‘It is quite startling’: 4 photos from space that show Australia before and after the recent rain



National Map

Sunanda Creagh, The Conversation

Editor’s note: These before-and-after-images from several sources –NASA’s Worldview application, National Map by Geoscience Australia and Digital Earth Australia – show how the Australian landscape has responded to huge rainfall on the east coast over the last month. We asked academic experts to reflect on the story they tell:


Warragamba Dam, Sydney

Stuart Khan, water systems researcher and professor of civil and environmental engineering.

This map from Digital Earth Australia shows a significant increase in water stored in Lake Burragorang. Lake Burragorang is the name of water body maintained behind the Warragamba Dam wall and the images show mainly the southern source to the lake, which is the Wollondilly River. A short section of the Coxs River source is also visible at the top of the images.

The Warragamba catchment received around 240mm of rain during the second week of February, which produced around 1,000 gigalitres (GL) of runoff to the lake. This took the water storage in the lake from 42% of capacity to more than 80%.

Unlike a typical swimming pool, the lake does not generally have vertical walls. Instead, the river valley runs deeper in the centre and more shallow around the edges. As water storage volumes increase, so does the surface area of water, which is the key feature visible in the images.

Leading up to this intense rainfall event, many smaller events occurred, but failed to produce any significant runoff. The catchment was just too dry. Dry soils act like a sponge and soak up rainfall, rather than allowing it to run off to produce flows in waterways.

The catchment is now in a much wetter state and we can expect to see smaller rainfall events effectively produce further runoff. So water storage levels should be maintained, at least in the short term.

However in the longer term, extended periods of low rainfall and warm temperatures will make this catchment drier.

In the absence of further very intense rainfall events, Sydney will lapse back into drought and diminishing water storages.

This pattern of decreasing storage, broken only by very intense rainfall, can be observed in Sydney’s water storage history.

It is a pattern likely to be exacerbated further in future.


Wivenhoe Dam, Brisbane

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Stuart Khan, water systems researcher and professor of civil and environmental engineering.

Lake Wivenhoe is the body of water maintained behind Wivenhoe Dam wall in southeast Queensland. It is the main water storage for Brisbane as well as much of surrounding southeast Queensland.

This image from National Map shows a visible change in colour from brown to green in the region around the lake. It is quite startling.

This is especially the case to the west of the lake, in mountain range areas such as Toowoomba, Warwick and Stanthorpe. Many of these areas were in very severe drought in January. Stanthorpe officially ran out of water. The February rain has begun to fill many important water storage areas and completely transformed the landscape.

Unfortunately, this part of Australia is highly prone to drought and we can expect to see this pattern recur over coming decades.

Much climate science research indicates more extreme weather events in future. That means more extreme high temperatures, more intense droughts and more severe wet weather.

There are many challenges ahead for Australian water managers as they seek to overcome the inevitable booms and busts of future water availability.




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Australia-wide

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Grant Williamson, Research Fellow in Environmental Science, University of Tasmania

It’s clear from this map above, from NASA Worldview, the monsoon has finally arrived in northern Australia and there’s been quite a lot of rain.

On the whole, you can see how rapidly the Australian environment can respond to significant rainfall events.

It’s important to remember that most of that greening up will be the growth of grasses, which respond more rapidly after rain.

The forests that burned will not be responding that quickly. The recovery process will be ongoing and within six months to a year you’d expect to see significant regrowth in the eucalyptus forests.

Other more fire-sensitive vegetation, like rainforests, may not exhibit the same sort of recovery.




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Grant Williamson, Research Fellow in Environmental Science, University of Tasmania

This slider from National Map shows both fire impact, and greening up after rain.

On the left – an area west of Cooma on December 24 – you can see the yellow treeless areas, indicating the extent of the drought, and the dark green forest vegetation. This image also shows quite a lot of smoke, as you’d expect.

On the right – the area on February 22 – a lot of those yellow areas are now significantly greener after the rain. However, some of those dark green forest areas are now brown or red, where they have been burnt.

It’s clear there is a long road ahead for recovery of these forests that were so badly burned in the recent fires but they will start resprouting in the coming months.

Grant Williamson is a Tasmania-based researcher with the NSW Bushfire Risk Management Research Hub.The Conversation


Sunanda Creagh, Head of Digital Storytelling, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We won’t have fusion generators in five years. But the holy grail of clean energy may still be on its way



CCFE / JET

Matthew Hole, Australian National University

Recent reports from scientists pursuing a new kind of nuclear fusion technology are encouraging, but we are still some distance away from the “holy grail of clean energy”.

The technology developed by Heinrich Hora and his colleagues at the University of NSW uses powerful lasers to fuse together hydrogen and boron atoms, releasing high-energy particles that can be used to generate electricity. As with other kinds of nuclear fusion technology, however, the difficulty is in building a machine that can reliably initiate the reaction and harness the energy it produces.

What is fusion?

Fusion is the process that powers the Sun and the stars. It occurs when the nuclei of two atoms are forced so close to one another that they combine into one, releasing energy in the process. If the reaction can be tamed in the laboratory, it has the potential to deliver near-limitless baseload electricity with virtually zero carbon emissions.

The easiest reaction to initiate in the laboratory is the fusion of two different isotopes of hydrogen: deuterium and tritium. The product of the reaction is a helium ion and a fast-moving neutron. Most fusion research to date has pursued this reaction.

Deuterium-tritium fusion works best at a temperature of about 100,000,000℃. Confining a plasma – the name for the flamelike state of matter at such temperatures – that hot is no mean feat.




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The leading approach to harnessing fusion power is called toroidal magnetic confinement. Superconducting coils are used to create a field about a million times stronger than Earth’s magnetic field to contain the plasma.

Scientists have already achieved deuterium-tritium fusion at experiments in the US (the Tokamak Fusion Test Reactor) and the UK (the Joint European Torus). Indeed, a deuterium-tritium fusion campaign will happen in the UK experiment this year.

These experiments initiate a fusion reaction using massive external heating, and it takes more energy to sustain the reaction than the reaction produces itself.

The next phase of mainstream fusion research will involve an experiment called ITER (“the way” in Latin) being built in the south of France. At ITER, the confined helium ions created by the reaction will produce as much heating as the external heating sources. As the fast neutron carries four times as much energy as the helium ion, the power gain is a factor of five.

ITER is a proof of concept before the construction of a demonstration power plant.

What’s different about using hydrogen and boron?

The technology reported by Hora and colleagues suggests using a laser to create a very strong confining magnetic field, and a second laser to heat a hydrogen-boron fuel pellet to reach the point of fusion ignition.

When a hydrogen nucleus (a single proton) fuses with a boron-11 nucleus, it produces three energetic helium nuclei. Compared with the deuterium-tritium reaction, this has the advantage of not producing any neutrons, which are hard to contain.

However, the hydrogen-boron reaction is much more difficult to trigger in the first place. Hora’s solution is to use a laser to heat a small fuel pellet to ignition temperature, and another laser to heat up metal coils to create a magnetic field that will contain the plasma.

The technology uses very brief laser pulses, lasting only nanoseconds. The magnetic field required would be extremely strong, about 1,000 times as strong as the one used in deuterium-tritium experiments. Researchers in Japan have already used this technology to create a weaker magnetic field.

Hora and colleagues claim their process will create an “avalanche effect” in the fuel pellet that means a lot more fusion will occur than would otherwise be expected. While there is experimental evidence to support some increase in fusion reaction rate by tailoring laser beam and target, to compare with deuterium-tritium reactions the avalanche effect would need to increase the fusion reaction rate by more than 100,000 times at 100,000,000℃. There is no experimental evidence for an increase of this magnitude.




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Where to from here?

The experiments with hydrogen and boron have certainly produced fascinating physical results, but projections by Hora and colleagues of a five-year path to realising fusion power seem premature. Others have attempted laser-triggered fusion. The National Ignition Facility in the US, for example, has attempted to achieve hydrogen-deuterium fusion ignition using 192 laser beams focused on a small target.

These experiments reached one-third of the conditions needed for ignition for a single experiment. The challenges include precise placement of the target, non-uniformity of the laser beam, and instabilities that occur as the target implodes.
These experiments were conducted at most twice per day. By contrast, estimates suggest that a power plant would require the equivalent of 10 experiments per second.

The development of fusion energy is most likely to be realised by the mainstream international program, with the ITER experiment at its core. Australia has international engagement with the ITER project in fields of theory and modelling, materials science and technology development.

Much of this is based at the ANU in collaboration with Australian Nuclear Science and Technology Organisation, which is the signatory to a cooperation agreement with ITER. That said, there is always room for smart innovation and new concepts, and it is wonderful to see all kinds of investment in fusion science.The Conversation

Matthew Hole, Senior Research Fellow, Mathematical Sciences Institute, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.