Extreme heat and rain: thousands of weather stations show there’s now more of both, for longer



ChameleonsEye/Shutterstock

Jim Salinger, University of Tasmania and Lisa Alexander, UNSW

A major global update based on data from more than 36,000 weather stations around the world confirms that, as the planet continues to warm, extreme weather events such as heatwaves and heavy rainfall are now more frequent, more intense, and longer.

The research is based on a dataset known as HadEX and analyses 29 indices of weather extremes, including the number of days above 25℃ or below 0℃, and consecutive dry days with less than 1mm of rain. This latest update compares the three decades between 1981 and 2010 to the 30 years prior, between 1951 and 1980.

Globally, the clearest index shows an increase in the number of above-average warm days.


Author provided

For Australia, the team found a country-wide increase in warm temperature extremes and heatwaves and a decrease in cold temperature extremes such as the coldest nights. Broadly speaking, rainfall extremes have increased in the west and decreased in the east, but trends vary by season.

In New Zealand, temperate regions experience significantly more summer days and northern parts of the country are now frost-free.




Read more:
The world endured 2 extra heatwave days per decade since 1950 – but the worst is yet to come


Extreme temperatures

Unusually warm days are becoming more common throughout Australia. When we compare 1981-2010 with 1951-80, the increase is substantial: more than 20 days per year in the far north of Australia, and at least 10 days per year in most areas apart from the south coast. The increase occurs in all seasons but is largest in spring.

This increase in temperature extremes can have devastating impacts for human health, particularly for older people and those with pre-existing medical conditions. Excessive heat is not only an issue for people living in cities but also for rural communities that have already been exposed to days with temperatures above 50℃.

New Zealanders are also experiencing more days with temperatures of 25℃ or more. The climate stations show the frequency of unusually warm days has increased from 8% to 12% from 1950 to 2018, with an average of 19 to 24 days a year above 25℃ across the country. Unusually warm days, defined as days in the top 10% of historic records for the time of year, are also becoming more common in both countries.

During the summers of 2017-18 and 2018-19, marine heatwaves delivered 32 and 26 (respectively) days above 25℃ nationwide in New Zealand, well above the average of 20 days. This led to accelerated glacial melting in the Southern Alps and major disruption to marine ecosystems, with die-offs of bull kelp around the South Island coast and salmon in aquaculture farms in the Marlborough Sounds.




Read more:
Farmed fish dying, grape harvest weeks early – just some of the effects of last summer’s heatwave in NZ


More heat, more rain, less frost

In many parts of New Zealand, cold extremes are changing faster than warm extremes.

Between 1950 and 2018, frost days (days below 0℃) have declined across New Zealand, particularly in northern parts of the country which has now become frost-free, enabling farmers to grow subtropical pasture grasses. At the same time, crops that require winter frosts to set fruit are no longer successful, or can only be grown with chemical treatments (currently under review) that simulate winter chilling.

Across New Zealand, the heat available for crop growth during the growing season is increasing, which means wine growers have to shift varieties further south.

In Australia, the situation is more complicated. In many parts of northern and eastern Australia, there has also been a large decrease in the number of cold nights. But in parts of southeast and southwest Australia, frost frequency has stabilised, or even increased in places, since the 1980s.

These areas have seen a large decrease in winter rainfall in recent decades. The higher number of dry, clear nights in winter, favourable for frost formation, has cancelled out the broader warming trend.




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In Australia, extreme rainfall has become more frequent in many parts of northern and western Australia, especially the northwest, which has become wetter since the 1960s. In eastern and southern Australia the picture is more mixed, with little change in the number of days with 10mm or more of rain, even in those regions where total rainfall has declined.

In New Zealand, more extremely wet days contribute towards the annual rainfall total in the east of the North Island, with a smaller increase in the west and south of the South Island. For Australia, there are significant drying trends in parts of the southwest and northeast, but little change elsewhere.

Extremes of temperature and precipitation can have dramatic effects, as seen during two marine heatwaves in New Zealand and the hottest, driest year in Australia during 2019.The Conversation

Jim Salinger, Honorary Associate, Tasmanian Institute for Agriculture, University of Tasmania and Lisa Alexander, Chief Investigator ARC Centre of Excellence for Climate System Science and Associate Professor Climate Change Research Centre, UNSW

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

The world endured 2 extra heatwave days per decade since 1950 – but the worst is yet to come



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Sarah Perkins-Kirkpatrick, UNSW

The term “heatwave” is no stranger to Australians. Defined as when conditions are excessively hot for at least three days in a row, these extreme temperature events have always punctuated our climate.

With many of us in the thick of winter dreaming of warmer days, it’s important to remember how damaging heatwaves can be.

In 2009, the heatwave that preceded Black Saturday killed 374 people. The economic impact on Australia’s workforce from heatwaves is US$6.2 billion a year (almost AU$9 billion). And just last summer, extreme temperature records tumbled, contributing to Australia’s unprecedented bushfire season.

What are heatwaves?

Our new study – the first worldwide assessment of heatwaves at the regional scale – found heatwaves have become longer and more frequent since 1950. And worryingly, we found this trend has accelerated.

We also examined a new metric: “cumulative heat”. This measures how much extra heat a heatwave can contribute, and the new perspective is eye-opening.

What is ‘extra heat’?

In southeast Australia’s worst heatwave season in 2009, we endured an extra heat of 80℃. Let’s explore what that means.

For a day to qualify as being part of a heatwave, a recorded temperature should exceed an officially declared “heatwave threshold”.

And cumulative heat is generally when the temperature above that threshold across all heatwave days are added up.

Let’s say, for example, a particular location had a heatwave threshold of around 30℃. The “extra heat” on a day where temperatures reach 35℃ would be 5℃. If the heatwave lasted for three days, and all days reached 35℃, then the cumulative heat for that event would be 15℃.

Another decade, another heatwave day

We found almost every global region has experienced a significant increase in heatwave frequency since 1950. For example, southern Australia has experienced, on average, one extra heatwave day per decade since 1950.




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However, other regions have experienced much more rapid increases. The Mediterranean has seen approximately 2.5 more heatwave days per decade, while the Amazon rainforest has seen an extra 5.5 more heatwave days per decade since 1950.

The global average sits at approximately two extra heatwave days per decade.

The last 20 years saw the worst heatwave seasons

Since the 1950s, almost all regions experienced significant increases in the extra heat generated by heatwaves.

Over northern and southern Australia, the excess heat from heatwaves has increased by 2-3℃ per decade. This is similar to other regions, such as western North America, the Amazon and the global average.

Alaska, Brazil and West Asia, however, have cumulative heat trends of a massive 4-5℃ per decade. And, for the vast majority of the world, the worst seasons occurred in the last 20 years.

In the heatwave before Black Saturday, 374 people died.
Shutterstock

We also examined whether heatwaves were changing at a constant rate, or were speeding up or slowing down. With the exception of average intensity, we found heatwave trends have not only increased, but have accelerated since the 1950s.

Don’t be fooled by the maths

Interestingly, average heatwave intensity showed little – if any – changes since 1950. But before we all breathe a sigh of relief, this is not because climate change has stopped, or because heatwaves aren’t getting any warmer. It’s the result of a mathematical quirk.




Read more:
Climate change: 40°C summer temperatures could be common in UK by 2100


Since we’re seeing more heatwaves – which we found are also generally getting longer – there are more days to underpin the average intensity. While all heatwave days must exceed a relative extreme threshold, some days will exceed this threshold to a lesser extent than others. This brings the overall average down.

When we look at changes in cumulative heat, however, there’s just no denying it. Extra heat – not the average – experienced in almost all regions, is what can have adverse impacts on our health, infrastructure and ecosystems.

The Amazon has endured 5.5 more heatwave days per decade since 1950.
Shutterstock

Like nothing we’ve experienced before

While the devastating impacts of heatwaves are clear, it has been difficult to consistently measure changes in heatwaves across the globe. Previous studies have assessed regional heatwave trends, but data constraints and the spectrum of different heatwave metrics available have made it hard to compare regional changes in heatwaves.

Our study has closed this gap, and clearly shows heatwaves are on the rise. We are seeing more of them and they are generating more heat at an increasing pace.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


While Australia may be no stranger to heatwaves in the past, those we see in the future under these accelerating trends will certainly be foreign.

For example, a 2014 study found that depending on where you are in Australia, anywhere between 15 and 50 extra heatwave days will occur by 2100 compared to the second half of the 20th century.

We can still abate those trends if we work collectively, effectively and urgently to reduce our greenhouse gas emissions.The Conversation

Sarah Perkins-Kirkpatrick, ARC Future Fellow, UNSW

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

How drought-breaking rains transformed these critically endangered woodlands into a flower-filled vista



Wildflowers blooming in box gum grassy woodland
Jacqui Stol, Author provided

Jacqui Stol, CSIRO; Annie Kelly, and Suzanne Prober, CSIRO

In box gum grassy woodlands, widely spaced eucalypts tower over carpets of wildflowers, lush native grasses and groves of flowering wattles. It’s no wonder some early landscape paintings depicting Australian farm life are inspired by this ecosystem.

But box gum grassy woodlands are critically endangered. These woodlands grow on highly productive agricultural country, from southern Queensland, along inland slopes and tablelands, into Victoria.

Many are degraded or cleared for farming. As a result, less than 5% of the woodlands remain in good condition. What remains often grows on private land such as farms, and public lands such as cemeteries or travelling stock routes.




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Very little is protected in public conservation reserves. And the recent drought and record breaking heat caused these woodlands to stop growing and flowering.

But after Queensland’s recent drought-breaking rain earlier this year, we surveyed private farmland and found many dried-out woodlands in the northernmost areas transformed into flower-filled, park-like landscapes.

And landholders even came across rarely seen marsupials, such as the southern spotted-tail quoll.

Native yellow wildflowers called ‘scaly buttons’ bloom on a stewardship site.
Jacqui Stol, Author provided

Huge increase in plant diversity

These surveys were part of the Australian government’s Environmental Stewardship Program, a long-term cooperative conservation model with private landholders. It started in 2007 and will run for 19 years.

We found huge increases in previously declining native wildflowers and grasses on the private farmland. Many trees assumed to be dying began resprouting, such as McKie’s stringybark (Eucalyptus mckieana), which is listed as a vulnerable species.

This newfound plant diversity is the result of seeds and tubers (underground storage organs providing energy and nutrients for regrowth) lying dormant in the soil after wildflowers bloomed in earlier seasons. The dormant seeds and tubers were ready to spring into life with the right seasonal conditions.

For example, Queensland Herbarium surveys early last year, during the drought, looked at a 20 metre by 20 metre plot and found only six native grass and wildflower species on one property. After this year’s rain, we found 59 species in the same plot, including many species of perennial grass (three species jumped to 20 species post rain), native bluebells and many species of native daisies.




Read more:
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On another property with only 11 recorded species, more than 60 species sprouted after the extensive rains.

In areas where grazing and farming continued as normal (the paired “control” sites), the plots had only around half the number of plant species as areas managed for conservation.

Spotting rare marsupials

Landowners also reported several unusual sightings of animals on their farms after the rains. Stewardship program surveyors later identified them as two species of rare and endangered native carnivorous marsupials: the southern spotted-tailed quoll (mainland Australia’s largest carnivorous marsupial) and the brush-tailed phascogale.

The population status of both these species in southern Queensland is unknown. The brush-tailed phascogale is elusive and rarely detected, while the southern spotted-tailed quolls are listed as endangered under federal legislation.

Until those sightings, there were no recent records of southern spotted-tailed quolls in the local area.

A spotted tailed quoll caught in a camera trap.
Sean Fitzgibbon, Author provided

These unusual wildlife sightings are valuable for monitoring and evaluation. They tell us what’s thriving, declining or surviving, compared to the first surveys for the stewardship program ten years ago.

Sightings are also a promising signal for the improving condition of the property and its surrounding landscape.

Changing farm habits

More than 200 farmers signed up to the stewardship program for the conservation and management of nationally threatened ecological communities on private lands. Most have said they’re keen to continue the partnership.

The landholders are funded to manage their farms as part of the stewardship program in ways that will help the woodlands recover, and help reverse declines in biodiversity.

For example, by changing the number of livestock grazing at any one time, and shortening their grazing time, many of the grazing-sensitive wildflowers have a better chance to germinate, grow, flower and produce seeds in the right seasonal conditions.




Read more:
‘Plant blindness’ is obscuring the extinction crisis for non-animal species


They can also manage weeds, and not remove fallen timber or loose rocks (bushrock). Fallen timber and rocks protect grazing-sensitive plants and provide habitat for birds, reptiles and invertebrates foraging on the ground.

Cautious optimism

So can we be optimistic for the future of wildlife and wildflowers of the box gum grassy woodlands? Yes, cautiously so.

Landholders are learning more about how best to manage biodiversity on their farms, but ecological recovery can take time. In any case, we’ve discovered how resilient our flora and fauna can be in the face of severe drought when given the opportunity to grow and flourish.

The rare hooded robin has also been recorded on stewardship sites during surveys.
Micah Davies, Author provided

Climate change is bringing more extreme weather events. Last year was the warmest on record and the nation has been gripped by severe, protracted drought. There’s only so much pressure our iconic wildlife and wildflowers can take before they cross ecological thresholds that are difficult to bounce back from.

More government programs like this, and greater understanding and collaboration between scientists and farmers, create a tremendous opportunity to keep changing that trajectory for the better.The Conversation

Jacqui Stol, Senior Experimental Scientist, Ecologist, CSIRO Land and Water, CSIRO; Annie Kelly, Senior Ecologist, and Suzanne Prober, Senior Principal Research Scientist, CSIRO

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

We dug up Australian weather records back to 1838 and found snow is falling less often



State Library of South Australia

Joelle Gergis, Australian National University and Linden Ashcroft, University of Melbourne

As we slowly emerge from lockdown, local adventures are high on people’s wish lists. You may be planning a trip to the ski fields, or even the nearby hills to revel in the white stuff that occasionally falls around our southern cities after an icy winter blast.

Our new research explores these low-elevation snowfall events. We pieced together weather records back to 1838 to create Australia’s longest analysis of daily temperature extremes and their impacts on society.

These historical records can tell us a lot about Australia’s pre-industrial climate, before the large-scale burning of fossil fuels tainted global temperature records.

They also help provide a longer context to evaluate more recent temperature extremes.

We found snow was once a regular feature of the southern Australian climate. But as Australia continues to warm under climate change, cold extremes are becoming less frequent and heatwaves more common.

Heatwaves in Adelaide are becoming more common.
David Mariuz/AAP

Extending Australia’s climate record

Data used by the Bureau of Meteorology to study long-term weather and climate dates back to the early 1900s. This is when good coverage of weather stations across the country began, and observations were taken in a standard way.

But many older weather records exist in national and state archives and libraries, as well as local historical societies around the country.




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We analysed daily weather records from the coastal city of Adelaide and surrounding areas, including the Adelaide Hills, back to 1838. Adelaide is the Australian city worst affected by heatwaves, and the capital of our nation’s driest state, South Australia.

To crosscheck the heatwaves and cold extremes identified in our historical temperature observations, we also looked at newspaper accounts, model simulations of past weather patterns, and palaeoclimate records.

The agreement was remarkable. It demonstrates the value of historical records for improving our estimation of future climate change risk.

Weather journal of Adelaide’s historical climate held by the National Archives of Australia.
National Archives of Australia

‘Limpness to all mankind’

While most other historical climate studies have looked at annual or monthly values, the new record enabled us to look at daily extremes.

This is important, because global temperature increases are most clearly detected in changes to extreme events such as heatwaves. Although these events may only last a few days, they have very real impacts on human health, agriculture and infrastructure.

Our analysis focused on the previously undescribed period before 1910, to extend the Bureau of Meteorology’s official record as far as possible.

Using temperature observations, we identified 34 historical heatwaves and 81 cold events in Adelaide from 1838–1910. We found more than twice as many of these “snow days” by conducting an independent analysis of snowfall accounts in historical documents.

Almost all the events in the temperature observations were supported by newspaper reports. This demonstrated our method can accurately identify historical temperature extremes.

For example, an outbreak of cold air on June 22, 1908, delivered widespread snow across the hills surrounding Adelaide. The Express and Telegraph newspaper reported:

Many people made a special journey from Adelaide by train, carriage, or motor to revel in the unwonted delight of gazing on such a wide expanse of real snow, and all who did so felt that their trouble was amply rewarded by the panorama of loveliness spread out before their enraptured eyes.

Snowballing at Mount Lofty 29 August 1905.
Source: State Library of South Australia

From December 26-30, 1897, Adelaide was gripped by a heatwave that produced five days above 40℃. Newspapers reported heat-related deaths, agricultural damage, animals dying in the zoo, bushfires and even “burning hot pavements scorching the soles of people’s shoes”. As The Advertiser reported:

When the mercury reaches its “century” (100℉ or 37.6℃) there must be a really uncomfortable experience for everyone. One such day can be struggled with; but six of them in a fortnight, three in succession — that is a thing to bring limpness to all mankind.

On December 31, 1897, the South Australian Register wrote prophetically of future Australian summers:

May Heaven preserve us from being here when the “scorchers” try and add a few degrees to the total.

Newspaper account of a deadly heatwave published in the South Australian Register on Friday 31 December 1897.
National Library of Australia

A longer view

While Australia has a long history of hot and cold extremes, our extended analysis shows that their frequency and intensity is changing.

The quality of the very early part of the record is still uncertain, so the information from the 1830s and 1840s must be treated with caution. That said, there is excellent agreement with newspaper and other historical records.

Our research suggests low-elevation snow events around Adelaide have become less common over the past 180 years. This can be seen in both temperature observations and independent newspaper accounts. For example, snowfall was exceptionally high in the 1900s and 1910s — more than four times more frequent than other decades.




Read more:
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We also found heatwaves are becoming more frequent in Adelaide. The decade 2010–19 has the highest count of heatwaves of any decade in the record. Although recent heatwaves are not significantly longer than those of the past, our analysis showed heatwaves of up to ten days are possible.

Previous Australian studies have identified an increase in extreme heat and a corresponding decrease in cold events. However, this is the longest analysis in Australia, and the first to systematically combine instrumental and documentary information.

Number of heatwaves identified in Adelaide from January 1838 to August 2019. No digitised temperature observations are available from 1 January 1848 – 1 November 1856, so these decades are shown in lighter shades.
Author supplied
Number of extreme cold days identified in Adelaide from January 1838 to August 2019. No digitised temperature observations are currently available from 1 January 1848 – 1 November 1856, so these decades are shaded grey.
Author supplied

Learning from the past

This study shows we can use historical weather records to get a better picture of Australia’s long-term weather and climate history. By using different sources of information, we can piece together the significant events in our climate history with greater certainty.

Historical records tell us about more than just exciting day trips of the past. They also hold the key to understanding impacts of extreme events, such as heat-related deaths or agricultural damage, in the future.

A better understanding of these pre-industrial extremes will help emergency management services better adapt to increased climate risk, as Australia continues to warm.




Read more:
Just how hot will it get this century? Latest climate models suggest it could be worse than we thought


The Conversation


Joelle Gergis, Senior Lecturer in Climate Science, Australian National University and Linden Ashcroft, Lecturer in climate science and science communication, University of Melbourne

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

Australia, it’s time to talk about our water emergency



Dean Lewins/AAP

Quentin Grafton, Crawford School of Public Policy, Australian National University; Matthew Colloff, Australian National University; Paul Wyrwoll, Australian National University, and Virginia Marshall, Australian National University

The last bushfire season showed Australians they can no longer pretend climate change will not affect them. But there’s another climate change influence we must also face up to: increasingly scarce water on our continent.

Under climate change, rainfall will become more unpredictable. Extreme weather events such as cyclones will be more intense. This will challenge water managers already struggling to respond to Australia’s natural boom and bust of droughts and floods.

Thirty years since Australia’s water reform project began, it’s clear our efforts have largely failed. Drought-stricken rural towns have literally run out of water. Despite the recent rains, the Murray Darling river system is being run dry and struggles to support the communities that depend on it.

We must find another way. So let’s start the conversation.

It’s time for a new national discussion about water policy.
Joe Castro/AAP

How did we get here?

Sadly, inequitable water outcomes in Australia are not new.

The first water “reform” occurred when European settlers acquired water sources from First Peoples without consent or compensation. Overlaying this dispossession, British common law gave new settlers land access rights to freshwater. These later converted into state-owned rights, and are now allocated as privately held water entitlements.

Some 200 years later, the first steps towards long-term water reform arguably began in the 1990s. The process accelerated during the Millennium Drought and in 2004 led to the National Water Initiative, an intergovernmental water agreement. This was followed in 2007 by a federal Water Act, upending exclusive state jurisdiction over water.




Read more:
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Under the National Water Initiative, state and territory water plans were to be verified through water accounting to ensure “adequate measurement, monitoring and reporting systems” across the country.

This would have boosted public and investor confidence in the amount of water being traded, extracted and recovered – both for the environment and the public good.

This vision has not been realised. Instead, a narrow view now dominates in which water is valuable only when extracted, and water reform is about subsidising water infrastructure such as dams, to enable this extraction.

The National Water Initiative has failed.
Dean Lewins/AAP

Why we should all care

In the current drought, rural towns have literally run out of fresh drinking water. These towns are not just dots on a map. They are communities whose very existence is now threatened.

In some small towns, drinking water can taste unpleasant or contain high levels of nitrate, threatening the health of babies. Drinking water in some remote Indigenous communities is not always treated, and the quality rarely checked.

In the Murray-Darling Basin, poor management and low rainfall have caused dry rivers, mass fish kills, and distress in Aboriginal communities. Key aspects of the basin plan have not been implemented. This, coupled with bushfire damage, has caused long-term ecological harm.

How do we fix the water emergency?

Rivers, lakes and wetlands must have enough water at the right time. Only then will the needs of humans and the environment be met equitably – including access to and use of water by First Peoples.

Water for the environment and water for irrigation is not a zero-sum trade-off. Without healthy rivers, irrigation farming and rural communities cannot survive.

A national conversation on water reform is needed. It should recognise and include First Peoples’ values and knowledge of land, water and fire.

Our water brief, Water Reform For All,
proposes six principles to build a national water dialogue:

  1. establish shared visions and goals
  2. develop clarity of roles and responsibilities
  3. implement adaptation as a way to respond to an escalation of stresses, including climate change and governance failures
  4. invest in advanced technology to monitor, predict and understand changes in water availability
  5. integrate bottom-up and community-based adaptation, including from Indigenous communities, into improved water governance arrangements
  6. undertake policy experiments to test new ways of managing water for all
The Darling River is in poor health.
Dean Lewins/AAP

Ask the right questions

As researchers, we don’t have all the answers on how to create a sustainable, equitable water future. No-one does. But in any national conversation, we believe these fundamental questions must be asked:

  1. who is responsible for water governance? How do decisions and actions of one group affect access and availability of water for others?

  2. what volumes of water are extracted from surface and groundwater systems? Where, when, by whom and for what?

  3. what can we predict about a future climate and other long-term drivers of change?

  4. how can we better understand and measure the multiple values that water holds for communities and society?

  5. where do our visions for the future of water align? Where do they differ?

  6. what principles, protocols and processes will help deliver the water reform needed?

  7. how do existing rules and institutions constrain, or enable, efforts to achieve a shared vision of a sustainable water future?

  8. how do we integrate new knowledge, such as water availability under climate change, into our goals?

  9. what restitution is needed in relation to water and Country for First Peoples?

  10. what economic sectors and processes would be better suited to a water-scarce future, and how might we foster them?

Water reform for all

These questions, if part of a national conversation, would reinvigorate the water debate and help put Australia on track to a sustainable water future.

Now is the time to start the discussion. Long-accepted policy approaches in support of sustainable water futures are in question. In the Murray-Darling Basin, some states even question the value of catchment-wide management. The formula for water-sharing between states is under attack.




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Even science that previously underpinned water reform is being questioned

We must return to basics, reassess what’s sensible and feasible, and debate new ways forward.

We are not naive. All of us have been involved in water reform and some of us, like many others, suffer from reform fatigue.

But without a fresh debate, Australia’s water emergency will only get worse. Reform can – and must – happen, for the benefit of all Australians.


The following contributed to this piece and co-authored the report on which it was based: Daniel Connell, Katherine Daniell, Joseph Guillaume, Lorrae van Kerkoff, Aparna Lal, Ehsan Nabavi, Jamie Pittock, Katherine Taylor, Paul Tregoning, and John WilliamsThe Conversation

Quentin Grafton, Director of the Centre for Water Economics, Environment and Policy, Crawford School of Public Policy, Australian National University; Matthew Colloff, Honorary Senior Lecturer, Australian National University; Paul Wyrwoll, Research fellow, Australian National University, and Virginia Marshall, Inaugural Indigenous Postdoctoral Fellow, Australian National University

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

A rare natural phenomenon brings severe drought to Australia. Climate change is making it more common



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Nicky Wright, Australian National University; Bethany Ellis, Australian National University, and Nerilie Abram, Australian National University

Weather-wise, 2019 was a crazy way to end a decade. Fires spread through much of southeast Australia, fuelled by dry vegetation from the ongoing drought and fanned by hot, windy fire weather.

On the other side of the Indian Ocean, torrential rainfall and flooding devastated parts of eastern Africa. Communities there now face a locust plague and food shortages.

These intense events can partly be blamed on the extreme positive Indian Ocean Dipole, a climate phenomenon that unfolded in the second half of 2019.




Read more:
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The Indian Ocean Dipole refers to the difference in sea surface temperature on either side of the Indian Ocean, which alters rainfall patterns in Australia and other nations in the region. The dipole is a lesser-known relative of the Pacific Ocean’s El Niño.

Climate drivers, such as the Indian Ocean Dipole, are an entirely natural phenomenon, but climate change is modifying the behaviour of these climate modes.

In research published today in Nature, we reconstructed Indian Ocean Dipole variability over the last millennium. We found “extreme positive” Indian Ocean Dipole events like last year’s are historically very rare, but becoming more common due to human-caused climate change. This is big news for a planet already struggling to contain global warming.

So what does this new side-effect of climate change mean for the future?

The Indian Ocean brings drought and flooding rain

First, let’s explore what a “positive” and “negative” Indian Ocean Dipole means.

During a “positive” Indian Ocean Dipole event, waters in the eastern Indian Ocean become cooler than normal, while waters in the western Indian Ocean become warmer than normal.

Warmer water causes rising warm, moist air, bringing intense rainfall and flooding to east Africa. At the same time, atmospheric moisture is reduced over the cool waters of the eastern Indian Ocean. This turns off one of Australia’s important rainfall sources.




Read more:
Dipole: the ‘Indian Niño’ that has brought devastating drought to East Africa


In fact, over the past century, positive Indian Ocean Dipoles have led to the worst droughts and bushfires in southeast Australia.

The Indian Ocean Dipole also has a negative phase, which is important to bring drought-breaking rain to Australia. But the positive phase is much stronger and has more intense climate impacts.

We’ve experienced extreme positive Indian Ocean Dipole events before. Reliable instrumental records of the phenomenon began in 1958, and since then a string of very strong positive Indian Ocean Dipoles have occurred in 1961, 1994, 1997 and now 2019.

The Dipole Mode Index is used to track variability of the Indian Ocean Dipole.
Author provided

But this instrumental record is very short, and it’s tainted by the external influence of climate change.

This means it’s impossible to tell from instrumental records alone how extreme Indian Ocean Dipoles can be, and whether human-caused climate change is influencing the phenomenon.

Diving into the past with corals

To uncover just how the Indian Ocean Dipole has changed, we looked back through the last millennium using natural records: “cores” taken from nine coral skeletons (one modern, eight fossilised).

These coral samples were collected just off of Sumatra, Indonesia, so they’re perfectly located for us to reconstruct the distinct ocean cooling that characterises positive Indian Ocean Dipole events.

Scientists drilling into corals to study past climate. Corals are like trees, and grow a band for every year they live.
Jason Turl, Author provided

Corals grow a lot like trees. For every year they live they produce a growth band, and individual corals can live for more than 100 years. Measuring the oxygen in these growth bands gives us a detailed history of the water temperature the coral grew in, and the amount of rainfall over the reef.

In other words, the signature of extreme events like past positive Indian Ocean Dipoles is written in the coral skeleton.

Altogether, our coral-based reconstruction of the Indian Ocean Dipole spans 500 years between 1240 and 2019. There are gaps in the timeline, but we have the best picture so far of how exactly the Indian Ocean Dipole has varied in the past.

How unusual was the 2019 Indian Ocean Dipole event?

Extreme events like the 2019 Indian Ocean Dipole have historically been very rare.

We found only ten extreme positive Indian Ocean Dipole events in the entire record. Four occurred in the past 60 years, but only six occurred in the remaining 440 years before then. This adds more weight to evidence that positive Indian Ocean Dipole events have been occurring more often in recent decades, and becoming more intense.




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But another finding from the reconstruction surprised – and worried – us. Events like 2019 aren’t the worst of what the Indian Ocean Dipole can throw at us.

Of the extreme events we found in our reconstruction, one of them, in 1675, was much stronger than anything we’ve seen in observations from the last 60 years.

The 1675 event was around 30–40% stronger than what we saw in 1997 (around the same magnitude as 2019). Historical accounts from Asia show this event was disastrous, and the severe drought it caused led to crop failures, widespread famine and mortality, and incited war.

The wiggles that make up 500 years of reconstructed Indian Ocean Dipole variability. The red triangles show when extreme positive events occurred.
Author provided

As far as we can tell, this event shows just how extreme Indian Ocean Dipole variability can be, even without any additional prompting from external forces like human-caused climate change.

Why should we care?

Indian Ocean Dipole variability will continue to episodically bring extreme climate conditions to our region.

Drilling through fossilised coral layers to look into the past.
Nerilie Abram, Author provided

But previous studies, as well as ours, have shown human-caused climate change has shortened the gaps between these episodes, and this trend will continue. This is because climate change is causing the western side of the Indian Ocean to warm faster than in the east, making it easier for positive Indian Ocean Dipole events to establish.

In other words, drought-causing positive Indian Ocean Dipole events will become more frequent as our climate continues to warm.

In fact, climate model projections indicate extreme positive Indian Ocean Dipole events will occur three times more often this century than last, if high greenhouse gas emissions continue.




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This means events like last year will almost certainly unfold again soon, and we’re upping the odds of even worse events that, through the fossil coral data, we now know are possible.

Knowing we haven’t yet seen the worst of the Indian Ocean Dipole is important in planning for future climate risks. Future extremes from the Indian Ocean will act on top of long-term warming, giving a double-whammy effect to their impacts in Australia, like the record-breaking heat and drought of 2019.

But perhaps most importantly, rapidly cutting greenhouse gas emissions will limit how often positive Indian Ocean Dipole events occur in future.The Conversation

Nicky Wright, Research Fellow, Australian National University; Bethany Ellis, PhD Candidate, Australian National University, and Nerilie Abram, Professor; ARC Future Fellow; Chief Investigator for the ARC Centre of Excellence for Climate Extremes, Australian National University

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

Entire hillsides of trees turned brown this summer. Is it the start of ecosystem collapse?



Rachael Nolan, CC BY-NC

Rachael Helene Nolan, Western Sydney University; Belinda Medlyn, Western Sydney University; Brendan Choat, Western Sydney University, and Rhiannon Smith, University of New England

The drought in eastern Australia was a significant driver of this season’s unprecedented bushfires. But it also caused another, less well known environmental calamity this summer: entire hillsides of trees turned from green to brown.

We’ve observed extensive canopy dieback from southeast Queensland down to Canberra. Reports of more dead and dying trees from other regions across Australia are flowing in through the citizen science project, the Dead Tree Detective.




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A few dead trees are not an unusual sight during a drought. But in some places, it is the first time in living memory so much canopy has died off.

Ecologists are now pondering the implications. There are warnings that some Australian tree species could disappear from large parts of their ranges as the climate changes. Could we be witnessing the start of ecosystem collapse?

Extensive canopy dieback in Kains Flat, NSW, January 2020.
Matt Herbert

Why are canopies dying now?

Much of eastern Australia has been in drought since the start of 2017. While this drought is not yet as long as the Millennium Drought, it appears to be more intense. Many areas have received the lowest rainfall on record, including long periods of time with no rainfall. This has been coupled with above-average temperatures and extreme heatwaves.

The higher the temperature, the greater the moisture loss from leaves. This is usually good for a tree because it cools the canopy. But if there is not enough water in the soil, the increased water loss can push trees over a threshold, causing extensive leaf “scorching”, or browning. The extensive canopy dieback we have observed this summer suggests that the soil had finally become too dry for many trees.

Widespread rainfall deciciencies and higher temperatures across many parts of Australia.
Bureau of Meteorology

Are the trees dead?

Brown or bare trees are not necessarily dead. Many eucalypts can lose all their leaves but resprout after rain.

Many parts of eastern Australia are now flushed with green after rain. In these areas, it will be important to assess the extent of tree recovery. If trees are not showing signs of recovery after significant rainfall, they’re unlikely to survive. In some cases carbohydrate reserves – which trees need to resprout new leaves – may be too depleted for trees to recover.

Snowgums in the New England area resprouting in March 2020, following heavy rain. The trees lost most of their canopy during drought in 2019.
Trevor Stace, University of New England

The drought may also hinder post-fire recovery. Most eucalypt forests eventually recover from bushfires by resprouting new leaves. Some forests also recover when fire triggers seedlings to germinate.

But it’s likely that some forests now recovering from fire were already struggling with canopy dieback. So these two disturbances will test how resilient our forests are to back-to-back drought and bushfire.

Trees recovering from drought and/or fire may also enter the “dieback spiral”. The new flush of leaves following rain can make a particularly tasty meal for insects. Trees will then attempt to grow more foliage in response, but their ability to keep producing new leaves gradually declines as they deplete their carbohydrate reserves, and they can die.

Dieback spiral has led to extensive tree loss in the past, including in the New England area of NSW.

Should we be worried?

The capacity of eucalypts to resprout makes them naturally resilient to extended drought. There are some records of canopy dieback from severe droughts in the past, such as the Federation Drought. We assume (although we don’t know for sure) the forests recovered after these events. So they may bounce back after the current drought.

However, it’s hard not to be concerned. Climate change will bring increased drought, heatwaves and fires that could, over time, see extensive losses of trees across the landscape – as happened on the Monaro High Plain after the Millennium Drought.




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Australian research in 2016 warned that due to climate change, the habitat of 90% of eucalypt species could decline and 16 species were expected to lose their home environments within 60 years.

Such a change would have huge consequences for how ecosystems function – reducing the capacity for ecosystem services such as carbon storage, altering catchment water resources and reducing habitat for native animals.

Some trees resprouted new leaves after losing their canopy. But in some cases these leaves are now dying, like on these scribbly gums in the NSW Pilliga in August 2019.
Rachael Nolan

Where to from here?

Records of dead and dying trees on the Dead Tree Detective map.
Dead Tree Detective

Landholders can help bush on their property recover after drought, by protecting germinating seedlings from livestock and collecting local seed for later revegetation. Trees that appear dead should not be cut down as they may recover, and even if dead can provide valuable animal habitat.

Most importantly, however, we need to monitor trees carefully to see where they’ve died, and where they are recovering. A citizen science project, the Dead Tree Detective, is helping map the extent of tree die-off across Australia.

People send in photos of dead and dying trees – to date, over 267 records have been uploaded. These records can be used to target where to monitor forests during drought, including on-ground assessments of tree health and quantifying the physiological responses of trees to drought stress.

There is no ongoing forest health monitoring program in Australia, so this dataset is invaluable in helping us determine exactly how vulnerable Australia’s forests are to the double whammy of severe drought and bushfires.The Conversation

Rachael Helene Nolan, Postdoctoral research fellow, Western Sydney University; Belinda Medlyn, Professor, Western Sydney University; Brendan Choat, Associate Professor, Western Sydney University, and Rhiannon Smith, Research Fellow, University of New England

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

Why drought-busting rain depends on the tropical oceans


Andrew King, University of Melbourne; Andy Pitman, UNSW; Anna Ukkola, Australian National University; Ben Henley, University of Melbourne, and Josephine Brown, University of Melbourne

Recent helpful rains dampened fire grounds and gave many farmers a reason to cheer. But much of southeast Australia remains in severe drought.

Australia is no stranger to drought, but the current one stands out when looking at rainfall records over the past 120 years. This drought has been marked by three consecutive extremely dry winters in the Murray-Darling basin, which rank in the driest 10% of winters since 1900.

Despite recent rainfall the southeast of Australia remains in the grip of a multi-year drought.
Bureau of Meteorology

So what’s going on?

There has been much discussion on whether human-caused climate change is to blame. Our new study explores Australian droughts through a different lens.




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Rather than focusing on what’s causing the dry conditions, we investigated why it’s been such a long time since we had widespread drought-breaking rain. And it’s got a lot to do with how the temperature varies in the Pacific and Indian Ocean.

Our findings suggest that while climate change does contribute to drought, blame can predominately be pointed at the absence of the Pacific Ocean’s La Niña and the negative Indian Ocean Dipole – climate drivers responsible for bringing wetter weather.

Understanding the Indian Ocean Dipole.

What’s the Indian Ocean Dipole?

As you may already know, the Pacific Ocean influences eastern Australia’s climate through El Niño conditions (associated with drier weather) and La Niña conditions (associated with wetter weather).

The lesser known cousin of El Niño and La Niña across the Indian Ocean is called the Indian Ocean Dipole. This refers to the difference in ocean temperature between the eastern and western sides of the Indian Ocean. It modulates winter and springtime rainfall in southeastern Australia.




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When the Indian Ocean Dipole is “negative”, there are warmer ocean temperatures in the east Indian Ocean, and we see more rain over much of Australia. The opposite is true for “positive” Indian Ocean Dipole events, which bring less rain.

The Murray-Darling Basin experiences high rainfall variability, with decade-long droughts common since observations began. The graph shows seasonal rainfall anomalies from a 1961-1990 average with major droughts marked.
Author provided

What does it mean for the drought?

When the drought started to take hold in 2017 and 2018, we didn’t experience an El Niño or strongly positive Indian Ocean Dipole event. These are two dry-weather conditions we might expect to see at the start of a drought.

Rather, conditions in the Pacific and Indian Oceans were near neutral, with little to suggest a drought would develop.

So why are we in severe, prolonged drought?

The problem is we haven’t had either a La Niña or a negative Indian Ocean Dipole event since winter 2016. Our study shows the lack of these events helps explain why eastern Australia is in drought.

For the southeast of Australia in particular, La Niña or negative Indian Ocean Dipole events provide the atmosphere with suitable conditions for persistent and widespread rainfall to occur. So while neither La Niña or a negative Indian Ocean Dipole guarantee heavy rainfall, they do increase the chances.

What about climate change?

While climate drivers are predominately causing this drought, climate change also contributes, though more work is needed to understand what role it specifically plays.

Drought is more complicated and multidimensional than simply “not much rain for a long time”. It can be measured with a raft of metrics beyond rainfall patterns, including metrics that look at humidity levels and evaporation rates.

What we do know is that climate change can exacerbate some of these metrics, which, in turn, can affect drought.




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Climate change might also influence climate drivers, though right now it’s hard to tell how. A 2015 study suggests that under climate change, La Niña events will become more extreme. Another study from earlier this month suggests climate change is driving more positive Indian Ocean Dipole events, bringing even more drought.

Unfortunately, regional-scale projections from climate models aren’t perfect and we can’t be sure how the ocean patterns that increase the chances of drought-breaking rains will change under global warming. What is clear is there’s a risk they will change, and strongly affect our rainfall.

Putting the drought in context

Long periods when a La Niña or a negative Indian Ocean Dipole event were absent characterised Australia’s past droughts. This includes two periods of more than three years that brought us the Second World War drought and the Millennium drought.

The longer the time without a La Niña or negative Indian Ocean Dipole event, the more likely the Murray-Darling Basin is in drought.

In the above graph, the longer each line continues before stopping, the longer the time since a La Niña or negative Indian Ocean Dipole event occurred. The lower the lines travel, the less rainfall was received in the Murray Darling basin during this period. This lets us compare the current drought to previous droughts.

During the current drought (black line) we see how the rainfall deficit continues for several years, almost identically to how the Millennium drought played out.

But then the deficit increases strongly in late 2019, when we had a strongly positive Indian Ocean Dipole.

So when will this drought break?

This is a hard question to answer. While recent rains have been helpful, we’ve developed a long-term rainfall deficit in the Murray-Darling Basin and elsewhere that will be hard to recover from without either a La Niña or negative Indian Ocean Dipole event.




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The most recent seasonal forecasts don’t predict either a negative Indian Ocean Dipole or La Niña event forming in the next three months. However, accurate forecasts are difficult at this time of year as we approach the “autumn predictability barrier”.

This means, for the coming months, the drought probably won’t break. After that, it’s anyone’s guess. We can only hope conditions improve.The Conversation

Andrew King, ARC DECRA fellow, University of Melbourne; Andy Pitman, Director of the ARC Centre of Excellence for Climate System Science, UNSW; Anna Ukkola, Research Fellow, Australian National University; Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne, and Josephine Brown, Lecturer, University of Melbourne

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

‘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.

Heavy rains are great news for Sydney’s dams, but they come with a big caveat


Ian Wright, Western Sydney University and Jason Reynolds, Western Sydney University

Throughout summer, Sydney’s water storage level fell alarmingly. Level 2 water restrictions were imposed and the New South Wales government prepared to double the capacity of its desalination plant.

But then it began to rain, and rain. Sydney water storages jumped from 41% in early February to 75% now – the highest of any capital city in Australia.

This is great news for the city, but it comes with a big caveat. Floodwaters will undoubtedly wash bushfire debris into reservoirs – possibly overwhelming water treatment systems. We must prepare now for that worst-case pollution scenario.

Reservoirs filled with rain

The water level of Sydney’s massive Lake Burragorang – the reservoir behind Warragamba Dam – rose by more than 11 meters this week. Warragamba supplies more than 80% of Sydney’s water.

Other Sydney water storages, including Nepean and Tallowa dams, are now at 100%.
WaterNSW report that 865,078 megalitres of extra water has been captured this week across all Greater Sydney’s dams.

This dwarfs the volume of water produced by Sydney’s desalination plant, which produces 250 megalitres a day when operating at full capacity. Even at this rate, it would take more than 3,400 days (or nine years) to match the volume of water to added to Sydney’s supply this week.

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The Warragamba Dam before the drought and after the recent heavy rains.

But then comes the pollution

Thankfully, the rain appears to have extinguished bushfires burning in the Warragamba catchment for months.

But the water will also pick up bushfire debris and wash it into dams.

Over the summer, bushfires burnt about 30% of Warragamba Dam’s massive 905,000 hectare water catchment, reducing protective ground cover vegetation. This increases the risk of soil erosion. Rain will wash ash and sediment loads into waterways – adding more nitrogen, phosphorous and organic carbon into water storages.




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Waterways and ecosystems require nutrients like phosphorous and nitrogen, but excess nutrients aren’t a good thing. They bring contamination risks, such as the rapid growth of toxic blue-green algae.

Drinking water catchments will always have some degree of contamination and water treatment consistently provides high quality drinking water. But poor water quality after catchment floods is not without precedent.

We’ve seen this before

In August 1998, extreme wet weather and flooding rivers filled the drought-affected Warragamba Dam in just a few days.

This triggered the Cryptosporidium crisis, when the protozoan parasite and the pathogen Giardia were detected in Sydney’s water supplies. It triggered health warnings, and Sydneysiders were instructed to boil water before drinking it. This event did not involve a bushfire.




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The Canberra bushfires in January 2003 triggered multiple water quality problems. Most of the region’s Cotter River catchments, which hold three dams, were burned. Intense thunderstorms in the months after the bushfire washed enormous loads of ash, soil and debris into catchment rivers and water reservoirs.

This led to turbidity (murkiness), as well as iron, manganese, nitrogen, phosphorus and carbon in reservoir waters. The inflow of organic material also depleted dissolved oxygen which triggered the release of metals from reservoir sediment. At times, water quality was so poor it couldn’t be treated and supplied to consumers.

The ACT Government was forced to impose water restrictions, and built a A$38 million water treatment plant.

Have we come far enough?

Technology in water treatment plants has developed over the past 20 years, and water supply systems operates according to Australian drinking water guidelines.

Unlike the 1998 Sydney water crisis, WaterNSW, Sydney Water and NSW Health now have advanced tests and procedures to detect and manage water quality problems.

In December last year, WaterNSW said it was aware of the risk bushfires posed to water supplies, and it had a number of measures at its disposal, including using booms and curtains to isolate affected flows.

However at the time, bushfire ash had already reportedly entered the Warragamba system.

The authors crossing the Coxs River during very low flow last September.
Author provided

Look to recycled water

Sydney’s water storages may have filled, but residents should not stop saving water. We recommend Level 2 water restrictions, which ban the use of garden hoses, be relaxed to Level 1 restrictions which ban most sprinklers and watering systems, and the hosing of hard surfaces.

While this measure is in place, longer term solutions can be explored. Expanding desalination is a popular but expensive option, however greater use of recycled wastewater is also needed.




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Highly treated recycled water including urban stormwater and even treated sewage should be purified and incorporated into the water supply. Singapore is a world leader and has proven the measure can gain community acceptance.

It’s too early to tell what impact the combination of bushfires and floods will have on water storages. But as extreme weather events increase in frequency and severity, all options should be on the table to shore up drinking water supplies.The Conversation

Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University and Jason Reynolds, Senior Lecturer in Geochemistry, Western Sydney University

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