Guest essay by Eric Worrall
According to UNSW academic Dr. Clara Stephens, future extreme rainfall will fail to fill Aussie dams, because the drier ground will absorb too much moisture.
What you might not realise about the flow-on effects of climate change
Fri 14 Aug 2020 10.42 AEST
In the coming years, we are likely to see more extreme weather conditions. We will need new engineering approaches to manage the complex impacts on our water resources, writes Dr Clare Stephens.
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Changing rainfall, evaporation and soil
Climate modelling suggests that, in the coming years, average rainfall will decrease over much of the continent. Simultaneously, extreme rainfall is likely to increase, bringing heavier downpours.
Much of the rainfall over Australia is lost to evaporation. The “thirst” of the atmosphere is measured by its evaporative demand. Since the Millennium Droughtbegan in the 1990s, higher temperatures have driven evaporative demand up by increasing the air’s capacity to hold water vapour.
Decreasing annual rainfall and increasing evaporative demand will tend to result in drier soil. Drier soils are more absorbent, so less rain runs directly into waterways. This means that, even if we get heavier downpours in the future, they won’t necessarily produce the floods we rely on to fill dams. Unfortunately, this flood-reducing tendency won’t apply equally to urban environments (where it might actually be helpful) because we have paved over that absorbent soil in cities.
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Read more: https://www.theguardian.com/westpac-scholars-rethink-tomorrow/2020/aug/14/what-you-might-not-realise-about-the-flow-on-effects-of-climate-change
This echoes Tim Flannery’s famous prediction that Aussie dams would never fill again – shorty before record flood years.
Predicting the end of rain is an old game. In the 1920s American hit music hall song “It aint going to rain no mo'”, full of rude verses which poke fun at alarmism, was a worldwide success – not a bad effort in the age before mass media.
2019 was the driest year on record for several regional areas in NSW, with records going back to the late 1800’s. This was on the back of 2 successive years of well below average rainfall. By the time the dry spell started to break early this year, there was virtually no ground cover on most farms, being either eaten by livestock, kangaroos or blown away in dust storms. When it did rain, the result was an incredible amount of water runoff from mediocre even light rainfall events – far more than what is seen with similar falls over wetter periods. The lack of ground cover enabled the water to flow more freely across the earth, quickly finding its way into gully’s and eventually our farm dams. I believe the good Dr Stephens research is incorrect, and appears to be theory rather than observational based.
Torledo it is worth a drive along the Stuart highway to Darwin , along the way you will see huge Mesas , at first you think that the ground must have been lifted up by Vulcanic events until you realize that the ground around them has been eroded away over eons , the amount of soil washed away must be staggering , and this process is still going on today .
As others have mentioned, it is well known in soil science that drier soils are often much more difficult to wet than damp soils. It is one of the reasons that there is often flooding and erosion events if a hard rain comes on the heels of a dry period. When I was taught about this phenomenon so many decades ago, it came under the heading of wetting hysteresis. It often seems the case now that so called researchers have such a narrow area of specialisation that they are ignorant of fundamentals. This also leads to publications in one discipline of phenomena that are commonplace in another.
“researching the performance robustness of hydrologic models under climate change.”
You cannot test the “robustness” of a fantasy !
Another academic sucked into thinking that un-validated climate models create actual real meaningful data.
Sad, really.
She must be a Biden supporter who chooses truth over facts.
Back to ” the truth is what I say it is!”
They get away with this nonsense because Australia is a land of extremes or if you prefer boom and bust , so the individuals that reside in our large cities are easily fooled into believing that when we have a drought that that is the new normal not just part of an ancient pattern that’s been going on for eternity .
Dorothea Mackellar nailed it in 1908 when in her poem ‘My Country’ she wrote that Australia is
‘A land of sweeping plains, Of ragged mountain ranges, Of droughts and flooding rains.’
Droughts and Flooding Rains will be with us long after Dr. Clara Stephens has been lost from memory.
“In the coming years, we are likely to see more extreme weather conditions. ”
Let me guess:
The high-emissions ‘RCP8.5’ global warming scenario
Put this study on the Science Fiction and Fantasy shelf.
It always rains at the end of a drought.
+42
It is called cycles.
I live off grid in Australia. I have been reading about an ongoing drought and falling rainfall for the past few years.
However, not only are my tanks full, they have been close to full for most of this year.
Go for a drive in the country side. There are plenty of dry barren paddocks. However, they are side by side with rich healthy pasture. Too many farmers, overstocking or over cropping say they are in drought, when in fact its really about inappropriate management.
If anything, over thirty five years living in this area, rainfall is slowly increasing. I suspect this lady lives in an office and works on a computer all day. She should get out and see the real world.
You are correct in your observations, Peter, the effects of management are bigger than the effects of weather. One only has to see one well managed property in the middle of ‘droughtstruck’ country to realise this.
Peter D: The trouble is you are talking sense. Anyway you may already know this guy but I saw this on Youtube:
He seems to be managing the natural resources well and by maintaining the water table. I also saw an interesting video on the Aboriginal control of the land with ‘cool’ burning and how they are advising some civil departments. Obviously not everyone is listening as I would have thought knowledge gained over 50,000 years might be worth listening to? What I understood is that the Aboriginals burn in a patch work but ultimately all the land is burnt. That’s probably why Australia has so many plants and trees adapted to fire.
It seems the name of the YouTube was stripped out! It was:
“Natural sequence farming: How Peter Andrews rejuvenates drought-struck land | Australian Story”
I can only imagine she comes from the Joe hairy legs Biden, side of the science debate;
Next!
I imagine Australian weather forecasts on daily tv will inform her of flood risk (surface water runoff) after every hot spell. They do in the UK. Last week we had some flash floods due to this reason.
Dr Clare Stephens looks as though she has lived a full life and gained a lot of experience on the way?
Note: This is sarcasm
And the water vapour feedback? The hydrological cycle is supposed top increase, not decrease.
I have a 100% sure forecast “It will rain” also “it will be sunny”.
At least I thought it would always be sunny sooner or later – but ever since the UK government have been trying to stop people going to the beaches, the forecast has been continual cloud. That is until the day itself arrives, and then magically it turns out to be sunny!
‘Increasing evaporative demand’. Doesn’t that fall as rain somewhere else?
Snow. It’s hard to explain, but the basic hot-makes-cold principle is magic and can only be grasped by PhDs in academia.
Sydney’s main dam, Warrangamba, is now overflowing, despite huge growth in population, and despite Flim Flam Flannery’s prediction of a “perpetual drought” more than a decade ago.
Its a land of drought and flooding rain, and with the approach of a back to back La Nina we can expect seriously big floods next year.
Just some layman thoughts:
“extreme rainfall is likely to increase, bringing heavier downpours”
Looking at historic records for extreme daily rainfall taken by Sydney’s Observatory Hill Park, that go back to 1859, during that time the heaviest downpour measured for a single day was 327.7 millimetres (12.90 inches) on August 6, 1986. That’s some serious Aussie rain.
This is the last 10 years ‘most rainfall in a day’, Sydney:
Inches Millimetres
2.96 March 18, 2019 75.2
4.16 November 28, 2018 105.7
3.35 February 08, 2017 85.1
3.72 April 04, 2016 94.5
4.70 April 21, 2015 119.4
2.79 October 15, 2014 70.9
3.75 January 29, 2013 95.3
4.31 March 08, 2012 109.5
3.91 March 20, 2011 99.3
3.05 February 07, 2010 77.5
These are the numbers back in the 80’s :
9.59 February 03, 1990 243.6
3.13 December 05, 1989 79.5
7.52 January 17, 1988 191.0
4.77 October 25, 1987 121.2
12.90 August 06, 1986 327.7
3.20 October 14, 1985 81.3
9.24 November 09, 1984 234.7
4.31 March 17, 1983 109.5
3.22 September 20, 1982 81.8
2.72 October 20, 1981 69.1
2.58 January 03, 1980 65.5
……and these for the 1950’s, remember, back when we had 25% less CO² in the atmosphere :
5.54 October 22, 1960 140.7
5.30 February 19, 1959 134.6
5.84 February 09, 1958 148.3
3.56 March 29, 1957 90.4
7.56 February 10, 1956 192.0
7.41 May 01, 1955 188.2
4.46 February 22, 1954 113.3
4.14 May 02, 1953 105.2
5.01 July 26, 1952 127.3
4.16 August 01, 1951 105.7
4.70 July 24, 1950 119.4
“Drier soils are more absorbent, so less rain runs directly into waterways.”
A soils infiltration capacity depends on several factors, not least the soils own characteristics of porosity due to high clay or sand content. Compacted soils, crusted soils, recent scorched soils due to wild fires, and the local relief of the land all play a roll in a soils ability to absorbe water.
Any gardener will tell you that after a dry spell, 2 days of continuous light rain will be much more beneficial to the garden than a half hour rain storm for the same quantity of water.
If rainfall occurs at a faster rate than the infiltration capacity runoff will occur, which is generally the case with extreme rainfall events, which apparently are going to become more frequent, which means there will be more runoff water, which means reservoirs need to be made bigger.
Perfect
+10/10
I know everything is upside-down in Australia, but I was unaware PhD stood for Ph… Drongo.
PhD ? What in ? Stupidity ? Simplicity? Ignorance?
Propaganda regurgitation.
And the BoM says there is a good chance of a La Nina and negative IOD going into spring 2020.
“Both La Niña and negative IOD typically increase the chance of above average rainfall across much of Australia during spring.” To go with the recent rainfalls, the farmers will be looking forward to decent grain harvests.
That is, of course, if the BoM is right which is not always the case.
http://www.bom.gov.au/climate/enso/
Meanwhile, back in the real world, just of today Warragamba dam which supplies Sydney’s water, and Flannery said wouldn’t fill again, is 100% full, and spilling over.
It’s full because, as always, it rained a lot earlier in the year, which happens on the east coast of Australia every few years, the water flowed in the creeks, the dam filled up, which is what it does regardless of soil moisture when it rains 300mm in the catchment, which it does every few years, and because the government decided last year to increase the capacity of the desalination plant because academics must have said it wasn’t going to rain again, and the dam continues to completely ignore every academic that says otherwise.
Another PhD who believes his climate models is Dr David Jones.
“IT MAY be time to stop describing south-eastern Australia as gripped by drought and instead accept the extreme dry as permanent, one of the nation’s most senior weather experts warned yesterday.
“Perhaps we should call it our new climate,” said the Bureau of Meteorology’s head of climate analysis, David Jones.” THIS DROUGHT MAY NEVER BREAK, published in the SMH, January 2008.
https://www.smh.com.au/environment/this-drought-may-never-break-20080104-gdrvg6.html
“SMH.” Irony.
It is a very short article, easy to read in a couple of minutes. But in the end she writes the money line:
“Ultimately, however developed the science and however accurate the models become, we need to urgently cut our greenhouse gas emissions and support the rest of the world to do the same.”
Odd how the weasel words evaporate in the presence of propaganda. I think we’ve reached peak academia. Why do we tolerate these numpties and their Lysenkoist nonsense?
This sounds like the warning that was given to Cape Town and the Western Cape.
42 months ago this headline appeared in the Daily Mail:
WATER WARS: Cape Town faces ‘Day Zero’ when the taps will be turned off as South Africa is hit by severe drought
A few weeks later National Geographic published an article:
Why Cape Town Is Running Out of Water, and Who’s Next
A few days later CNN reported:
Day Zero deferred, but Cape Town’s water crisis is far from over
This article quotes a Professor of Geography – who had evidently not lived in the Western Cape – “The situation in Cape Town is almost a foretaste of what is likely to come in cities worldwide”
The Western Cape was proof for alarmists of what was going to happen because of climate change.
What has happened since these alarmist reports? Cape weather!
Today’s readings for the 6 main dams in the Western Cape indicate they are 84% full.
The largest, Theewaterskloof (with over 50% of the total capacity) is at 80.7%
After three good winters – this is a winter rainfall area – and the rainy season has five more weeks to run.
http://www.capetown.gov.za/Family%20and%20home/residential-utility-services/residential-water-and-sanitation-services/this-weeks-dam-levels
I think there is a lesson for this UNSW academic in what is happening in the real world.
” higher temperatures have driven evaporative demand up by increasing the air’s capacity to hold water vapour”
The evaporation rate is actually controlled by relative humidity. For example in Darwin the evaporation rate is usually lower than in Hobart, even though the temperature is significantly higher in Darwin. More importantly, global warming theory (of the variety that she studies) suggests that relative humidity will remain constant as the temperature increases, meaning that evaporation rates would remain constant.