An alternative method of creating a permanently-full Lake Eyre in central Australia. [see link - The Australian Sea - for background] Also applicable to the various similar proposals such as "Lake Death Valley".
Lake Eyre fills naturally with floodwaters approximately every seven years, after heavy rains in the vast catchment area stretching up through South Australia, Queensland and the Northern Territory. While full, the lake is a haven for wildlife, particularly migratory birds, and contributes to estimated billions of dollars in extra agricultural production by encouraging rains* downwind.
Then, within a few months, it evaporates, leaving the more familiar barren salt plain (below sea level).
The enemy is the vicious heat and sun of the Outback. So let's do something about that - shade the sun from striking the water, and slow the rate of evaporation. While we're at it, let's put that solar radiation to good use.
Let's begin with a pilot project.
"Even in the dry season there is usually some water remaining in Lake Eyre, normally collecting in a number of smaller sub-lakes on the playa." [wikipedia - link]
Picture small square or rectangular barges carrying an array of photovoltaic panels, a small wind turbine and tower, a high voltage inverter, and connecting cables. The sun does not fall vertically, even at noon in midsummer, so raise the panels a couple of meters up - this way, the barge and the array together will be shading the largest possible area. Use the cheapest panel technology available, as efficient conversion as measured by area is not an issue - in fact, shading a larger area is a positive, not a negative. Therefore we can aim for efficiency in dollar terms instead.
All equipment will need to be suitably toughened against the brutal environment - salt, high winds, sandstorms, highly saline water, and extreme temperatures.
Dot a number of these pontoons across the remnant lake. Aim to cover a proportion of the lake's surface at midday midsummer - perhaps 25%, 50%, 75% - whatever your calculations show is desirable, or whatever your funding allows. Start with a small area, or a small proportion, and add to it over time.
100% shade, although effective, would be the deathknell of any biological activity in the water. Spacing between the barges also allows for towing barges in between for installation and maintenance, access by small craft, and to send in skimmer craft to harvest any blue-green algae outbreaks as bonus biomass.
(Calculations to follow, maybe. Of course we will need to take into account that part of the evaporation due to high ambient temperatures, rather than direct insolation)
The pontoons are linked in a chain by cables or rods to maintain their spacing, and to carry the HV transmission lines. These are fed to a substation on the shore which boosts the voltage once more for transmission to the national grid.
Each barge consists of a ring (round, square, rectangular) of pontoons with a void in the centre. Across this void stretches a polymer mesh or gridwork, which is planted with salt-tolerant grasses, shrubs and other plant species. This will infill the void with shade, as well as providing a wetland-like habitat for birds, insects and eventually other animals (initally, probably reptiles). The animal life attracted to these shaded, floating grassy islands will provide manure to make the micro-environment self-sustaining. The cool, shaded, nutrient-rich water underneath will encourage fish and other aquatic species to take up residence, or they can be introduced (mussels for example). In addition, the halophile plants draw salt from the water, lowering the salinity. Seeding with high-value ocean fish species is a future option.
Periodically the plantlife is harvested and returned to a facility at the natural shoreline, where it is used as, or converted into, biofuel. It can either be burnt directly to generate steam for a conventional electricity turbine, or fed into a methane digester and the methane so used. If suitable species are chosen, it can be converted into liquid biofuels for transport (ethanol and/or biodiesel), using the abundant sunshine as process heat. Here again, efficiency by cropped area is a secondary consideration to efficiency by cost. Process waste (ash or sludge) is used on-site as a soil improver for landscaping around the facility and any worker residences. As production expands, this waste stream is turned to aid in the plantation, afforestation and stabilization of the Lake Eyre shoreline.
The grid arrangement and standardization of barges lends itself well to mechanized harvest.
Now you are up and running, and generating a diversified income stream. This aids you in funding future expansion. Observe, monitor, take copious notes. Adjust grid spacing and proportion of shade as observation and theory dictate.
New barges are added to the edges of the grid, expanding outwards from the pilot area, one ring at a time. These are added continuously during dry periods, simply trucked into place, dropped onto the saltpan and connected up to their neighbours. They are wired into the grid, and immediately begin contributing to your electrical sales. Upstream infrastructure to the national grid is upgraded as required.
Initially, these added barges will be resting on the salt pan. Over the approximate seven years between flood events, a large area is thus shaded. When the next flood arrives, they will float with their neighbours, and can be similarly planted. Once the flood has passed, a larger lake stays behind.
Continuous barge manufacture provides a small but steady regional industry and employment opportunity, synergistic with local (South Australian) industry strengths such as small boatbuilding, electrical contracting and skills from the mining industry (welding, fabrication, logistics etc). This helps to stabilize employment against the boom/bust cycle of the mining sector. Standardized barge and component design allows for a broad and competitive supply stream.
Lather, rinse, repeat. Your green, island-dotted lake expands. Fish, birds and small animals abound. Perhaps another playa lake or two nearby have also been thus developed, either by your project or an independent one (though standardized to ensure compatibility), and they meet and merge.
Over a few decades, it should be possible to eventually shade the whole of Lake Eyre, and create a permanent body of water with all of the benefits detailed at [The Australian Sea], along with viable and ongoing export industries in energy, food and biomass.
As the permanent lake approaches the edges of the salt basin, work begins on dredging out the (cheap, shallow) barge canal from Lake Eyre to Spencer Gulf. Once open, this will allow the flow of water from the lake to the ocean, and begin the process of permanently removing the salt from the lakebed. In addition, a direct freight channel will be opened up for the export produce of the Lake Eyre Corporation, and the import of new infrastructure.
Grand thoroughfares are opened up between the rows of barges, and their connecting structures submerged, to allow the passage of both freight and maintenance vessels, and pleasure craft for tourists, bird watchers, anglers, hunters and holidaymakers. Double- and quadruple-sized (and so on) barges are added to the grid to create small forests and space for holiday cabins, and eventually permanent homes and farms. As the salinity drops, plant species are adjusted (or, in barge zones set aside as wilderness, selected) to suit the new, less saline environment.
Judging by the experience of similar island-dotted lakes (whether floating, as in South and Central America and south-east Asia, or dredged and sculpted out of marshlands like the pre-Columbian chiñampa system of Mexico City), the new, permanent, inland sea could become one of the most agriculturally productive sites on the planet, as well as contributing to stable and productive agriculture throughout the south-eastern Australian agricultural region. Plus, abundant renewable energy.
*I am aware that by lowering the rate of evaporation, we are lessening the potential for downwind rainfall during flood events. I posit that the permanence of the lake more than makes up for this. Rather than a short-term rain boost, the permanent lake should provide a more steady climate with more even rains over the years, and help to break the cycle of drought and flood which has so characterised Australian agriculture, and contributed to its economic and environmental instability.-- BunsenHoneydew, Oct 21 2010 The Australian Sea The_20Australian_20seaGulherme, 2003 [BunsenHoneydew, Oct 21 2010] Lake Eyre http://en.wikipedia.org/wiki/Lake_Eyre [BunsenHoneydew, Oct 23 2010] Lake Torrens http://en.wikipedia...rrens_National_Park [BunsenHoneydew, Oct 23 2010] Google Map: Lake Torrens, Port Augusta and Lake Eyre South http://maps.google....440651,7.091675&z=8 [BunsenHoneydew, Oct 23 2010] Uros http://en.wikipedia.org/wiki/UrosFloating island people of Lake Titicaca [BunsenHoneydew, Oct 28 2010] Atlantropa http://en.wikipedia.org/wiki/AtlantropaDrain the Mediterranean! [BunsenHoneydew, Oct 28 2010] Floating Islands http://en.wikipedia...iki/Floating_island [BunsenHoneydew, Oct 31 2010] Lake Chad http://en.wikipedia.org/wiki/Lake_Chadis disappearing! [BunsenHoneydew, Oct 31 2010] Chinampa http://en.wikipedia.org/wiki/ChinampaA method of ancient Mesoamerican agriculture which used small, rectangle-shaped areas of fertile arable land to grow crops on the shallow lake beds in the Valley of Mexico. [BunsenHoneydew, Oct 31 2010] Floating Trash Islands http://www.lowtechm...g-trash-island.htmlthe low-tech, recycled version of the pontoons. [BunsenHoneydew, Jan 13 2014] Floating Islands International https://www.floatin...ndinternational.comThe very thing - mass produced from recycled plastics. With lots of Science and case studies in using them for bioremediation and water treatment. [BunsenHoneydew, Jan 28 2020] Further thoughts:
The floodwaters that reach Lake Eyre are rich in silt and agricultural runoff. The suspended roots of the barge plant systems should filter and capture some of this silt, providing another source of free biomass and fertilizer, and progressively filtering the water as it flows downstream to the canal to the ocean.
Additionally, Lake Eyre is fairly shallow. Perhaps the continuous capture and deposition of this silt will cause mounds to grow underneath each barge, eventually converting them from floating islands into true and permanent islands, like the Mexican chiñampa.-- BunsenHoneydew, Oct 21 2010 you've done way too much thinking to not make it a real grant proposal.-- Voice, Oct 22 2010 Thankyou, [Voice]. It kind of came to me all in a rush.
A possibly cheaper alternative would be to mount mirrors on each barge and use them to focus the sun on a solar power tower at the northern end of the lake, or a number of them dotted about.
Course, leaving the whole power generating aspect aside and just building shade and habitat barges would greatly simplify and cheapify the operation, whilst reducing the ability to self fund. One could still harvest biomass for the uses originally detailed.
Other worthy objections raised at my facebook account, where I have placed a link to this idea:
"The floating PV cells might not pay for themselves and the grid before they get covered in bird crap and scoured by salt and sand." - JG
Answered as per above.
"wondered why you would need cables joining them all, everything could be self contained/regulating.
then i began to consider tinier barges/boats purely existant for shunting some sort of power storage around (mobile batteries with engines, possibly even with tug abilities for when necessary.
tiny floaty things with wheels for when its dry of course, and big puffy wheels for when its muddy..." -WA
My reply to the second: "Cables? To export the power. And moving barges around takes energy, which leaves you less to export.
Leaving the whole energy generation aspect aside, and just building shade and habitat barges, would make the whole exercise cheaper, but not self-funding.
Cables/rods also regulate the space between the barges to maximise shade."-- BunsenHoneydew, Oct 23 2010 Initial calculations:
Surface area of Lake Eyre (when full) is ~9,000km^2
Assuming barge sizes of 10m x 10m, with 10m channels between them (to allow passage of same-sized barges under tow), and shade from the raised panels of equal size, gives 50% shade over the lake, and one barge per 20m x 20m square. There are 50 x 50 = 2500 of those squares per km^2, giving a total of 22.5 million barges.
Now, to deploy those over a century would require a rate of ~4,000 to 4,500 a week. Which is rather a lot, to be honest.
Doubling the size of the barges and spacing to 20m still gives 50% shade, 1/4th the number of barges per km^2 and thus deployment of around 1,200 (larger and more unwieldy) barges per week.-- BunsenHoneydew, Oct 23 2010 Lake Torrens [link], to the south of Lake Eyre, is approximately half the size (~5,000km^2) and much closer to the ocean. It has the disadvantage for the current proposal that it has only been filled once in the last 150 years.
The much reduced distance from the head of Spencer Gulf - a mere 60km [link] as opposed to ~350km - makes it a much more viable target for filling from the ocean by means of pipe or canal. I see there are also a number of much smaller lakes dotted between Torrens' southern end and the Gulf, which would be ideal for pilot projects of either the ocean-filling or evaporation-reduction type.
Torrens itself also covers the bulk (some 240km) of the overland distance from the ocean to the southern end of Lake Eyre South, which makes it an unavoidable part of any plan to fill Eyre from the ocean.
Lake Eyre South, although separately named, fills approximately as often as Eyre itself and has a much smaller surface area, again making it a suitable target for an advance project.
So perhaps a combination of methods is required: both ocean filling and shade reduction. Extensive shading (perhaps 100%) of the small lakes to the north and east of Eyre to encourage retention and on-flow of the rare overland flows from rainfall, starting as far from Eyre as feasible and working inwards. At the same time, ocean filling and shading of the string of smaller lakes between Port Augusta and Lake Torrens, starting at the southernmost as a pilot project.-- BunsenHoneydew, Oct 23 2010 The backup plan is to cover the lake with ping pong balls and expanded polystyrene foam waste, although I figure most of that is likely to be lost to the wind.-- BunsenHoneydew, Oct 23 2010 The saline outflow you propose might be a problem. The lake is 50ft below sea level. Equally, the number of barges you propose is a little ambitious, though possible if you were to divert the entirety of Australia's automotive industry to building them.
The biggest issue will be the ambient temperature, which sees about 6 months of the year at temperatures averaging above 40deg C or 100deg F. Evaporation is a serious problem with almost any standing body of water, once you go inland any distance.-- infidel, Oct 23 2010 I'm not sure the local auto industry produces anything like 4,000 cars a week. Even granted that the barges are much simpler than a car, this is certainly a similar scale, sure.
You are quite right about ambient temperature of course. It's a huge factor. It may not be feasible with anything less than 100% shade, or even then. We definitely would need to start with a smaller lake and study it closely.
The scale here even suggests that floating a giant solar sail in space over the site might be of a similar order of feasibility.-- BunsenHoneydew, Oct 23 2010 The Austraian industry produces about 300,000 large cars per annum, from memory. Depending upon the complexity required for your barges, it may be possible.-- infidel, Oct 23 2010 The complexity should be fairly low.
For the simplest (non-power generating) version:
Pontoons: Extruded rigid plastic tubes of identical diameter; cut to length and hot pressed to seal the ends.
Mesh: Manufactured in a continuous roll process at 10m width, incorporating seeds/cuttings and starter medium.
Tower/shadecloth: Extruded structural members, roll process cloth.
These would all be trucked/zepellined to the site and assembled locally. Transport costs would be substantially reduced if inflatable pontoons were used, but this would need to be weighed up against durability and longevity.
The generating equipment should be no more complex than a small grid-connected home PV system. Overall, each unit should be about as complex to build as (wild guess) 1/5 of a small car, if that. Leave out the wind generators, and there are no moving parts or bearings, far lower structural stresses to build around, and much lower maintenance costs - along with much lower initial income.
Over the longer term, I could envisage barges being crafted in situ from reeds harvested from the previous rafts, after the manner of Egyptian/South American reed boats and platforms.-- BunsenHoneydew, Oct 25 2010 It should be clear by now that this is a multi-generational endeavour. At full deployment, the Eyre/Torrens system could support a permanent resident population of thousands to millions, living and working on the islands and shoreline; fishing, trading, farming, foresting, and hunting.
As to the question of evaporation by ambient air temperature:
The outermost ring needs to be an unbroken barrier wall of upsized barges, supporting a permaculture windbreak forest. This will help to cool and slow the hot winds sweeping across the lake. The ring-forest is added to and extended as the barge system within expands, until it runs aground on the shoreline, and forms the permanent forested boundary of the lake system. Further windbreaks across the middle of the system will be progressively installed as well, to extend the range downwind of the moderating effect.
[marked-for-engineering]: estimates of evaporation due to direct insolation, ambient temp, and wind.-- BunsenHoneydew, Oct 25 2010 ...but the //estimated billions of dollars in extra agricultural production by encouraging rains downwind// depends on evaporation, so you'll lose this benefit if you restrict evaporation.Also, what's the legal position? When the whole thing's up and running, the local aboriginal community may assert a prior claim to the entire area and demand the revenues you're receiving from electricity production.-- hippo, Oct 25 2010 1/ Covered in the original post 2/ You say that like it's a bad thing.
It's not like I'm personally going to go out and build the thing as my very own Inland Empire. This is a national to international scale project over a decades to centuries timescale. Why would I care whether it's whitefellas, blackfellas or yellafellas getting rich off of it?
Title determination and local consultation would be the first steps, not the last. Let them set it up and run it, with suitable partners, or extract fair rent, or whatever. Why would this be a bad thing - unless you think native title is somehow different to "real", white man's title, and doesn't actually represent real ownership and the rights that come with it?
The goal is improved weal for all, financial, economic, social and environmental. Arguments about what particular system of economics and jurisprudence prevail are well outside the scope of this discussion. If anything, I would assume and prefer that the locals were involved, intimately and early, whatever the model.
In my fantasy, the economic, racial and social diversity of Eyretopia is as complex as the ecological.-- BunsenHoneydew, Oct 25 2010 Ah yes, sorry - I didn't read the footnote. I wonder what the salinity of this sea would end up as? On the one hand much of the water would be freshwater, from rain, but then you might get some of the salt plain dissolving into the sea to make it salty. Also, if any evil geniuses want an undersea lair, it would make sense to build it on the future sea-bed now, as construction costs will be lower.Actually that makes me think - it would be sensible to build an entire undersea city while you're doing this. You'd have attractive places to live, interesting views of undersea life, and a constant, mild temperature, with no need for air-conditioning. The obvious way to do it would be to build the living units and the barges in a single contruction - so like a houseboat, but with the living quarters entirely submerged and accessible only through a trapdoor on the barge.-- hippo, Oct 25 2010 The salinity cycle over flood/dry-out events is discussed in the wikipedia article. Extrapolating from that, it seems like the longer term shaded lake would maintain a fairly high level of salinity until salt removal (by halophile plant harvesting, industrial extraction, or seawater flushing) takes effect.
Another comment from elsewhere pointed out that deep water evaporates much slower than shallow water. So perhaps earthworks during the dry can be a part of the project as well. Bulldozers start at the lowest point (15 meters) and shove the salt and clay crust outwards, creating a larger 15 meter pool. The flood events would create a lake of smaller surface area, but deeper and more long-lasting. The overburden can be built up around the outer edge to create terraced windbreak berms, which are capped and sealed with clay and planted out.
On the other hand, this is several orders of magnitude larger a project than digging a 15 meter deep channel to the sea via Torrens.-- BunsenHoneydew, Oct 27 2010 Energy generation: 9,000km^2 (Eyre) + 5,000km^2 (Torrens) + 1,000km^2 (smaller lakes and canals), 25% covered with (cheap) 5% efficient PV panels @ 1kw/m^2 insolation = 187,500 megawatts
Add in the 25% area cropped for biofuels at (wild guess overall) 2.5% efficiency and the total comes to = 281,250 megawatts-- BunsenHoneydew, Oct 27 2010 <voice of [8th/7]> silly humans think they can slow the burn </vo1.14285714>-- daseva, Oct 27 2010 This could be a good use for a giant space mirror. The shade would allow a lake and since the light is kept off Earth, it's got to help global warming a bit...-- saedi, Oct 28 2010 Rough calculations regarding earthworks to convert the lake fringes into a chinampa system [see link].
Deepest point is 15 meters, shallowest is 0. Let's say 5 meters is deep enough, and we leave that area undisturbed. At a wild guess, that leaves 1/3 of the lake surface (3,000km^2) to convert. Let's also assume a salt crust of 50cm to remove. That alone is 1.5 billion m^3, leaving an average depth of 3m, of which we want to convert say half (1,500km^2) to 1m above sea level, leaving navigable channels in between.
This zone has an average depth of (5.5m/2=) 2.75 meters. Therefore to bring that up to >1 meter above the waterline will require (3.75m*1500km^2=) 5,625,000,000 m^3
Assuming a bulldozer can push (wild guess) 100m^3 per hour, that's 56,250,000 dozer-hours or ~30,000 dozer years (8 hour days, 48 x 5 day working weeks per year).
So 1,000 dozers could accomplish this in 30 years, or ten years working 3 shifts.-- BunsenHoneydew, Oct 31 2010 A slight issue - it turns out that Lake Torrens is in fact 50 meters above sea level. There are alternative routes via Lake Gairdner or Lake Frome which have shown up in searches.-- BunsenHoneydew, Dec 04 2010 Use a portion of the solar panels on the barges to generate seacrete underneath themselves. When it gets close to the surface, transfer a little bit of dirt and one small panel (to maintain it) onto the new island, and move the barge to its next location. This acts to reduce the salinity (well, Mg and Ca components, anyway) and reduces the number of barges.-- MechE, Jun 15 2012 I like that, [MechE], I like that.
I wonder if there is an insoluble compound which can be relatively easily generated from (mostly) NaCl, by combining with (a little) other available stuff in the water. That would both desalinate the water, and create bulk material (like seacrete) for building and earthworks.-- BunsenHoneydew, Jan 13 2014 This is a great idea, but wrong.
What you need is duckweed. Or water lillies. Or some other highly-invasive floating organism.
In the UK, we have been working for some time on developing an essentially aquatic, surface-dwelling rabbit. We could send you a few if you like.-- MaxwellBuchanan, Jan 13 2014 I put an alternative concept to this discussion. Once every seven years or so there is an abundance of water flowing into this system. I see that where this water comes from does not have the high evaporation rates that are in the inland areas.
Assume that we could develop a series of catchment dams in the headwaters area of this river system that could hold sufficient water to allow for a monitored release of water over a given period of time - say 10 years. We could use that release to drive a hydro electric scheme. That would maintain an income structure to maintain the project.
It would also provide a constant flow of water into the basin and out to sea, keeping the salinity under control. An added advantage would be to level out some of the waterflow into the region, reducing severe flooding impacts on the new ultra-improved agriculturally based communities that will be able to develop, and provide much needed support to this dwindling sector.
Excavate numerous areas to have deeper lake areas, and utilise those areas to irrigate the surrounding countryside to establish forested areas of a mix of deciduous and evergreen trees and pastured areas interspersed.-- laterally thinking, Feb 20 2014 Hold up.
Evaporation from the lake sustains agriculture downwind.
So we're going to slow the evaporation??-- sstvp, Feb 21 2014 The "lake" only fills with water every seven years or so. The proposal is to develop a permanent body of water on the site. The downwind boost to agriculture over the flood/drought cycle would be evened out over time, not eliminated.-- BunsenHoneydew, Jan 20 2015 //Assuming a bulldozer can push (wild guess) 100m^3 per hour, that's 56,250,000 dozer-hours or ~30,000 dozer years (8 hour days, 48 x 5 day working weeks per year)//
Nukes will do that way faster...-- bs0u0155, Jan 20 2015 Nukes would make shade too, but I understand the area can get windy, and so the airborne soil would probably not persist very long locally.-- bungston, Jan 21 2015 Hey, [laterally_thinking], let me be the first to welcome you to the halfbakery.
I like this statement in the original idea:
" All equipment will need to be suitably toughened against the brutal environment - salt, high winds, sandstorms, highly saline water, and extreme temperatures. "
I picture all that equipment with hats, sunscreens, and sunglasses.
It reminds me of [jutta]'s response to the question " how do you reinforce steel ? "
" You're steel, yes you are..."-- normzone, Jan 22 2015 "This is a great idea, but wrong."
[marked-for-tagline]-- BunsenHoneydew, Jan 28 2020 random, halfbakery