
Well, first of all, the "a small fraction (1% in one proposal I read) of the water that would otherwise just end up flowing into the sea" is not just flowing into the sea. It's part of an ecology, and modifying an ecology will always have consequences. Not to sound like a junior high school science teacher or a dirty hippy or whatever, but "everything is connected". The water flowing into the sea is not being wasted. To think otherwise is pretty arrogant. Sure, not an environmental crime as great as diverting major rivers to irrigate a cotton industry and drain the Aral Sea, but we all need to make changes in the coming decades if we want to preserve our civilization on the planet. Diverting rivers to water lawns and fill swimming pools is not the way to go.
Second, where do you get this "1%" figure from?
posted by KokuRyu at 11:33 AM on April 14, 2010
KokuRyu, that is a good point, these things do not happen in a vacuum, and we need to keep that in mind. The problem we face now as a species is that there are so many of us that anything we do is going to have serious consequences, and that means we have to be careful. It also means that these kinds of questions are always going to come down to weighing the impact of our options.
A good example of this is compact fluorescent bulbs. A great idea! But you make a billion of them and you've got a lot of mercury floating around. Is that a worthwhile tradeoff? Probably, yes. But it is a tradeoff.
The real problem comes when people see that all options have costs, and so assume that the best option is to do nothing. Unfortunately, this often carries a very high cost of its own.
Is this pipeline idea better than energy intensive desalination, and the continuing stress on the local river system? I don't know. It sounds like it to me, but I don't have enough information right now. But pointing out that there will be an impact to piping the water is kind of pointless. We know there will be an impact, the question is will it be a better option.
posted by Nothing at 12:02 PM on April 14, 2010 [1 favorite]
A good example of this is compact fluorescent bulbs. A great idea! But you make a billion of them and you've got a lot of mercury floating around. Is that a worthwhile tradeoff? Probably, yes. But it is a tradeoff.
The real problem comes when people see that all options have costs, and so assume that the best option is to do nothing. Unfortunately, this often carries a very high cost of its own.
Is this pipeline idea better than energy intensive desalination, and the continuing stress on the local river system? I don't know. It sounds like it to me, but I don't have enough information right now. But pointing out that there will be an impact to piping the water is kind of pointless. We know there will be an impact, the question is will it be a better option.
posted by Nothing at 12:02 PM on April 14, 2010 [1 favorite]
I have not read any actual engineering reports, and am not qualified to evaluate the idea on anything the the most basic technical level
I haven't read one, but I did write one a few months ago, evaluating a coastal communities options for future water supplies. RO finished high up on the list. Expensive, yes, but it's also a guaranteed source. Annual variability in rainfall, upstream use and the possibility of contamination are all risk factors that are difficult to plan for.
By any measure, desalination is currently a terrible choice.
It really isn't. It's certainly more expensive and uses more energy, but what are your options? There's a finite amount of fresh water, and you can only use so much of it before you absolutely destroy the chemistry of natural waters. What if there's a change in regulation or an endangered species discovered? What if the watershed owner wants to renegotiate your drawing rights lease? Municipalities have a strong interest in long term sustainability for water supply, because it takes many years to find and develop new fresh water sources.
posted by electroboy at 12:07 PM on April 14, 2010
I haven't read one, but I did write one a few months ago, evaluating a coastal communities options for future water supplies. RO finished high up on the list. Expensive, yes, but it's also a guaranteed source. Annual variability in rainfall, upstream use and the possibility of contamination are all risk factors that are difficult to plan for.
By any measure, desalination is currently a terrible choice.
It really isn't. It's certainly more expensive and uses more energy, but what are your options? There's a finite amount of fresh water, and you can only use so much of it before you absolutely destroy the chemistry of natural waters. What if there's a change in regulation or an endangered species discovered? What if the watershed owner wants to renegotiate your drawing rights lease? Municipalities have a strong interest in long term sustainability for water supply, because it takes many years to find and develop new fresh water sources.
posted by electroboy at 12:07 PM on April 14, 2010
Also, you're not getting dry salt, you're getting a concentrated brine solution that's about twice the salinity of regular seawater.
Concentrated brine is the intermediate step in (non-mine) salt production since antiquity. But I could see how an operation like this might outstrip demand. Still, it's not waste; there's a product to be had. But sure, simple release could be problematic.
As for efficiency, I thought Aussies/Kiwis were way ahead of us North Americans, at least in terms of energy conservation; not so sure about water. Then again, you have to work with what you have. It's pretty easy to ignore the waste of water in Canada, at present at least.
posted by Durn Bronzefist at 12:08 PM on April 14, 2010
Concentrated brine is the intermediate step in (non-mine) salt production since antiquity. But I could see how an operation like this might outstrip demand. Still, it's not waste; there's a product to be had. But sure, simple release could be problematic.
As for efficiency, I thought Aussies/Kiwis were way ahead of us North Americans, at least in terms of energy conservation; not so sure about water. Then again, you have to work with what you have. It's pretty easy to ignore the waste of water in Canada, at present at least.
posted by Durn Bronzefist at 12:08 PM on April 14, 2010
Yeah, there's low energy ways of getting dry salt (i.e. massive evap ponds), but you've got to have a place to put it. Given that you're always going to have a stream of wastewater to dilute it with, it solves the storage problem pretty neatly.
Concentrated brine is still a primary step in salt mining.
Aussies do quite a bit of wastewater reuse and I believe they run nonpotable municipal water lines for things like watering your lawn, industrial processes and other nonconsumption type uses. It saves quite a bit of energy and expense, but it's gotten limited penetration in the US, since you need to run dedicated supply lines to get it to the end user.
posted by electroboy at 12:20 PM on April 14, 2010
Concentrated brine is still a primary step in salt mining.
Aussies do quite a bit of wastewater reuse and I believe they run nonpotable municipal water lines for things like watering your lawn, industrial processes and other nonconsumption type uses. It saves quite a bit of energy and expense, but it's gotten limited penetration in the US, since you need to run dedicated supply lines to get it to the end user.
posted by electroboy at 12:20 PM on April 14, 2010
I overstated in saying it was a terrible choice, but energy intensive is a pretty big negative, both in terms of cost and environmental impact. "What are your options" is exactly the point. In this case, there seems to be a better option.
posted by Nothing at 1:05 PM on April 14, 2010
posted by Nothing at 1:05 PM on April 14, 2010
For example, the pipeline appears to be about 50% more expensive than building the RO plant, and the RO plant guarantees a water source, whereas a river in Tasmania works until you get a protracted drought, someone exerts prior drawing rights, or your local environmental protection agency finds a snail darter or spotted owl. Also consider that the cost of the pipeline is only a means of conveyance, the water still has to be treated, and the cost of that depends on the initial quality of the river water.
Certainly I wouldn't disagree that the energy cost has a significant environmental impact, but it also depends where you get your energy from.
Also, it appears timing is an issue. The RO plant could be up and running much sooner than the pipeline and expanded treatment plant could be built.
Again, these options are rarely as simple as presented. RO is certainly more expensive initially than conventional treatment, but conventional treatment and supply takes advantage of a lot of externalities that aren't usually accounted for, like environmental impact.
posted by electroboy at 2:32 PM on April 14, 2010 [1 favorite]
Certainly I wouldn't disagree that the energy cost has a significant environmental impact, but it also depends where you get your energy from.
Also, it appears timing is an issue. The RO plant could be up and running much sooner than the pipeline and expanded treatment plant could be built.
Again, these options are rarely as simple as presented. RO is certainly more expensive initially than conventional treatment, but conventional treatment and supply takes advantage of a lot of externalities that aren't usually accounted for, like environmental impact.
posted by electroboy at 2:32 PM on April 14, 2010 [1 favorite]
Have the people commenting about lawns and swimming pools ever actually been to Melbourne? Or looked at an aerial photo of Melbourne? Its not Las Vegas.
These are the current water restrictions already in place, by the way.
posted by PercyByssheShelley at 2:51 PM on April 14, 2010
These are the current water restrictions already in place, by the way.
posted by PercyByssheShelley at 2:51 PM on April 14, 2010
As a Melbourne resident with roots in Queensland, I'd like to say what fucking burning sunlight?
it's been overcast and drizzling for a week now and I'm going a little crazy
posted by geek anachronism at 4:20 PM on April 14, 2010
it's been overcast and drizzling for a week now and I'm going a little crazy
posted by geek anachronism at 4:20 PM on April 14, 2010
Aussies do quite a bit of wastewater reuse and I believe they run nonpotable municipal water lines for things like watering your lawn, industrial processes and other nonconsumption type uses.
I don't think that's right actually - I haven't heard of a single large municipal council that does that.
Rainwater tanks in Adelaide are pretty much de rigeur, and are becoming much more common in Melbourne thanks to the prolonged drought. There was a proposal somewhere in Queensland to start recycling wastewater but it was dropped after a community backlash. I do think though that this will eventually start to happen all around the country.
posted by awfurby at 4:32 PM on April 14, 2010
I don't think that's right actually - I haven't heard of a single large municipal council that does that.
Rainwater tanks in Adelaide are pretty much de rigeur, and are becoming much more common in Melbourne thanks to the prolonged drought. There was a proposal somewhere in Queensland to start recycling wastewater but it was dropped after a community backlash. I do think though that this will eventually start to happen all around the country.
posted by awfurby at 4:32 PM on April 14, 2010
awfurby: There was a proposal somewhere in Queensland to start recycling wastewater but it was dropped after a community backlash. I do think though that this will eventually start to happen all around the country.
Toowoomba. It was defeated in part due to the 'we don't want to be known at Poowoomba' activists but when they full on ran out of water, it was put in place anyway. It's a special sort of case in that Toowoomba is on a plateau so water is a problem at the best of times. Add to that a culture of gardening (they do a festival of flowers) and you get a whole bunch of issues.
And yeah, I've not heard of a council doing wastewater/grey water but they do allow for/rebate personal hookups.
posted by geek anachronism at 4:43 PM on April 14, 2010
Toowoomba. It was defeated in part due to the 'we don't want to be known at Poowoomba' activists but when they full on ran out of water, it was put in place anyway. It's a special sort of case in that Toowoomba is on a plateau so water is a problem at the best of times. Add to that a culture of gardening (they do a festival of flowers) and you get a whole bunch of issues.
And yeah, I've not heard of a council doing wastewater/grey water but they do allow for/rebate personal hookups.
posted by geek anachronism at 4:43 PM on April 14, 2010
There seems to be a lot of negativity about the idea, specifically it's potential for negative ecological impacts to Tasmania.
But the other side of the coin is, what are the positive ecological benefits to the Murray Darling; for NSW, Victoria, and South Australia? Isn't it possible that the ecological benefits outweigh the drawbacks in this instance?
Of course a lot more data is needed, and it should still be done in conjunction with water use reform (in the agricultural sector too, Melbourne isn't the only place taking water from our river systems)....
Also about not building cities in arid areas: hindsight is 20/20 isn't it?
e.g. our agriculture was based on what grew in a European climate, with European rainfalls and soil. Grazing sheep and cattle too. Farmers were penalised if they didn't clear their land of trees. So now we have problems with salinity and poor soil quality, erosion, and water shortages.
Melbourne isn't going to move any time soon. We just have to make the best of a bad situation.
posted by joz at 5:31 PM on April 14, 2010
But the other side of the coin is, what are the positive ecological benefits to the Murray Darling; for NSW, Victoria, and South Australia? Isn't it possible that the ecological benefits outweigh the drawbacks in this instance?
Of course a lot more data is needed, and it should still be done in conjunction with water use reform (in the agricultural sector too, Melbourne isn't the only place taking water from our river systems)....
Also about not building cities in arid areas: hindsight is 20/20 isn't it?
e.g. our agriculture was based on what grew in a European climate, with European rainfalls and soil. Grazing sheep and cattle too. Farmers were penalised if they didn't clear their land of trees. So now we have problems with salinity and poor soil quality, erosion, and water shortages.
Melbourne isn't going to move any time soon. We just have to make the best of a bad situation.
posted by joz at 5:31 PM on April 14, 2010
There's some serious ignorance going on in this thread.
But, gah, just looked at my clock and realised I don't have time to write anything long.
So, just a few quick points.
the desal plant is going to run on wind power, so no carbon emissions.
It's going to cost up to $4bn, which is really quite a lot of money if you ask me.
Melburnians are really quite efficient water users, at ~150 litres per day. This is a 25%+ drop PER CAPITA over the last decade. There are still some easy efficiencies to be gained, however.
Rainwater tanks are a bit of a chimera. I think they should be compulsory in new detached dwellings, but they're very expensive to retrofit, dangerous to human health if you drink from them without precautions and only really help with the garden and toilet. A partial solution only.
The purported costs for the pipe from tassie are bullshit. Ken Davidson doesn't know what he's talking about. GHD looked at this and reckon it would be at least $3bn.
Tassie has droughts too you know.
Tassie provincial politics would allow them to sell us the water.
Melbourne is now connected to the Murray Darling, but it's not a big connection, doesn't have much bearing on the health of this system or on water availability for Adelaide.
Domestic water use is only 8% of total consumption. Overwhelming water consumption is from irrigated agriculture. Banging on about how much those evil city-dwellers use is a complete distraction.
posted by wilful at 6:35 PM on April 14, 2010 [3 favorites]
But, gah, just looked at my clock and realised I don't have time to write anything long.
So, just a few quick points.
the desal plant is going to run on wind power, so no carbon emissions.
It's going to cost up to $4bn, which is really quite a lot of money if you ask me.
Melburnians are really quite efficient water users, at ~150 litres per day. This is a 25%+ drop PER CAPITA over the last decade. There are still some easy efficiencies to be gained, however.
Rainwater tanks are a bit of a chimera. I think they should be compulsory in new detached dwellings, but they're very expensive to retrofit, dangerous to human health if you drink from them without precautions and only really help with the garden and toilet. A partial solution only.
The purported costs for the pipe from tassie are bullshit. Ken Davidson doesn't know what he's talking about. GHD looked at this and reckon it would be at least $3bn.
Tassie has droughts too you know.
Tassie provincial politics would allow them to sell us the water.
Melbourne is now connected to the Murray Darling, but it's not a big connection, doesn't have much bearing on the health of this system or on water availability for Adelaide.
Domestic water use is only 8% of total consumption. Overwhelming water consumption is from irrigated agriculture. Banging on about how much those evil city-dwellers use is a complete distraction.
posted by wilful at 6:35 PM on April 14, 2010 [3 favorites]
I haven't checked, but I'm a fraction skeptical his numbers work. 200m head, for 350000m length of pipe, is a slope of 1: 0.000571429 (for 1 horizontal m, the pipe drops 0.000571429). So, not considering the pressure, it is pretty much a flat pipe.
Plenty of rivers have gradients of less than a metre per kilometre, it's enough to get water moving.
posted by L.P. Hatecraft at 7:15 PM on April 14, 2010
Plenty of rivers have gradients of less than a metre per kilometre, it's enough to get water moving.
posted by L.P. Hatecraft at 7:15 PM on April 14, 2010
...Not building your city in a desert.
City? What about the entire country?
Not that Aussies haven't done fantastic things with what they have, but with the exception of strips along the coasts, the whole continent is an arid emptiness, largely unsuitable for agriculture, and they're lucky if they haven't overfarmed/overgrazed the limited suitable land already.
Anyway, I'm hardly surprised this is being talked about, in an era when China is engaged in the largest water-management engineering projects in human history. I would even bet that the outcome, in a 10 or 20 year timeframe, is that both the desal plant and this pipeline get built.
posted by dhartung at 9:34 PM on April 14, 2010
City? What about the entire country?
Not that Aussies haven't done fantastic things with what they have, but with the exception of strips along the coasts, the whole continent is an arid emptiness, largely unsuitable for agriculture, and they're lucky if they haven't overfarmed/overgrazed the limited suitable land already.
Anyway, I'm hardly surprised this is being talked about, in an era when China is engaged in the largest water-management engineering projects in human history. I would even bet that the outcome, in a 10 or 20 year timeframe, is that both the desal plant and this pipeline get built.
posted by dhartung at 9:34 PM on April 14, 2010
who is this topher fellow and why does he think he's funny?
many pseudo/almost/diverting-but-not-relevant facts quoted there.
posted by wilful at 5:10 AM on April 15, 2010
many pseudo/almost/diverting-but-not-relevant facts quoted there.
posted by wilful at 5:10 AM on April 15, 2010
Plenty of rivers have gradients of less than a metre per kilometre, it's enough to get water moving.
Of course it will move, it's whether or not it will move at the rate you want it to.
posted by electroboy at 6:42 AM on April 15, 2010
Of course it will move, it's whether or not it will move at the rate you want it to.
posted by electroboy at 6:42 AM on April 15, 2010
I admit I haven't watched the video, but 200 m of head sounds like it's talking about pump head, not elevation. But then, that was the fluids test I did worst on. (Gallons per minute versus pump head versus pump efficiency)
posted by rubah at 11:10 PM on April 15, 2010
posted by rubah at 11:10 PM on April 15, 2010
I am very skeptical that the desal plant will end up running on wind power; the Brumby government is very fond of wind power because they love to watch things spin.
What I am expecting to see is Brumby pointing to wind generators with nameplate ratings of maybe 100MW and claiming that these offset the desal plant's expected 90-120MW energy consumption, which of course it will not get anywhere near doing due to wind's relatively low capacity factor.
Also, if Brumby or Holding ever makes any public statement comparing the costs of a Tasmanian pipeline with that of the desal plant (which they are, in my opinion, quite unlikely to do) you can bet they won't be doing that on the basis of average cost per delivered gigalitre amortized over the project's expected service life. Their numbers will conveniently forget about the construction cost of the offset wind farm and the ongoing maintenance and running costs of the desal plant, and they will pull a vastly inflated pipeline construction cost figure straight out of their arses. You watch them.
posted by flabdablet at 5:47 AM on April 16, 2010
What I am expecting to see is Brumby pointing to wind generators with nameplate ratings of maybe 100MW and claiming that these offset the desal plant's expected 90-120MW energy consumption, which of course it will not get anywhere near doing due to wind's relatively low capacity factor.
Also, if Brumby or Holding ever makes any public statement comparing the costs of a Tasmanian pipeline with that of the desal plant (which they are, in my opinion, quite unlikely to do) you can bet they won't be doing that on the basis of average cost per delivered gigalitre amortized over the project's expected service life. Their numbers will conveniently forget about the construction cost of the offset wind farm and the ongoing maintenance and running costs of the desal plant, and they will pull a vastly inflated pipeline construction cost figure straight out of their arses. You watch them.
posted by flabdablet at 5:47 AM on April 16, 2010
Based on some other tunneling jobs I've worked on, $10-12 billion for 200 miles of pipeline is probably about right. Given that most tunneling machines can do about 50 feet on a good day, it's going to require a huge number of machines (roughly $1-2 million each) running around the clock, not to mention that you have to provide access and then restore a construction site stretching over 200 miles. A gravity pipeline may seem simple compared to a desalination plant, but the design, permitting and construction is anything but. I'm just completing a 12,000 foot gravity sewer pipeline design, and that's taken a year to complete.
posted by electroboy at 6:17 AM on April 16, 2010
posted by electroboy at 6:17 AM on April 16, 2010
Why tunnel? Why not just weld a pipe in sections and lay it off the back of a barge?
posted by flabdablet at 8:33 AM on April 16, 2010
posted by flabdablet at 8:33 AM on April 16, 2010
You might be able to. Depends on how deep the channel is, pipe material, local currents and a bunch of other factors.
posted by electroboy at 9:41 AM on April 16, 2010
posted by electroboy at 9:41 AM on April 16, 2010
Wait. Just because the river in Taz is 200m above sea level doesn't mean the water will drop 200m to Melbourne. The curvature of the earth would balance it out at some point.
(Arsenio) Hall and (Warren) Oates, no it won't. The curvature of the earth is an gravitational equipotential surface - that is, a line drawn at a constant altitude (measured from sea level) is "flat", so far as water is concerned.
Think about it: if that weren't true, you could achieve orbit by heading down I-35 in Oklahoma, and just driving until you passed the clouds straight ahead.
posted by IAmBroom at 8:30 PM on April 16, 2010
(Arsenio) Hall and (Warren) Oates, no it won't. The curvature of the earth is an gravitational equipotential surface - that is, a line drawn at a constant altitude (measured from sea level) is "flat", so far as water is concerned.
Think about it: if that weren't true, you could achieve orbit by heading down I-35 in Oklahoma, and just driving until you passed the clouds straight ahead.
posted by IAmBroom at 8:30 PM on April 16, 2010
flabdabalet, the wind power purchases will be straight from the market, they are not building any special wind farm for this. And they will be managed by the plant operator. The amount consumed is orders of magnitude below installed capacity.
posted by wilful at 5:54 PM on April 18, 2010
posted by wilful at 5:54 PM on April 18, 2010
Right. So if they're not building dedicated wind farm capacity to power the desal plant, then the net effect of sucking up 100MW of wind power with it is a 100MW reduction in the amount of installed renewable energy capacity for the rest of the state. Some offset.
posted by flabdablet at 4:28 PM on April 19, 2010
posted by flabdablet at 4:28 PM on April 19, 2010
On the other hand, this is a really good use for wind energy. A lot of critics say that the variability of wind energy makes it unsuitable for base loads, but I bet that the water station can be designed with reservoirs to cope with interrupted power. So if it's designed properly, it will never require carbon-generated electricity.
posted by Joe in Australia at 10:34 PM on April 19, 2010
posted by Joe in Australia at 10:34 PM on April 19, 2010
If I'm right about the way the Brumby Government works, I would be surprised beyond surprise to find that there is any concession to variable power supply factored into the design of its desal boondoggle.
I agree with you that a desal plant, if designed with adequate header reservoirs on the inlet side and oversize pumps feeding those headers, could be built to act as a demand leveller, thereby increasing the amount of wind generation that the rest of the grid would tolerate.
However, this would require two things: (a) an integrated energy and water supply policy, as opposed to a random collection of politically convenient piecemeal projects adopted mainly to get rid of a public perception that this is a "do-nothing" Government (b) a willingness to argue for spending even more on a project whose present cost is already raising eyebrows. So it's not going to happen in Victoria - not with this Government and this desal plant, at any rate.
posted by flabdablet at 11:00 PM on April 19, 2010
I agree with you that a desal plant, if designed with adequate header reservoirs on the inlet side and oversize pumps feeding those headers, could be built to act as a demand leveller, thereby increasing the amount of wind generation that the rest of the grid would tolerate.
However, this would require two things: (a) an integrated energy and water supply policy, as opposed to a random collection of politically convenient piecemeal projects adopted mainly to get rid of a public perception that this is a "do-nothing" Government (b) a willingness to argue for spending even more on a project whose present cost is already raising eyebrows. So it's not going to happen in Victoria - not with this Government and this desal plant, at any rate.
posted by flabdablet at 11:00 PM on April 19, 2010
« Older People who died in 2010; early projections | I would pick it out if I saw it and throw it on... Newer »
This thread has been archived and is closed to new comments
(Also, he doesn't address another option: Not building your city in a desert.)
posted by DU at 5:30 AM on April 14, 2010