The climate change debate continues.

[pmccarthy]

I have a copy of a speech by Lang Hancock proposing to build the channel with atomic bombs.

 

 

[Methusala]

I believe that it is established fact that rainfall is greater to the east of the line that demarcates wheat cropping from undisturbed bushland in West Australia. A good read is "The Bush" by Don Watson. He has produced a well researched essay describing the changes to Australia's landscape since the arrival of Europeans over 200 years ago.

 

 

[Old Koreelah]

Perhaps we should consider making a major change in Australia's climate by attempting to restore the Inland to what it was about 60 million years ago. Could we start filling Lake Eyre to provide a source of moisture for the eastern half of the continent?...

 

That idea has always intrigued the engineer in me, OME. Relatively cheap to do, just run a pipeline north to bring seawater from the gulf. The slight downhill grade into the L Eyre depression might be used to generate enough hydro power to run the pumps back at the coast The resulting vast inland sea would certainly change the nearby climate, but how?

 

The greenie in me says leave it alone, human attempts to "improve" nature have usually caused major stuff-ups.

 

...The Bradfield Scheme was an ambitious proposal by Dr John Bradfield in 1938. It would use large pipes, tunnels, pumps and dams to divert water from the monsoon-fed Tully, Herbert and Burdekin rivers into the Thomson River, Queensland...

 

We still have people who believe any water that makes it down our rivers to the ocean is wasted. As if only humans have a right to the water. Any reduction in flood water to the estuaries always hammers the productivity of nearby oceans- what we may pick up in irrigation, we lose in fisheries.

 

 

[facthunter]

It will only affect downwind of the water area. The general drift is roughly South East. Long stretches of a river if fairly straight affect weather  particularly thunderstorm formation. Nev

 

 

[old man emu]

There is no need to build pipelines. An open channel could just as easily carry the water, with tunnels through intervening higher ground. Placing the channel in the Gulf country would be an easier task than diverting Queensland's east coast rivers through the Great Divide. From the vicinity of Burketown to near Camooweal is about 500 kms. That's a long channel, but not impossible. 

 

An alternative would be a 50 km channel from Port Paterson SA to Lake Torrens and another 50 km channel from the northern end of Lake Torrens to the heads of the rivers that flow into Lake Eyre (South). 

 

 

[pmccarthy]

The flow would have to exceed evaporation. It isn't obvious that this is possible for Lake Eyre.

 

 

[pmccarthy]

It is great to learn that Australia is leading the world in per capita renewables.

 

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[old man emu]

The flow would have to exceed evaporation. It isn't obvious that this is possible for Lake Eyre.

 

Don't forget that the inflow from an ocean connection would be continuous. The continuous flow would counteract the high evaporation rate. The annual evaporation rate for the filled Lake Eyre ranges from 1800 to 2000 mm. The evaporation rate from the dry lake floor (excluding the salt crust) is of the order of 170 mm year-1 and the net evaporation rate from the salt-covered surface of Lake Eyre at between 9 and 28 mm year. 

 

Here's some information about Lake Eyre in its present form: http://www.k26.com/eyre/The_Lake/Papers/Lake_Eyre_basics/lake_eyre_basics.html

 

 

[Old Koreelah]

The flow would have to exceed evaporation. It isn't obvious that this is possible for Lake Eyre.

 

If the channel is wide enough, it would. My original idea of pipelines was based on minimising evaporation, but OME seems to be ahead of me and has grasped the idea that lots of evaporation is what we are trying to achieve.

 

 A large water body in central Oz would certainly greatly improve rainfall downwind, particularly in the eastern states.

 

It would probably also change weather patterns in ways we cannot foresee, perhaps for the worse.

 

Some would ask whether this country should make such a massive change to our continent or should we learn to live within the limitations of what nature gave us?

 

Others would say that if we don't develop our resources, someone more powerful will, whether we agree or not.

 

 

[facthunter]

What "nature "gave you is pretty arbitrary unless you see the hand of a higher power in everything. What MAN does is usually to stuff things up. Weeds and plagues of "something " usually intervene. Channels are going to leak and evaporate. Piping is better but 400 kms of pipe make desal about as costly. Cost of pumping).  Trees transpire vast amounts of water, stop salinity and lower ambient temps. Vegetation stops wind type erosion (duststorms)..We have very little topsoil and generally very low incorporated carbon in the soil. Soils are very alkaline in the mallee (old seabed) and acid in  most of the rest.. Acid soils are harder to manage . When the Ph is at either end of the scale  nutrient availability to plants is reduced.. Nev

 

 

[Old Koreelah]

...Channels are going to leak and evaporate. Piping is better but 400 kms of pipe make desal about as costly...

 

Nev I think the whole idea is to increase evaporation over our inland, so a bit more rain might fall.

 

I agree with your concerns about channels leaking, however. The last thing our continent needs is salt water (from the ocean) getting into our groundwater.

 

 

[Bruce]

There is an idea about how reflectors in space could either shade or concentrate sunlight on chosen areas to tip weather systems to our advantage. Remember how a butterfly can trigger a hurricane weeks later?

 

BUT, the legal system would have a field day, with everybody who didn't like the weather suing the reflector operators.

 

Returning to the lake,I would like a good bunch of climate modellers to say what they think would happen if it (lake Eyre) were to be connected to the ocean.  Personally, I don't think it would do much for the rainfall but I like the idea anyway.

 

 

[facthunter]

 Airmass analysis.- tropical maritime- highest water  content still doesn't rain continuously.  Large land masses tend to get semi-permanent highs, which cause dryness  due to subsidence of dry air from higher altitudes, clear skies, frost and outflow  from the centre. Tropical lows  over water are the opposite. moisture laden air is drawn in and rises and cools and condenses releasing heat causing convection high vertical development and lots of water  to go somewhere. You will never get enough water into the inland except by a BIG wet which tends to be self perpetuating to much modify any airmass . THEN you get what we had in OLD  not long before the drought. BIG floods.. Nev

 

 

[old man emu]

Filling Lake Eyre with ocean water would only be reversing what the climatic changes of the past. 35,000 years ago Lake Dieri (or the ancestral Lake Eyre) was 3 times the size of the present Lake Eyre and had a depth of at least 17 m. At that time, lush vegetation surrounded the lake. From 20,000 years on the climate changed so much that the rivers that fed the lakes diminished and then stopped flowing, apart from the occasional flood, and the area became as arid as it is today, the lakes shrinking until only salt lakes remained. It has been estimated that about 125,000 year ago, when Lake Eyre was a deep, permanent megalake of close to 35,000 km2, the combined Lake Eyre-Lake Frome system held 430 km3 of water, compared to about 30 km3 when full in historical time.

 

What should be of more concern to Australians is the occurrence of mega-droughts, which are periods of nearly decade-long drought. There is growing evidence that under warming scenarios of 1.5–3 °C above preindustrial levels, the magnitude and extent of drought, and the occurrence of decade-scale megadrought, is likely to increase across most global land areas, with Australia particularly susceptible.  

 

Recent reconstructions  indicate that 3 major decade-scale drought epochs have occurred in the instrumental record: the 1895 to 1903 “Federation Drought,”(FD) the 1937 to 1945 “World War II Drought,” and the  2000 to 2009 “Millennium Drought” (MD). Rainfall deficiencies during the FD were associated with a sustained period of El Niño activity (the warm mode of the El Niño/Southern Oscillation [ENSO]) combined with the positive phase of the Interdecadal Pacific Oscillation (IPO) and probably neutral to positive values of the Indian Ocean Dipole (IOD).

 

Like ENSO, the IPO is related to the movement of warm water around the Pacific Ocean. Begrudgingly, it shifts its enormous backside around the great Pacific bathtub every 10-30 years, much longer than the 2-7 years of ENSO. The IPO’s pattern is similar to ENSO, which has led climate scientists to think that the two are strongly linked. But the IPO operates on much longer timescales.

 

So, instead of arguing about reducing our carbon footprint, we should be looking to take steps to deal with water supply from rainfall, especially short period periods of low rainfall to megadrought conditions.

 

 

[pmccarthy]

According to Wikipedia, the area of Lake Eyre is 9,500 sq km. So with 2m of annual evaporation it would need 19,000,000 megalitres of flow per year to maintain level. That is just over 52,000 Ml per day needing to come down the channel. At a slope of 1:10,000 as recommended for design of irrigation channels, a 3m wide by 0.5m deep channel delivers 20 Ml per day. I don't know how to scale that up, but it is a factor of 2600 so the channel would have to be roughly 8km wide and 1 km deep!

 

I may have made a mistake here, so would welcome a check on this. Another way to think of this is the Murray river flows about 10,000 Ml per day so it would take five Murray rivers to keep Lake Eyre full. But if we only wanted to keep one fifth of Lake Eyre full then we would only need one Murray River.

 

 

[old man emu]

I don't disagree with the evaporation rate that you quote, but that might be an average figure, higher in summer and less in winter. The trouble is that the figure is today's figure and could change if creating an inland sea, which is what it would be, cooled summer temperatures and reduced evaporation.

 

Mistake or not with your figures, I agree that initially, filling of the lake due to evaporation losses would be slow, but eventually, the amount of water in the lake would exceed the losses due to evaporation. It wouldn't be overnight, it might take a year or two, or maybe five. I'm talking a long term solution here.

 

The channel would have to be a lot deeper than half a metre. The Suez Canal is 24 metres deep, and the Panama is about 12 metres deep. On your figures of a channel with a cross-sectional area of 1.5 metres delivering 20 Ml per day, a channel 10 metres wide by 10 metres deep would deliver {(10 x 10)/1.5 } x 20 Ml = (100/1.5) x 20 = 66.6 x 20 = 133 Ml per day.

 

Also, at the moment, there is no exit from the Lake Eyre Torrens Lake system to the sea, so the water would bank up. The salt levels might be reduces by inflow of rainwater from the existing drainage system.

 

 

[Yenn]

I think we would have difficulty keeping up with the evaporation rate. We would never fill Lake Eyre, but we would get a big pile of salt.

 

Now all we need is a means to get the salt to absorb moisture and then extract the moisture from the salt and use it for irrigation.

 

 

[octave]

It is great to learn that Australia is leading the world in per capita renewables.

 

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Despite Australia's uptake of renewables our standard of living is not rapidly declining as the "renewables alarmist" claim.

 

 

[Old Koreelah]

I think we would have difficulty keeping up with the evaporation rate. We would never fill Lake Eyre...

 

I disagree. The inflow of flood waters thru the Channel Country is usually during the heat of summer, when evaporation losses would be humungous. Despite this, it's been filled a number of times since white fellas arrived.

 

...Now all we need is a means to get the salt to absorb moisture and then extract the moisture from the salt and use it for irrigation.

 

That's pretty much what would happen if we filled the basin with sea water. Solar power would turn it into fresh water for free via evaporation. Much of it is likely to fall as rain on farmland to the east of the lake.

 

 

[Old Koreelah]

According to Wikipedia, the area of Lake Eyre is 9,500 sq km. So with 2m of annual evaporation it would need 19,000,000 megalitres of flow per year to maintain level. That is just over 52,000 Ml per day needing to come down the channel...

 

...and that water all evaporates and most of it travels east, ready to rain over farmland. That's many, many times current irrigation allocations. We'd sure be changing the climate then!

 

 

[facthunter]

2M of evaporation is probably on the low side. the "lake " NE of Mt ISA is 11 M deep and evaporation has made it useless.

 

    The water evaporated  from Lake Eyre won't form cloud till it reaches saturation which might be over the south island of New Zealand. Nev

 

 

[spacesailor]

South Island NZ, that, will do, 

 

It could be SNOW, to fil the glacier,s.

 

Happy greenies now.

 

spacesailor

 

 

[facthunter]

Drought and flood situations are often self perpetuating. Once a low gets established  and the inland gets flooded  the rain can go on essentially forever until the low moves somewhere else.. Tropical Maritime air has lots of water (energy) in it.  Dry conditions also tend to set in until something of consequence changes things over a wide area. Weather patterns follow the movement of the thermal equator  in a north/ south  sense. Summer /winter.  Nev

 

 

[Bruce]

I tried to check the flow figures in this thread, and found a reference to the whole thing . Kotwicki (1986) gives the figure of 18.9 cubic km per year evap from a full lake Eyre. This is in agreement with 9,500 sq km and 2000mm a year.

 

A channel of 40 m wide and 4m deep would have to run at about 4 m/sec to supply this.

 

If this were seawater coming in, it would introduce 25 million tonnes of new salt per year.

 

The committee of met people came to the conclusion that there would not be much effect on rainfall in the inland. You would get sea-breezes around the lake though.

 

I'd do it if I could just for the fun.

 

 

[old man emu]

We have to broaden our field of vision about what creates our climate in Australia.  Concentrating on CO2 levels is tunnel vision. Meteorologists have identified and studied the maritime influences on our climate - the Pacific Oscillation Index, the Indian Ocean Index, the Interdecadal Pacific Oscillation and the Southern Annular Mode. It appears that the Interdecadal Pacific Oscillation (IPO) is the cause of our major droughts and floods.

 

Here's something about the IPO: https://theconversation.com/meet-el-ninos-cranky-uncle-that-could-send-global-warming-into-hyperdrive-72360