The middle of Australia is below sea level, I'm not exactly sure how far but It used to be an inland sea. It would be great to make it a sea again. Think of all the benifets, no more useless desert, tourisim, fishing, it would make the air over central Australia more humid totally changing the climate and turn all that barren wasteland into lush tropical rainforest. Instead of being some hell hole that cars frequently decide to break down in the middle of it would be pastures and forest. Another benifet is that it would buy all those small island nations worried about their countries dissapearing under the ocean because of global warming some time by lowering the sea level a little bit. The way this could be acchieved is a massive canal built in from the Great Australian bight to where the land reaches sea level again and from then it would be like undamming a lagoon on the beach, all the water would just cascade into the space and create a beautiful warm shallow sea in the middle of the desert.-- Gulherme, Jun 02 2003 Red Sea | Dead Sea http://www.mfa.gov....fa/go.asp?MFAH0mn70 [Shz, Oct 04 2004, last modified Oct 06 2004] Lake Death Valley http://www.halfbake...ke_20Death_20ValleySmaller, with an in line gravity-powered desalinator. [bungston, Oct 04 2004, last modified Oct 05 2004] Diseases spread by dust storms from deserts http://www.sciam.co...E1-A2D1809EC5880000 [DrCurry, Oct 04 2004, last modified Oct 06 2004] (???) Kariba Dam http://afronet.org....nitor127/report.htm...turned a nasty, disease-ridden stretch of the Zambezi into a wide lake that has revitalized the whole blighted area. Positives and negatives noted in this overview. Of course, they started with a river, not available in most desert areas. [DrCurry, Oct 04 2004, last modified Oct 05 2004] Travel info http://www.smh.com..../1085641702528.html'Australian Sea' holiday for the adventurous [ConsulFlaminicus, Oct 04 2004, last modified Oct 06 2004] SOLAR PUMP solar_20pumpthe way to get the water there !!! [peter2, Dec 26 2009] Land below sea level http://geology.com/below-sea-level/ [ldischler, Dec 28 2009] Land from salt Salt_20of_20the_20Earthwhat to do with all that salt [Loris, Apr 08 2010, last modified Dec 09 2010] Australian Inland Sea II Australian_20Inland_20Sea_20IIanother way [BunsenHoneydew, Oct 21 2010] Torrens/Eyre lake system to Spencer Gulf http://maps.google....440651,7.091675&z=8Google map [BunsenHoneydew, Oct 31 2010] Could you turn Death Valley, USA into an inland sea? http://what-if.xkcd.com/152/ [hippo, Oct 28 2016] Cross Florida Barge Canal https://en.wikipedi...Florida_Barge_CanalProposed 170km (107mi); 28% built; cancelled on environmental grounds. [BunsenHoneydew, Nov 04 2016] Gulf Intracoastal Waterway https://en.wikipedi...tracoastal_Waterway1,690 km (1,050 mi) from Florida to Texas. Partly natural, with locks. Minimum depth 3.7m (12ft). Completed 1949. [BunsenHoneydew, Nov 04 2016] Houston Ship Channel https://en.wikipedi...ouston_Ship_ChannelPart of GIW (above). Partly made of natural channels which have been widened and deepened. 80 km (50mi) x 160m (530ft) x 14m (45ft) [BunsenHoneydew, Nov 04 2016] Saint Lawrence Seaway https://en.wikipedi...int_Lawrence_SeawayFrom Atlantic Ocean through the Great Lakes to Lake Superior. Comparable length to the proposed Lake Eyre channel at 600km (370mi) though much of that is natural waterways, with some dredging. Minimum cross-section (at locks) is 24.4m (80ft) x 9.14m (30ft). Many locks. Eyeballing the map at link it looks like ~10% is canal. [BunsenHoneydew, Nov 04 2016] Stad Ship Tunnel https://en.wikipedi...ki/Stad_Ship_TunnelProposed, Finland. Just over a mile long but 45m (148ft) x 36m (118ft), water depth 12m, to handle ships up to 16,000 long tons [BunsenHoneydew, Nov 04 2016] Delaware Aqueduct https://en.wikipedi...i/Delaware_AqueductWorld's longest tunnel. 137km (85mi) x 4.1m (13.5ft) wide. Completed 1949. Discharges ~2.45m m3 / day or 28m3/s. [BunsenHoneydew, Nov 04 2016] World's longest tunnels https://en.wikipedi...unnels_in_the_world [BunsenHoneydew, Nov 04 2016] Dahuofang Water Tunnel https://en.wikipedi...uofang_Water_TunnelWater supply tunnel for seven Chinese cities. 85km (53mi) x 8m (27ft) diameter. 2.5 years at about US$750 million [BunsenHoneydew, Nov 04 2016] Mississippi River Gulf Outlet Canal https://en.wikipedi...93Gulf_Outlet_Canalper anno [BunsenHoneydew, Nov 04 2016] Tennessee-Tombigbee Waterway https://en.wikipedi...3Tombigbee_WaterwayPopularly known as the Tenn-Tom. 377km length, locks are 2.7m deep and 33.5m wide. 10 locks and dams, and one deep cutting - the Divide Cut: 47km x 53m deep. Completed in 1984 for a mere US$2bn ($4.65bn in 2016) [BunsenHoneydew, Nov 04 2016] 1830 map of Australia, showing large inland sea https://www.theguar...g-in-pictures#img-7 [hippo, Nov 16 2016] I like this idea. I'm off to get some nice beach front acreage out near the Alice. Bun.-- briandamage, Jun 02 2003 Hmmm... Conceptually baked. Will search for link.-- Shz, Jun 02 2003 <link>-- Shz, Jun 02 2003 At least with this plan we don't have to move icebergs, like in that Sahara Ocean idea a while back.-- snarfyguy, Jun 03 2003 I'll give 'ya a croissant if you chain Kylie Minogue down first and then let the water flow.-- goober, Jun 03 2003 C'mon! no offense, but this can't be an idea. It's a WIBNI. Still, if you chain both Kylie and Nicole to the bottom, I'll help you see how we can make this work.-- Pericles, Jun 03 2003 Same idea as Lake Death Valley (link), except bigger, and not freshwater.-- bungston, Jun 03 2003 All the salt should solve the slug problem in central Australia at least.-- Gulherme, Jun 03 2003 It urns out that creating inland seas is a good idea for more reasons than giving the locals a swimming hole: diseases are spread by dust storms arising in deserts. Alarmingly, the last foot and mouth outbreak in Britain (the one that shut down the countryside for many months) evidently came from the Sahara.
(See link.)-- DrCurry, Jun 20 2003 Wouldn't they tend to be more incubated in humid climates, though?-- RayfordSteele, Jun 20 2003 The Menzies government of the 1950s actually did a feasibility study of this very idea. The proposal was to use nuclear charges to dig a canal from Spencer Gulf near Port Augusta to Lake Eyre.
I have mixed feelings about this project. I have an instinctive mistrust of enormous bioengineering projects, because of the history of destruction other grand-scale projects have left in their path. cf Aswan Dam, Three Gorges Dam, Narmada Valley Dam. There would be problems with salt and no doubt the extinction of many delicately poised arid land ecosystems.
On the other hand, the creation of a permanent inland sea would probably have many of the effects Gulherme suggests, creating rainfall across the inland, and opening many extremely arid areas to agriculture and tourism.
Forget about it being a solution to ocean rising from global warming - the volume of water involved would be miniscule compared to the total volume of the world's oceans.
So neither bun nor bone from me...-- BunsenHoneydew, Jun 21 2003 Would it not be possible to create agricultural land by this means? Rice can grow with fairly salty water, and edible sea-weed...-- git, Jun 22 2003 First, this sort of massive geo-engineering is a great thing to contemplate. It may be decades away from implementation, but fun to consider.
Second, I think the canal idea won't work. The atlases I've checked seem to indicate that the length of the dig for the Lake Eyre canal would be over 100 miles (4 plus times that of Suez and Panama. Second, in considering the route of lowest elevation, I think there are heights of 200 feet plus that would have to be dug through. That's way more than in Panama and Suez. In other words, for each square foot of dirt moved for Suez, and maybe for each five in Panama, I think you would have to move something like 100 square feet of Aussie dirt. Not very practical with such modest economic benefits in the offing.
So, how about a pipeline? Somebody mentioned 6 meters as a diameter, but that seems excessive in both cost and need. How about somewhere between 1 and 2 meters in diameter? How would it work? Like a massive garden hose, one end several meters deep in the ocean, the midsection snaking over hill and dale, and t'other end several meters below sea level in southern Lake Eyre. You'd have to fill it with water to get the syphon action going, and that'd mean hundreds of truck loads trucked to a sealable opening at the highest point in the pipeline. Also, you'd have to have valves closed at both ends during the fill. Open the ocean end, then the lake end, and watch it gush forth. The lowest point in Lake Eyre seems to be some 31-32 feet below sea level, and conveniently located about as close to the ocean as you can get within the lake. If the pipeline's outlet were to be situated at this lowest point, (and assuming a current level of 10 feet) you'd have some 20 feet difference in elevation powering the syphon action.
To what end? I say who cares about the increase in salt? Why even think about desalination? I say the real benefit would be the massive increase in the lake's surface area bringing increased local evaporation which would bring more rainfall. Central Australia is severely parched, and even a modest increase in rainfall would bring major economic benefits. The current population of the entire Lake Eyre watershed (which looks to be the size of Texas) is an astonishingly small 50,000. And I assume that the population currently residing below sea level along the edges of the current salty lake is zero or nearly so. (The level of the lake rises and falls year by year, depending on rainfall. So there is no defined shore line on which to establish a baitshop/boat rental business.) And this brings up a minor benefit of the pipeline. By providing more siphoning draw during low rainfall periods, it would help to stabilize the shoreline, and thus promote such business-based settlement and accompanying tourism.
Re hydropower, forget it. You've got a fall of some 20 feet, and the drag of the pipeline to slow even that modest fall. After the lake level is only 10 feet below sealevel, then you've got a fall of ten feet. Hydro? Fugetaboutit!
Decreasing the worldwide sea levels? Again, forget it. I doubt the sea level would fall more than a fraction of an inch. The lake area and capacity, as envisioned, is miniscule compared to the world's oceans!
Re concerns over the salt and the great bugaboo "environmental degradation," look at the Caspian Sea. It's below sea level, has dropping levels and rising salt levels. But its problems are related to the massive population (and its unregulated pollution) that lives along its shores and inlet rivers. Even lightly populated Australia will evenually need increases in liveable land. I say it's time now, before you've got a million or so people mucking up the process, to re-engineer the arid interior.-- ertdfgcvb, Aug 18 2003 Nice thinking.-- bristolz, Aug 18 2003 It is illegal and immoral to destroy Aboriginal sacred sites, which this idea would certainly.-- BillyBoy, Nov 04 2003 I like this idea, and also [ertdfgcvb]'s pipeline suggestion. I would never want it to get further than halfbaked though.
[ertdfgcvb] - // You'd have to fill it with water to get the syphon action going, and that'd mean hundreds of truck loads trucked to a sealable opening at the highest point in the pipeline //
Instead of the trucks, why not pump water in at the sea end? Put a temporary 20m high vertical pipe at the desert end until the pipeline's full.-- benjamin, Nov 04 2003 This is a terrible idea. Not only will it bring more salt to the area (as UB mentioned) it will tottaly stuff around what is already a beautiful place. Why would you want a rainforest when you can have red kangaroos jumping around. You really are a moron gulherme. Why don't you get back to your france adventure instead of waisting your time here posting stupid ideas.-- Mind_Boggle, Nov 05 2003 It is a great idea except for the unknown side effects.
With enough water in the red centre evaporation would lead to cloud formation which would lead to rain which would allow vegetation to florish.
Once vegetation got established the meteorlogical systems would change and maybe at some point the almost permanent high pressure area over Australia would weaken or even move, when that happened moist air would move in from the Indian ocean to fall as rain in the red centre.
Eventually an Amazonian climate would be established with a net flow of water out to sea. Before that would happen however a very large portion of central Australia would be under water for part of the year. Once established however the Amazonian climate pattern would flush all the salt back out to sea and all inland water would be fresh again.
Water from this system would also perculate down to replenish the continental aquifier.
Yes, I know the Amazonian climate is effected by the Andes of which there is no equivalent in Australia. Maybe the Australians could just build a big wall down the left hand side? They are pretty good at doing big job, worlds longest fences etc.
There are some serious side effects to consider not the least of which is what the country would be like for the 100 or so years that it would take the system to stabilise and the effect moving that permament high pressure area would have on the climate of both the rest of Australia and neighbouring countires.-- KiwiJohn, Dec 03 2003 Apart from the engineering, social and environmental issues the idea raises, one wold need to consider what would happen once it filled - Australia would fold up like a damp chapatti and sink below the southern ocean, would no longer impact on the roaring forties and South America would get blown across the Atlantic into Africa, the earth would develop a speed wobble and go really pearshaped adn gravity would be unreliable. I don't think it is a good idea really, on balance-- Okapi, Jan 19 2004 //Australia would fold up like a damp chapatti and sink below the southern ocean// Only in the dreams of the righteous, Okapi.-- DrBob, Jan 20 2004 I think that instead of a canal being excavated to the lake, it would be better to dig a tunnel from the deepest part of the lake to the continental shelf. This would allow the salt to be purged as soon as there is an inflow into the lake. It would also prevent sediment to choke the Spencer gulf by depositing it into deep water of off the coast. The syphon system would not work because the lake would fill with salt very quickly. I don't know how quickly the tunnel could be built, but modern TBM's such as those used on the channel tunnel could be used. The wetter climate would allow massive forests to be planted(carbon credits) and agriculture to be increased. This may have to be done to slow the greenhouse effect.-- adon, Jan 28 2004 I don't want to have to use a hovercraft if I want to drive from here to the Eastern States.-- Detly, Jan 29 2004 remember the dams in china? I don't remember the precise details, but apparently a shift of that much water was gonna throw off tthe balance of the earth's orbit. I don't know if it did, will, or isn't gonna, but I'm pretty sure that if there is an effect, moving a small sea inland would have one even more drastic. I could be wrong. neutral-- schematics, May 11 2004 Oh, come on. Throw off the Earth's orbit?-- bristolz, May 11 2004 Hey I just said I wasn't sure. But it does kinda make sense. Spin a top. now, sever a side of it and glue it back on a milimetre or so away. it's not gonna spin the same way.-- schematics, May 11 2004 Earth's mass, say 6 x 10 to power 24 kg.
If inland sea covered say 2 million square kilometers with an average depth of 50 metres, mass of water would be 1 x 10 to power 17 kg approx.
So, 0.0000016% (1/60,000,000)
Analogy: If you weigh 100kg, would a 1.6 milligram speck of dust cause you to wobble as you walked down the street?-- ConsulFlaminicus, May 12 2004 guess not.
What about the chaos theory? An autralian sea could cause me to burn my toast-- schematics, May 12 2004 The reason this idea is considered halfbaked is because only half the idea has been discussed.
Some new points to consider:
1. The MAIN effect of an inland sea is evaporation that will cool central Australia a fraction more than it is now. There will be no rainforests, no substantial agriculture, no fishing and little local rainfall. It is just too hot in central Australia for these to occur and most evaporation will rise rapidly and disperse without causing rain. The cooling is he KEY to real benefits. Much of the rainfall in the eastern states comes from rain bearing fronts that move in an easterly direction across Australia from the Bight and the west coast. These occur infrequently due to the intense heat in central Australia which quickly vaporises any precipitation. Most of these fronts are thus forced along the south coast of Australia and into the Tasman sea. A slight change in this current dynamic by flooding Lake Eyre, will increase the frequency of precipitation entering the continent and crossing the gauntlet to the eastern states. Based on agricultural improvements when the lake is flooded every seven years or so and on declines in agri output during severe drought, I estimate that on average, a Lake Eyre inland sea will add $3 billion per annum to the agri economies in the eastern states. It will also subsequently save additional millions by reducing drought associated bushfire events.
2. The least expensive method of creating a canal from Spencer's Gulf is to use the Suez DREDGE canal technique, with some piping at intractable zones at the top end of the Flinder's range. This will work well because there is an existing silted channel from when the lake was last connected to the ocean. I estimate that Dredging for most of the 300 Km required will cost around $1 million per Km. The overall cost would be about $800 million comprising $300m for dredging, $100m for necessary piping, $200m for a control dam at the head of the Gulf, $100m for treatment and monitoring works at the lake entrance and $100m for crucial vegetation around the entire shorline.
3. The shorline revegetation is crucial to the sustainability of the lake. It would be no more than a Km wide with a 4 tier structure: salt marshes, wattle foragers, casuarinas/river oaks, eucalypts and salt bush. The vegetation will add to the inland cooling effect, absorb some salt from the lake, create habitat for wildlife and create a pleasant vista for tourism.
4. The project will add about 8 inches of salt per annum to the lake. This gives the project a 50 year lifespan or $150 billion dollar revenues before it becomes non viable. Within 30 years of project commencement, some of the $benefits would have to be chanelled into research and development of salt removal technology. Some possibilities are: selection of aggressive halophytes (salt plants), A brine return channel to the Gulf, optimisation of saltwater inflows to maximise rainfall, development of the Cooper river inflow catchment from Queensland to flush the lake more regularly with fresh water, taking advantage of increased natural fresh water inflows when available, salt processing industries and researching the use of salt as a slurry for manufacturing building materials for local use.
5. Before committing to the project, research its economic and ecological effects by developing inflow catchments like the Cooper, so that the Lake will flood more predictably and regularly. This will involve some sacrifices in Queensland for some time while the project is assessed. As a national strategy and for confirming future benefits to Queensland from the project, this should be agreeable to all stakeholders.
There are several more important considerations. It is best at this point however to get some feedback before continuing.-- fredjmoore2, May 29 2004 Some additional information on Lake Eyre:
1. The following link is an Austarlian Government site detailing current Lake Eyre issues.
http://www.deh.gov.au/water/basins/lake-eyre/
2. The concern about percolation of salt into the water table is unfounded for 2 reasons.
A) As a lake bed that is many 10's of thousands of years old, Lake Eyre has built up layers of very fine silts and clays which block any percolation of salt water into the water table. B) The lake is built on dense salt formations which dissolve when the lake is flooded every 7 years or so. There is no pecolation of salt into the water table during these events.-- fredjmoore2, May 29 2004 Fred,
Add to your equations the cost of the largest geological survey ever undertaken - you'll need that to be sure there are no physical containment problems with the new sea (many parts of Central and Southern Australia have extensive cave and sinkhole structures) - and the cost of purchasing extensive tracts of private land.
If we accept your figure of //eight inches of salt per annum// and thus a //50 year life span// for the 'project', why the hell would we want to do it if the duration of the climatic benefit is so short term? After 50 years, what's the situation? 800 gazillion tonnes of salt sitting in the middle of Oz, causing who knows what climate effects through reflection, and periodically getting flushed down into the Southern Ocean in a great mass of poisonous alkalinity.-- ConsulFlaminicus, May 31 2004 Once the Lake Eyre basin is filled to the brim with salt, where will the semi-annual floodwaters go?
A tunnel which sloped towards the ocean rather than towards the lake should pretty effectively flush the salt content. The extra expense would pay off in the permanence of the result, as opposed to the projected 50 year life span of the cheaper options. Unless of course the tunnel starts to plaque up like a sclerotic artery.
I'm not sure the objection about caves and sinkholes is much of a worry - there's plenty of water in the Southen Ocean to fill them up. With luck, surveying would reveal some existing voids which could be exploited as part of the tunnel.-- BunsenHoneydew, Jun 03 2004 "Keep your filthy hands off my beautiful desert" Mucking about with Mother, on this scale, has always turned out to be a bad idea; usually for reasons that were not imagined in advance. It is dry and it should stay that way. Bone.-- James Newton, Jun 18 2004 Aussie Friends:
How about a sea-level barge canal from Port Augusta through Lake Torrens to Lake Eyre? This would in effect create a shallow "Eyre Bay", which would moderate the harsh climate of South Australia and end the dust storms of the dry lakebeds. However, it would not create "an Amazonian climate" in the area as someone else suggested -- the area below sea level is too small and too shallow for that.
Salt Buildup? A sea level canal would mean saline levels would equalize more or less, with periodic heavy rains flushing out excess salt to the Indian Ocean.
Cost? As others have pointed out, a deep water ship channel would be prohibitive, given the distance. However, a shallow barge canal would not. For a good idea of what it might cost, see the American Tennessee-Tombigbee ("Tenn-Tom") barge canal project, which also is about 200 miles: www.tenntom.org More digging would be required for an Eyre Bay canal, but no ship locks would be required, unlike Tenn-Tom.
Such a canal would be a boon to the mining and freight hauling industries, and would bring life to an economically deprived backwater (no pun intended), just as Tenn-Tom brought economic life to the backwoods of Tennessee and Alabama in the USA. The Port of Adelaide could act as the Port of Mobile does for Tenn-Tom, a place where the goods move from barge to deep water ship. A barge port for Oodnadatta, anyone?
Of course, now that Lake Eyre is a National Park, the whole thing may be moot. But I'm just a bloody Yank (or Johnny Reb, as the Tenn-Tom case may be), so it's up to you fine people.-- NickB, Nov 29 2004 I read this idea to one of my students and he replied: 'what if the whole thing sinks. where are England gonna poach cricketers from then?' hee hee.-- etherman, Nov 29 2004 <sigh>
[NickB] Some quick calculations.
Volume of lake Eyre when full is 34cubic km, or 34 million megaliters.
Evaporation in the area approximates 1.5m per year - over the approx 10,000km square surface area of the lake, that's about 15 million megaliters.
Assume your 'barge canal' is about 50 metres wide and 4 metres deep - gives cross section area of 200 square meters.
A quite rapid flow rate, from the sea ,through the canal, of 2.88 kilometers per hour, or 0.8 meters per second would thus take 100 years to fill the Lake Eyre basin (ignoring evaporation)
To fill the basin over ten years, while compensating for evaporation, would take 184 million megaliters of flow - that means the water in your canal travelling at 156 kph, or 43 meters per second, or 260558.339298 furlongs per fortnight....
...and don't get me started on the salt loads again....-- ConsulFlaminicus, Nov 30 2004 ...can't....help....myself.... uunnngggh....
Sea water has about 35 grams of salt per liter.
The amount of salt left behind in the Lake Eyre basin every year, if Lake Eyre was to be filled with sea water and based on the evaporation data above, would be about 525 million tons.
If there was no flushing event for 30 years (which seems to have happened frequently in the past few centuries), there would be no room left for any water, and 15.7 billion tons of salt baking in the sun.
if there was a flushing event after several years of escalating salt concentration, the ecological disaster in the Spencer Gulf would be severe.-- ConsulFlaminicus, Nov 30 2004 So, anyone want to buy a central Australian salt mine? Seems to be the one thing we're certain to produce...
This idea is feasible, but just because it can be done doesn't mean that it should be. It would have too great an impact on, well, central Australia, and would leave our descendants cursing us for centuries.-- david_scothern, Nov 30 2004 Actually, all that salt could be useful. The Dead Sea is mined for salt - Australia could do the same.-- Loris, Nov 21 2005 Can I still dig for opals, and hang out at the Pink Roadhouse in Oodnadatta?-- sleeka, Nov 21 2005 I think that this idea is definitely worth carrying through; particularly with the begining of global warming and Australia's worsening drought conditions.
Re; environmental issues, the 'delicately poised' eco-systems are just that because they are in a perilous environment with little of anything left to sustain it!
Why care if an inland sea is more salty? It already is DRY and salty out there. It may turn out to be only fractionally saltier depending on the volume of water that could be contained there. A channel or tunnel could take advantage of high ocean tides and close during low tides.
Spreading the water surface on the earth could aid, in some small way, cooling of the earth's temperatures. As mentioned by other contributors here, precipitation will produce rain, which will deposit fresh water in other areas and increase vegetation and animal life. Maybe one day we might see large green areas on satelight maps where there had been desert for the last 50,000 years.-- Castle, Oct 17 2006 Flaminicus, can you help me with the following thought experiment?
I'm imagining the canal getting blocked by salt as the sun evaporates the 'water' part of salt water. I'm imagining following the canal from the ocean end until the blockage is reached. Now I'm trying to imagine what is happening in that last little bit of salt water as it laps against the accumulated salt sludge.
This last little bit of water surely has a very high salt content, higher than the water in the ocean. Won't there be a tendency for that dissolved salt to move down the concentration gradient into the ocean? <tries to remember about osmosis from many years ago>
Then, won't the salt sludge tend to be eroded over time, and the blockage cleared?-- pertinax, Oct 18 2006 The answer to the salt problem is to incorporate the Bradfield Scheme in conjunction with the canal/pipeline project. (Google this). A continuous body of water from the Upper Herbert river in North Queensland to the Spencer Gulf. A delta could be created in the Cooper Basin.-- saferain, Nov 04 2006 I don't think that filling up the Lake Eyre with salt water is a good solution because it will add salt to the entire area. However, thanks to its below sea level elevation, The Lake Eyre basin would be an ideal place to transfer desalinated seawater from the Great Australian bight (via a pipeline) without the need of additional pumping power. When you think that Spain and Israel are curently using desalinated seawater to irrigate their semi-desertic land, one can presume that there is an economical interest to do so! (cost of desalinated water is the double compared to traditional water sources). However, new irrigation technologies are very efficient and they can grow almost anything using a fraction of the water that would be required with traditional techniques. Desalination should only use clean and renewable energies like the new desalination plant in Perth. Priority should be given to grow (fruit) trees, which have multiple benefits, capture Co2, absorb the heat, protection against sand storms, and production of nice oranges!-- Bracam68, Dec 18 2006 i think it'd be a waste of energy and money to desalinate the interior of australia, why not pipe desalinated water from the coast to municipal water supply lines and use waste heat recovery water from air - renewable free desalinated pre-filtered freshwater. then from there you just fill up the reserves and tanks and build out pipelines in series and parallel as inland as you need. 80% cost savings on current state of the art desalination.-- costellogroup, Jul 14 2007 see the link see the mechanism here, for transporting the water. Perhaps salt, so chemically volatile, can be used by some mechanism to aid the process. Failing that, the fish and chip mega store.-- peter2, Dec 26 2009 If you just wait fifty thousand millenia or so, the Gulf of Carpentaria will become a lake when Australia collides with Indochina.-- nineteenthly, Dec 26 2009 Guys, can we hurry a little? If we're going to flood a large part of Australia (which sounds, on gut feeling, a good idea), we really ought to do it before Ubie gets back.-- MaxwellBuchanan, Dec 26 2009 Excellent idea, and you don't need a massive canal, you could start off with a very narrow and deep one, the flowing water stream would make it wider.-- Inyuki, Dec 27 2009 [MB], i don't think he's likely to be in the middle because it's pretty empty. The probability that he lives somewhere in the middle is small because it looks like most people live around the edge.-- nineteenthly, Dec 27 2009 the salinity question IS important. All inland bodies of water fed from salty sources have increasing salinity and it eventually makes them very barren. The buildup of salt also slows evaporation and can cause the soil porosity to decline gradually raising the water level. Wells within a significant area around the "inland sea" will become brackish and be useless for agriculture. see Utah.-- WcW, Dec 27 2009 //All inland bodies of water fed from salty sources have increasing salinity//
Wait a minute. Aren't *all* inland bodies of water ultimately fed from salty sources (i.e., the sea) via the normal water cycle?
Isn't central Australia already notoriously saline, despite being far from the sea?
Wouldn't the presence of an inlet of the ocean make it possible for some of the existing salinity to get flushed into that ocean by the occasional rainfalls where, at present, the rain just evaporates because it gets a chance to flush any salt?-- pertinax, Dec 27 2009 Any body of water that is FED by a salty body of water and LOOSES most of its water to evaporation will gain salinity. It's simple to see that any body of water that gains salt water from the sea and looses it to the air (a dessert) would gain salinity continuously until it was saturated with salt. It seems clear to me that any such project would be identical to building a huge salt production pond.-- WcW, Dec 28 2009 //see Utah// Ummm... not so sure we're a good example of what you're trying to say. Our local salt pond is fed from numerous sources - all of them fresh water.
Our buildup of salt dates from the time Lake Bonneville *lost* its connection to the ocean.-- lurch, Dec 28 2009 There's an estuary somewhere in Australia whose water is more saline than the adjoining ocean because the land near it is so hot and arid. The same seems to have been true of the Tethys in Triassic times.-- nineteenthly, Dec 28 2009 //huge salt production pond//
Ponds aren't connected to the ocean. Why would the salt not travel down the concentration gradient?-- pertinax, Dec 28 2009 Have we got to dessert yet?-- pertinax, Dec 28 2009 so affirming my basic point that if a body of water constantly looses water to the air and is not refreshed with fresh water or allowed to equilabrate with the ocean the result is very salty even if the feed water is fresh. Salt production "pond" is the correct industry terminology.-- WcW, Dec 28 2009 I think you're both right... well actually both wrong.
pertinax, in a closed system you'd be right - the salt would diffuse down the concentration gradient until equalibrium was reached with all the water being equally salty. However, in this case the system isn't closed - the sun is baking off water in the inland sea.Under typical condtions there would be a net influx of salt. Water flow would be more than enough to counteract diffusion until the whole thing had salted up - if it were supplied by an open channel, probably some distance along that.
However, WcW, he's right that this isn't necessarily equivalent to a salt production pond. If there is occasional, massive flooding, then this could periodically wash salt back out to sea. The water could come in, be reduced in volume to become extra-salty, then flushed back out when the inland area floods. Freshwater being lighter than salty, it would float on top. However, this may not be sufficient to remove all the salt accumulated in the interim - my impression (without having done any sums) is that it's not anywhere near enough.
As I said above (a few years back) mining the salt would be straightforward. Do this enough and there's no significant salt buildup. Water arrives at one end of the 'sea', gets gradually saltier across the lake, and the salt is extracted in evaporation ponds on the other side. The area surrounding the lake would benefit from increased rainfall, and the edges of the new lake become highly desirable for living, tourism etc.
Alternatively, one could consider attempting to flush the system. If the difference between high tide and low tide is enough, one could use two pipes, at either end of the inland sea and well separated at the coast. At high tide seawater would be permitted to enter along one channel (perhaps using a weir), and at low tide to exit the system via the other (perhaps using some active system).-- Loris, Jan 03 2010 while you can keep the water salinity near tonic to the sea by washing it out occasionally the surrounding land is another mater. Without the desalinating action of rain the soils in the floodplain will become salty. Not to mention the groundwater contamination issues. I would think that any new fresh water would take a long time to "resolve" (vegitation, rainfall, new aquifers) thousands of years I suspect.-- WcW, Jan 04 2010 //... Without the desalinating action of rain the soils in the floodplain will become salty. Not to mention the groundwater contamination issues. I would think that any new fresh water would take a long time to "resolve" (vegitation, rainfall, new aquifers) thousands of years I suspect.//
The floodplain itself is presumably already rather salty. Salt gets washed in and then has nowhere to go. fredjmoore2 mentions this above - and also that little groundwater seepage occurs due to its long previous existence as a floodplain. Unfortunately the link he gives is no longer valid; not even the Wayback machine remembers.
However, this assurance does not apply to any canal dug to (or from) the area. It would probably be a good idea to line them to prevent salt contamination of the neighbouring land. That should be relatively straightforward I'd have thought - compared to the trouble of digging the canal in the first place.
I don't know what you mean about fresh-water resolving.-- Loris, Jan 04 2010 This is going to be a lot bigger than Suez if you want a channel that flows both ways with the tide and can exceed the rate of evaporation. What is the goal? Given adequate size the inland ocean could change the entire climate of Australia and possibly the world (at least NZ) and to what end? I'm not confident that you end up with more fresh water and that is the real limiting factor re. the Aussie population.-- WcW, Jan 04 2010 I think it would have to be two channels, each one-way - if you want to avoid salt build-up. Although if the salt is used for industry you'd only need one. Having two would mean there'd be a nice low-energy transport system both in and out - and one could still pan salt on a smaller scale if the lake was segmented.
Neither channel would have to be as large (in cross-section) as the Suez canal. Of course the channel flowing into the continent would be the larger.
Changing the climate of central Australia is a big part of the point. The area of the lake wouldn't be all that enormous, though, so it probably wouldn't be enough to change all of Australia's climate.
I personally wouldn't like this sort of idea to go ahead without full consideration of the real cost : what species would be lost? It may be that there wouldn't be much of a down-side; if the whole of central Australia is relatively homogeneous desert then maybe only a manageable percentage of this would be changed with little loss of diversity. There may be benefits to other wildlife (as well as the human benefit). On the other hand, maybe a unique habitat stuffed with interesting creatures would be washed away. The images I've seen of the area don't suggest that though - it basically looks totally dead.-- Loris, Jan 04 2010 Something I haven't seen commented on is the wind patterns and surrounding mountains. The evaporating water doesn't just cease to exist. There will be water vapor in the air, and the wind will blow it somewhere, and it'll turn into rain.
Where will it get to? Will a good fraction of it get trapped inside the same watershed? Would there be a worthwhile amount falling into areas such as the Australian east coast?-- lurch, Jan 04 2010 I'm surprised to see you say that, lurch - I thought we'd all been talking about it. While maybe no-one has said it explicitly, I at least have been assuming that a decent proportion of the water would fall as rain in the same watershed.-- Loris, Jan 05 2010 Is central Australia above or below sea level? Would a channel running right across the island work, or would water simply pool it?
Cutting Australia in half with channels, although only by 10m or so, would work.-- Selky, Jan 17 2010 See link for solar pump. to get the water there. I'm dubious that the miniscule height gradient being enough for a gravity or siphon feed. The net salt increase is a big problem. And many say the hoped for precipitation would be far too random. Considering the surrounding heat, the lack of nearby terrain to induce the dynamics for precipitation...what goes up may may well come down .... in new zealand. Are there any ways of prototyping this? Studies of the effects of the filled lake are possible now with Lake Eyre about to get some water presently. And after all, this data is already recorded.(somewhere). There would definitely be significant Aboriginal Sacred Sites in the area. The wildlife is also significant. Is it more significant than this project? Is it possible to meet requirements for Indigenous, wildlife, salinity and cost parameters? We need to do something. Unforseens may include benefits as well as problems. Agriculture need not be confined to freshwater types. A group called enersalt i s working on energy generated from salt ponds. We need to move on this.-- peter2, Apr 05 2010 //There's an estuary somewhere in Australia whose water is more saline than the adjoining ocean//
You might be referring to Shark Bay, [19thly], except that I don't think it's an estuary.-- pertinax, Apr 06 2010 Sounds like there'll be a lot of water flowing in and out of this inland sea as a result of the tides. The canal/pipe/siphon/whatever connecting it to the ocean will probably erode quite quickly.
On the other hand, it would make an excellent place to put a turbine and generate some power.-- Wrongfellow, Apr 06 2010 All hail Google Calculator and Wikipedia.
[ConsulFlaminicus]'s calculations of Nov 30 2004 leave out two very important figures. One is the natural inflow of fresh water from the catchment, which fills the lake every seven years. He also completes his calculations // (ignoring evaporation) // ... which, well, we can't really - if we could ignore evaporation, the Lake would already be full! Evaporation is kind of the main deal.
So, a different approach to the calculations. Start with a full lake after a flood event, and try to keep it full. What we have to do then is bring in enough seawater to match the evaporation rate.
Let's take his figure of 15 teralitres of annual evaporation. Thus we need an inflow of
15 000 000 000 000 / 365.25 / 24 / 60 / 60 = 475 321
So let's say half a megalitre per second. That seems ... significant, but doable. For visual reference, 1 megalitre = 1000 cubic meters, or a cube of water 10 meters (~10 yards) to a side. Or if you prefer, there's 2.5 of them in an Olympic size pool.
Let's take that proposed barge canal (200 sqm cross section) and run the water at 1 m/s (3.6km/h or 2.2mi/h)
200sqm x 1 m/s = 200 000 litres / second
Or just under half what we need. So, a canal with a 500sqm cross section - say 50 meters wide x 10 deep - should do it. Or a circular pipe or tunnel 25 meters across. Again, big, but doable. Or, we allow the water to flow at 2.5m/s (9km/h or 5.6mi/h)
(400km x 50m wide canal adds 20 squ km of evaporation area: insignificant)
So that's evaporation taken care of: when the next flood fills the lake, it should stay full for good. On to the salt.
Seawater has 35 grams of NaCL per litre. So we are importing
35 x 15 million megagrams = 525 000 000 tonnes per annum.
Spread that out over the area of the lake and that's:
525 000 000 tonnes /10 000 sq km = 52.5kg /m2 /pa (10lb/ft2/pa)
Density of NaCl = 2.165 g/cm3, so the depth of salt (pretending it all sinks to the bottom as a solid) increases at the rate of
52500g/m2 / 2.165 g/cc = 24249.4226 cc/m = 2.4cm/pa (1in/pa)
Thus a lake with an average depth of 10 meters fills up solid with salt in 1000cm/2.4cm = around 400 years, which is significantly longer than I would have guessed.
If you want to make it permanent however, that salt is going to have to be flushed out to sea, one way or another.
Now, the lake floods naturally with fresh(ish) water every seven(ish) years. Let's assume that's an over-estimate and make it fill to the brim every ten(ish) years. This implies a freshwater inflow of 34/10 = 3.4 million megalitres/pa. If that water picks up enough salt to make itself as brackish as seawater, then it can remove
35 grams x 3 400 000 000 000 = 119 000 000 tonnes/pa
As we're importing 525 000 000 tonnes/pa, that still leaves us with ~406 million tonnes/pa to remove.
AND: freshwater flushing only works if it can reach the sea. If our pipe/canal/tunnel system raises above sea level at any point, we're screwed. Even if we dig a ten meter deep canal dead flat all the way, we may still be semi-boned, and here's why.
Saltier water will sink to the bottom. We'll end up with a pool of dense, cold and intensely saline water at the lowest point of the lake. Inflowing fresh water will probably just glide right over the top of it, without stirring it up at all. Unless we dig and maintain a 20 meter deep channel all the way to the center and bottom of the basin, that brine ain't going nowhere.
On the other hand, this may not be such a big deal. The area below 10 meters depth will perforce be a small fraction of the total Lake's surface area. Even if that area is biologically dead, the 10 meters above it, and all the <10m deep shallows between it and the shore, should have a more tolerable salt concentration and be biologically active. Assuming there is no mixing between the layers.
But let's say that doesn't work, or doesn't work well enough, and that a 20 meter deep channel is out of the question. By one means or another, we need to shift 525 million tonnes of salt per year, on average, out to sea.
525 million tonnes/yr /365.25 /24 /60 /60 = 16.6362461 tonnes/second (18.3387139 short tons/second)
Now that *is* significant. I think we can all agree that ain't going out by truck; even pumping it out as brine or slurry is going to require scads of energy.
So here's my proposal:
Build your fat-enough barge canal at sea level all the way, and a separate and smaller return channel for brine.
The most saline water should sink to the lowest point of the basin. So start a return pipeline there. I'll throw in a wild guess here and say that a concentration of salt four times that of seawater (140 grams/litre) is acceptable down there. Consequently, the return channel can be 1/4 the cross sectional area of the inflow channel, or 1/16th the diameter. That gives us a pipe or tunnel 25/16 = 1.56 meters (just over five feet) across.
Totally doable!
What's more, we have a spare few decades in which to install it before the salinity becomes a problem.
A sealed, overland pipe with an ocean outflow >20 meters below sea level should siphon continuously; the brine at the outflow will be denser than seawater, so it should tend to sink.
Mind you, a pipe requires maintenance - a breach anywhere along its length, creating an air bubble, would halt the flow. So it looks like the truly permanent solution is a tunnel straight through bedrock, emerging >20 meters below sea level. That is, of course, unless the bedrock itself is soluble or reactive in brine (limestone?) - this would cause even more headaches than a pipe.
I've run these figures three times and they seem to hold up. If I've dropped a unit, an order of magnitude or my marbles somewhere please let me know.
I propose we begin at dawn. BYO shovel. [+]-- BunsenHoneydew, Apr 07 2010 Course, if a ~400 year lifespan for the project is acceptable, then all the salt-return-channel brouhaha above is moot.
Now to ponder the effects, every seven years, of 34 teralitres of floodwater turning up in a matter of a few weeks, only to find there's already 34 teralitres in the way.-- BunsenHoneydew, Apr 07 2010 //Course, if a ~400 year lifespan for the project is acceptable, then all the salt-return-channel brouhaha above is moot. //
...And that's why humans should never be allowed to engineer things on a large scale. Something with the potential to affect ecosystems, etc should be planned with an infinite timescale.-- Custardguts, Apr 07 2010 400 years? most projects here in the states have a lifetime of <4 years and the all the foresight of a naked mole rat. considering the results at 400+ years is mind blowing. I still think that the following indefinite period of brackish lifeless pond followed by inhospitable lifeless salt flats might outweigh the 400 years of salty ruined ecological apocalypse.-- WcW, Apr 07 2010 bunsen, you have not considered the idea for a passive solar pumping system. Nor have you followed the Enersalt lead. there is a system to gain power from salt ponds. All that is required is to use that to desalinate the water enroute. discharging the salt etc on the way. WIBNI me if you like. but please edit out your whitespace.-- peter2, Apr 07 2010 The main question is this: if Australia didn't exist, would anyone actually feel the need to invent it?-- MaxwellBuchanan, Apr 07 2010 And if, in inventing it, we would then design it as an incomplete donut enveloping a substantial hole of sea-water. Actually, that sounds great!-- peter2, Apr 07 2010 You know, I think I've got a solution for what to do with all that salt... (link)-- Loris, Apr 08 2010 [peter2]: Your "solar pump" depends on moving parts, and thus on human maintenance even moreso than a pipe or tunnel. It is not "passive" in any sense of the word. And still requires a pipe or tunnel.
There's no reason energy should or could not be extracted by solar ponds ("Enersalt") at any point in the system - the advantage of a closed return pipe to sea is that it should require no energy input at all (pace maintenance), as it gravity syphons.
Whitespace between lines of calculations stays. The point of the calculations is to show that the overall proposal of a permanent "Australian sea" is somewhere within the ballpark of humanly feasible, and that it need not be a silted up disaster area within a generation.
Think long term. Who is going to maintain those pumps for the next thousand years?
Truly, the only "permanent" solution would be to dig a channel from the sea the full depth of the lowest point in the basin, and sloping towards the outlet. That is some monster engineering, but still probably within coo-ee of doable.-- BunsenHoneydew, Apr 09 2010 Do you mean that this within one standard deviation of possible or are you suggesting that it is within shouting distance of possible using the aussie ' Coo-EE ' herding call?-- WcW, Apr 09 2010 The latter, although thanks for pointing out a most amusing coincidence-- BunsenHoneydew, Apr 09 2010 I don't think the canal's achievable. So.... scoop the plastic out of the Pacific Garbage Patch, recycling it into a continuous hosepipe. Then string the hosepipe across Australia, all the way to the sub sea level desert. Next... start the siphon. More Ren & Stimpy solutions in the works.-- sstvp, Apr 09 2010 [sstvp]: The point of all the mathematics above - both mine and that of [Consul_Flamincus] - is to establish the size of the infrastructure needed, within an order of magnitude or so. No "hosepipe" is going to provide enough water to counter the rate of evaporation, unless it is (by my calculations) around 25 meters in diameter, which makes it less a hosepipe and more a major work of engineering. By the time you get to that scale of construction, you may as well go the whole hog and build something to last millenia.
Perhaps a gigantic mirror in geocentric orbit could focus enough sunlight to vaporise the rock in the way. Otherwise we are going to need a lot of nukes, or a lot of shovels.-- BunsenHoneydew, Apr 09 2010 Halfbaked comrades: an alternative plan has presented itself [link]-- BunsenHoneydew, Oct 21 2010 Reducing the evaporation rate by half by various methods [Australian Inland Sea II] would reduce the rate of inflow water required by the same proportion, and ditto the cross-sectional area of the canal/pipe. From previous calculations that gives (at 1m/s flow rate) an overland canal 25m wide x 10m deep, or an inflow pipe of around 17-18 meters diameter, reducing further if the flow rate can be increased.
As this reduces the cost of the whole enterprise considerably, it seems likely that a combination of both approaches would be optimal.
It would not affect the size of a separate return channel for brine.
It also has just occurred to me that construction of the brine return channel would be most easily accomplished along the same route and at the same time as digging the inflow canal. If as a pipe, it could be cut-and-covered below the canal - or, even easier, a simple ditch with or without a lid on it.-- BunsenHoneydew, Oct 31 2010 Taking a ruler to Google Maps [link] suggests a canal length of 360km, via Lake Torrens. Some of that will be above sea level and some below, so let's average that out to zero.
Volume of earthworks required:
360,000m x 25m x 10m = 90,000,000m^3
Assuming diggers and dozers capable of moving 100m^3 per machine per hour, that's 900,000 machine-hours. A fleet of 1,000 machines could dig this canal in a mere 900 hours, or 24 standard Australian work weeks of 37.5 hours. 8 weeks if we run three shifts, less again if we run the machines 24/7.
Two months! Four months even if we don't put in place an evaporation strategy and thus have to dig twice as large a channel. Or to put it another way, with fewer machines and/or workers, easily achievable in a year. Let's get cracking already!
(Unless I've fouled up my sums somewhere - anyone?)-- BunsenHoneydew, Oct 31 2010 // Reducing the evaporation rate by half / would not affect the size of a separate return channel for brine. //
Oh wait .. of course it would. Importing half the seawater means importing, and thus needing to remove, half the sea salt. Figuring brine at depth concentrated to 4x the salinity of seawater means a return channel of 1/4 the size of the inflow, thus ~65 m^2 cross section, or a pipe 4.5m in diameter. Giving it a drop of 1m per km would mean the outlet is 375m beneath the sea-- BunsenHoneydew, Oct 31 2010 //brine at depth concentrated to 4x the salinity of seawater// You seem to suggest that the salt will migrate to the bottom, forming a layer of extra salty brine under a layer with a salinity closer to that of sea water. I'm fairly sure it doesn't work like that; the only place that the salinity can increase is at the surface, where evaporation happens.
You need a specific mechanism to establish and maintain that salinity gradient, for example separate ponds that produce highly saline water, which is then gently introduced to the bottom of the main lake.-- spidermother, Dec 05 2010 It's called "gravity"; you should look into it, it's quite a handy sorting mechanism for fluids with different densities.-- BunsenHoneydew, Dec 09 2010 //sorting mechanism// How do regions of hypersaline water form in the first place? What prevents water subject to evaporation (at the surface) from sinking when it is just a little bit saltier than the surrounding water?
Your salinity siphon should work, but it relies on the high salinity in the lake as a whole, rather than a strong salinity gradient within the lake.
As far as I know, it is only possible to create a strong salinity gradient in a body of water by (for example) floating a layer of fresh water on a layer of (preexisting) saline water. It is not an equilibrium situation, and should not be expected to arise spontaneously from evaporation at the surface.-- spidermother, Dec 09 2010 Surely it would be easier to flood the coastal areas first, and work inwards?-- MaxwellBuchanan, Dec 09 2010 Nah, the contractors need a base or bases of operations, and most of the urban & suburban infrastructure's coastal. Why build new temporary cities inland?-- mouseposture, Dec 10 2010 //How do regions of hypersaline water form in the first place? What prevents water subject to evaporation (at the surface) from sinking when it is just a little bit saltier than the surrounding water?//
It's a good question.
Apparently the Dead Sea was stratified until the freshwater input was reduced. After a while the surface was saltier than the underlayer, but for a while it was warmer and so still less dense. When it cooled down, mixing occurred. Restratification is now occurring (according to Wikipedia).
I don't know if stratification would happen with sea-water as the input. Even if it doesn't, it would be straightforward to arrange for the water to flow through a series of ponds.-- Loris, Dec 10 2010 Solar Lake sometimes becomes highly stratified w.r.t. salinity, but that is due to exceptional and complex conditions, and is temporary. I mainly wished to challenge the assumption that it would happen as a matter of course in a large salt-water fed lake.
And I have looked into "gravity", and various types of stratification, having studied university physics, freshwater ecology, and marine ecology to some extent; my recollection is that when denser water occurs near the surface of a lake, due to salinity or temperature, the result is usually fairly complete mixing rather than the migration of the denser water to the bottom.-- spidermother, Dec 10 2010 ""Assuming diggers and dozers capable of moving 100m^3 per machine per hour, that's 900,000 machine-hours. A fleet of 1,000 machines could dig this canal in a mere 900 hours, or 24 standard Australian work weeks of 37.5 hours. 8 weeks if we run three shifts, less again if we run the machines 24/7.......
......(Unless I've fouled up my sums somewhere - anyone?) — BunsenHoneydew, Oct 31 2010
My god man. A mining excavator might be able to work that fast in loose material but that would require multiple dump trucks running along side and bulldozers to support on both ends. More dump trucks depending on the distance to the dump end. If rock and blasting are involved you will be nowhere near that figure. Multiply your machine hour figure by 4. Then multiply by 1.25 for breakdowns and weather. Then multiply the per unit by 10 for every unit of rock that you need to excavate. Then you might be in the ballpark. Consider the "big dig" here in the states when you contemplate the time and budget potential.-- WcW, Dec 11 2010 Baked?-- nineteenthly, Jan 03 2011 Not yet.-- WcW, Mar 05 2012 On the contrary, I believe that implementation of this idea would constitute 'unbaking' the Outback, in more ways than one.-- Alterother, Mar 05 2012 Re-doing some of my earlier calculations in light of objections.
Firstly, I apologise to [spidermother] regarding my assumption that a hypersaline bottom layer would form by gravity sorting alone. I believe you are correct: without other factors, the lake would most likely undergo substantial mixing and no saline gradient would form.
There are two factors that might make this happen though - one is that the cyclic expansion and contraction of the lake via filling and evaporation would shrink the surface area. The shallowest areas would be dry first, and thus the more concentrated brine (concentrated by evaporation) would tend to pool in the deeper areas.
Then, every seven years or so, a flood of fresh water would arrive overland. This would tend to ride over the top of the denser brine, I think, and mixing should be minimal.
Still, if this proves false, the alternative idea of creating evaporation ponds around the shallower edges of the lake is viable - while requiring a level of manual intervention and maintenance, this might allow us to create a highly concentrated brine slurry at (wild guess) 10x the concentration of seawater, thus reducing by a factor of 10 the size of the needed brine return channel.
[tbc]-- BunsenHoneydew, Nov 04 2016 Secondly, taking into account the objections of [WcW] regarding the earthworks, and some notably faulty assumptions of mine:
// 15 teralitres of annual evaporation. Thus we need an inflow of / half a megalitre per second. when the next flood fills the lake, it should stay full for good. // - [BH]
I've ignored the input from later flood events, which I should probably not have done.
// Volume of lake Eyre when full is 34cubic km, or 34 million megaliters. // - [CF]
Divide that by seven years to obtain an average rate of freshwater inflow, and we have 154,000 l/s - which is around 30% of our (previously calculated, to match the loss via evaporation) required half-megalitre/s inflow from the sea, leaving us ~350,000l/s to import.
If we can increase the inflow speed to 5m/s (18kmh / ~11mph), that gives a cross-sectional area for the inflow channel of 70m2 - a barge canal 10m wide by 7m deep, or a tunnel of diameter ~9.5m. This is large, but not out of the realm of such large tunnelling projects as say the Chunnel. The largest tunnel-boring machine used to date (per wikipedia) is 19.25 metres in diameter.
Increase the area of the tunnel by two (diameter by root-2) to 140m^2 / ~13.5m, and you have a half-full, barge-navigable tunnel under the mountains.
Given the extreme flatness of Australia, particularly in the Eyre Basin, I'm going to take a wild guess that say 50km of the 360km route would require tunneling, and the rest of the route can be completed by earthworks. While this puts it up amongst the largest projects ever constructed, it's not an order of magnitude larger than things humankind have built to date. Consider the Panama and Suez Canals: built to take ocean-going shipping, whereas here we're building a much narrower channel for water flow, with barge traffic being an optional bonus. For the purposes of wild approximation, I reckon you can trade length for girth (shush you at the back) at about 1:1.-- BunsenHoneydew, Nov 04 2016 For comparison, per wikipedia:
Channel Tunnel Length: 50km (31 mi) Diameter: two x 7.6m (25ft) rail tunnels + 4.8m (16 ft) service tunnel Construction time: six years Construction cost: £4.650bn (£13bn / US$14.5bn today)
Seikan Tunnel Length: 53.85 km (33.46 mi) Diameter: 11m (36ft) main tunnel + 4m - 5m service tunnel + 3.6m - 5m pilot tunnel Construction cost: US$3.6 billion (1988) US$7.5bn today
Suez Canal: Length: 193.30 km (120.11 mi) Depth: 23 - 24m (75 - 79 ft) Width: 205 - 225m (673 - 738 ft) Locks: none Construction time: 10 years Construction cost: ????
"New Suez" Canal (upgrade / second lane) Length: 34km new + 37km deepening and widening of existing channel Construction time: 2.5 years Cost: US$8.4bn (2016)
Panama Canal: Length: 77 km (48 mi) Locks: 18 (3 up, 3 down, 3 lanes) Excavation: 153 million m3 (23m m3 by the French and 130m m3 by the US) Construction time: 18 years (8 French, 10 American) Cost: hard to calculate, due to aborted French project and various payoffs to Colombia / Panama. I make it about US$622m at the time, or US$15bn in 2016.-- BunsenHoneydew, Nov 04 2016 70m2 x 360km = 25.2m m3 of excavation. Let's triple that to account for overburden and call it 75m m3.
Give it a 14 year completion target (two flood cycles), three shifts a day, and 48 work weeks of 37.5 hours per year.
14 x 3 x 48 x 37.5 = 75,600 hours
Hence we need to move ~1,000 m3/h
Let's assume [WcW]'s objection to my previous calculation of moving 100m^3 per machine per hour is correct, and that figure is ridiculous. Make it 10 m3/hr instead. That means 100 machines and drivers - double that for maintenance, trucking away and dumping, and associated road building etc and call it 200. Or if you prefer, throw 1,000 (200x5) machines and drivers at it and complete it in 2.8 years.
Panama Canal (figures from previous anno) US$15bn to excavate 15m m3 with yr1900 technology= $15,000/m3 Let's 1/5th that for 21st century tech $3,000/m3 x 75m m3 = $225bn
DOABLE.-- BunsenHoneydew, Nov 04 2016 Hold on a second. Why excavate 70m2? Shirley, if you excavated a fairly modest ditch - maybe 5m2 - there would be a toronto of water running through it that would rapidly deepen and widen the channel, no?-- MaxwellBuchanan, Nov 04 2016 I really love this idea.-- theircompetitor, Nov 04 2016 //Let's 1/5th that for 21st century tech $3,000/m3 x 75m m3 = $225bn//
Oh yeah, the digging will be cheaper. We have monstrous equipment that can do all kinds of things.
//US$15bn to excavate 15m m3 with yr1900//
They had the massive advantage of 1900 admin and safety. Then it was: "I need a hole, here's a spade and some money... dig" Now: "OK, well, it looks like we have the bare bones of the oversight committee regarding diversity in the risk assessment team. Now, you all know that spiders alone will require nearly 1400 individual risk assessments, we're going to need some serious decision making on whether we need to consider crocodile issues before we flood the basin."-- bs0u0155, Nov 04 2016 // if you excavated a fairly modest ditch - maybe 5m2 - there would be a toronto of water running through it that would rapidly deepen and widen the channel, no? // - [MB]
That is what happened to the Mississippi River Gulf Outlet Canal [link]. As long as one dug out the hard rock sections to adequate width, you may well be correct that the water can do the remainder of the work.
// Due to rapid erosion of the surrounding marsh, the canal was already as much as three times wider by 1989 than as originally constructed [in 1965]. When MRGO was built, the channel was 650 feet (200 m) wide at the surface. In 1989 the average width had become 1,500 ft (457 m). //
Now, we won't be working through marsh, but if we follow the ancient channel that connected Lake Eyre to the sea, it will mostly be silt deposits and some soft sedimentary rock.-- BunsenHoneydew, Nov 04 2016 Gee, that Daihuofung tunnel was cheap.
85km x 50m2 =4,250,000 m3 / US$750m = half a cent / m3 (US$0.00566666666)
Shirley I've dropped a zero there somewhere?-- BunsenHoneydew, Nov 04 2016 Eyre channel:Daihuofung
360km/85km x 70m2/50m2 = 4.11764705882353:1 x 1.4:1 ~ 6:1
Cube that, because we're dealing with volume, and you get 216:1
x US$0.75bn = US$162bn
That's in the ballpark of the previous $225bn calculated from the Panama Canal costs, and it's still assuming a tunnel all the way.
What the heck, halve that to $80bn (assuming most is excavation and not tunnel) and it's still less than even the cheapest manned Mars mission proposals. And that's without any attempt to reduce the evaporation rate, as per [Australian Inland Sea II]-- BunsenHoneydew, Nov 04 2016 Double checking that last calculation, stand by-- BunsenHoneydew, Nov 04 2016 Eyre channel:Daihuofung
360/85 (length) x 70^2/50^2 = 4900/2500 (area) = (4.11764705882353 x 1.96):1 (volume) ~ 8:1
x US$0.75bn = US$6bn
What the hey? Help, I need a quantity surveyor. [marked-for-engineering]-- BunsenHoneydew, Nov 04 2016 Maybe these figures aren't so ridiculously small after all. The Tenn-Tom barge canal [link] mentioned way back in 2004 by [NickB] is almost exactly the same length and (minimum) cross-sectional area, and cost US$4.65bn in 2016 dollars.-- BunsenHoneydew, Nov 04 2016 //it's still less than even the cheapest manned Mars mission proposals.//
Yeah but, at the end of the channel-digging, you still won't have anyone on Mars.-- MaxwellBuchanan, Nov 25 2016 It seems that no one has ever calculated the area, much less the volume, of Australia below sea level/Austrailian air space below sea level. I would like to know by how much it would lower sea level. An inch at the most, Shirley.-- Voice, Nov 26 2016 Well, a quick Google of maps suggests that the inland sea would occupy maybe 10-20% of Australia (say 20% to be optimistic) and have a depth, on average, of maybe 20 metres. That would lower the world's oceans by about 10cm.-- MaxwellBuchanan, Nov 26 2016 For Goddess's sake don't tell Trump, he'll take it as a license to spew.-- Voice, Nov 26 2016 Maybe those submerging countries will give the Australians some money to take on that 10 cm of sea level. That would open up a lot of valuable beachfront property. Florida alone should be good for a billion or so.-- bungston, Nov 30 2016 Since the added water is fresh, perhaps mining vast quantities of salt inland and adding it to the ocean would cure the upcoming problem (for the ocean ecosystem) of reduced salinity.-- FlyingToaster, Nov 30 2016 random, halfbakery