A current affair: the movement of ocean waters around Australia



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Where do the ocean waters that wash the Gold Coast come from?
Flickr/LJ Mears , CC BY-NC-SA

Charitha Pattiaratchi, University of Western Australia; Ems Wijeratne, University of Western Australia, and Roger Proctor, University of Tasmania

Many people in Australia will head to the beach this summer and that’ll most likely include a dip or a plunge into the sea. But have you ever wondered where those ocean waters come from, and what influence they may have?

Australia is surrounded by ocean currents that have a strong controlling influence on things such as climate, ecosystems, fish migrations, the transport of ocean debris and on water quality.

We did a study, published in April 2018, that helps to give us a better understanding of those ocean currents.

Surface currents around the Australian continent.
Ems Wijeratne/Charitha Pattiaratchi/Roger Proctor



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Go with the flow: Indian Ocean

Our 15 year simulation indicates that water from the Pacific Ocean enters the Indonesian Archipelago through the Mindanao current (north) and Halmahera Sea (south).

It then enters the Indian ocean as the Indonesian Throughflow between many Indonesian Islands, with flow through the Timor Passage being the most dominant.

Most of this water flows west as the South Equatorial Current. Re-circulation of the SEC creates the Eastern Gyre that contributes to the Holloway Current. This in turn feeds the Leeuwin Current – the longest boundary current in the world (Ocean currents that flow adjacent to a coastline are called boundary currents)

The Leeuwin Current is the major boundary current along the west coast and as it moves southward. Indian Ocean water is supplied by the South Indian Counter Current increasing the Leeuwin Current transport by 60%.

The Leeuwin Current turns east at Cape Leeuwin, in Western Australia’s south-west, and continues to Tasmania as the South Australian and Zeehan Currents.

The Leeuwin Current passes the lighthouse at the Cape Leeuwin in WA.
Flickr/Cheng, CC BY-NC-ND

There is a strong seasonal variation in the strength of the boundary currents in the Indian Ocean with a progression southwards of the peak transport along the coast.

The Holloway Current peaks in April/May (coinciding with changes in the monsoon winds), the Leeuwin Current reaches a maximum along the west and south coasts in June and August.




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Go with the flow: Pacific Ocean

In the Pacific Ocean, the northern branches of the South Equatorial Current are the main inputs initiating the Hiri Current and East Australian Current.

At around latitude 15 degrees south the currents split in two: southward to form the East Australian Current, and northward to form the Hiri Current which contributes to a clockwise gyre in the Gulf of Papua.

The East Australian Current is the dominant current in the region transporting 33 million cubic metres of water per second southward.

At around 32S, the East Australian Current separates from the coast and 60% of the water flows eastward to New Zealand as the Tasman Front. The remaining 40% flows southward as the East Australian Current extension and contributes to the Tasman Outflow.

The Tasman outflow is the major conduit of water from the Pacific to Indian Ocean and contributes to the Flinders Current, flowing westward from Tasmania and past Cape Leeuwin into the Indian Ocean.

Along the southern continental slope, the Flinders Current appears as an undercurrent beneath the Leeuwin Current and a surface current further offshore. The Flinders Current contributes to the Leeuwin Undercurrent directly as a northward flow, flowing to the north-west of Australia in water depths 300 metres to 800 metres.

Impact of the currents

Understanding ocean circulation is a fundamental tenet of physical oceanography and scientists have been charting the pathways of ocean currents since the American hydrographer Matthew Maury, one of the founders of oceanography, who first charted the Gulf Stream in 1855.

One of the first maps of circulation around Australia was by Halliday (1921) who showed the movement of “warm” and “cold” waters around Australia. Although some of the major features (such as the East Australian Current) were correctly identified, a more fine scale description is now available.

Ocean surface currents around Australia by Halliday 1921.

The unique feature of ocean currents around Australia is that along both east and west coasts they transport warmer water southwards and influence the local climate, particularly air temperature and rainfall, as well as species distribution.




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For example, the south west of Australia is up to 5C warmer in winter and receives more than double the rainfall compared to regions located on similar latitudes along western coastlines of other continents.

Similarly many tropical species of fish are found in the southwest of Australia that hitch a ride on the ocean currents.

The Pacific Ocean is the origin of waters around Australia with a direct link to the east and an indirect link to west.

Ocean water from the Pacific Ocean flows through the Indonesian Archipelago, a region subject to high solar heating and rainfall runoff, creating lower density water. This water, augmented by water from the Indian Ocean, flows around the western and southern coasts, converging along the southern coast of Tasmania.

So next time you head for a dip in the coastal waters around Australian, spare a thought for where that water has come from and where it may be going next.The Conversation

Time for a plunge in the water at Bondi Beach, NSW.
Flickr/Roderick Eime, CC BY-ND

Charitha Pattiaratchi, Professor of Coastal Oceanography, University of Western Australia; Ems Wijeratne, Assistant Professor, UWA Oceans Institute, University of Western Australia, and Roger Proctor, Director, Australian Ocean Data Network, University of Tasmania

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

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We’re in the era of overtourism but there is a more sustainable way forward



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Many European holiday destinations now struggle with overcrowding and pollution.
from http://www.shutterstock.com, CC BY-ND

Regina Scheyvens, Massey University

If you live in a tourist destination, you might dread the holiday invasion. Likewise, disgruntled tourists complain about crowded and polluted beaches, national parks or attractions.

Graffiti in Oviedo, northern Spain, following a spate of attacks on tourism facilities in Barcelona.
EPA/ALBERTO MORANTE, CC BY-ND

Overtourism is now a serious issue in many parts of the world. A good visitor experience may not be a finite resource in the same way as oil, but many popular destinations in Europe are reaching what could be termed “peak tourism”.

Concerns have been raised from Amsterdam to Dubrovnik about noise pollution, crowded parks, pressure on public facilities and rising rents. And in what is depicted as a “global battle” between travellers and locals, anti-tourism street marches have occurred in Barcelona and Venice.




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Unsustainable tourism growth

Tucked away in a seemingly idyllic spot in the South Pacific, New Zealand is not immune to such concerns, which is why Massey University is hosting the world’s first research conference on tourism and the sustainable development goals this month.

Between 2013 and 2018, international tourist arrivals in New Zealand grew by 1.2 million to a total of 3.8 million. During the 12 months to March last year, tourists spent almost $40 billion, and the industry now provides one in every 12 jobs.

Economists see this growth as very positive for the country’s development, but many New Zealanders are ambivalent: 39% have expressed concern over the negative impacts of the growth in international visitors. The pressure on some destinations is particularly intense. For example, the 20,000 permanent residents of the summer and winter playground of Queenstown play host to around three million visitors a year.

Tourists digging holes in the vulcanic sand of a hot water beach in New Zealand.
from http://www.shutterstock.com, CC BY-ND



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Meanwhile local government bodies lament the pressure on public infrastructure and demands for waste disposal from freedom campers. Contractors at four Central Otago freedom camping sites have struggled to clear 16 tonnes of rubbish accumulated over the last two months.

A test case for concerns about the promise versus the pitfalls of tourism is the case of cruise tourism in Akaroa Harbour. The battle line lies between some business owners whose livelihoods depend on cruise tourists and local residents who feel their beautiful harbour and quaint town are marred by air and noise pollution and congestion associated with hundreds of tourists dropping in on their town with each cruise.




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Why Australia might be at risk of ‘overtourism’


In Australia, the Guinness World Record-certified whitest sand beach in the world – Hyams Beach – has turned away thousands of potential visitors during the Christmas and New Year period. There are only 110 permanent residents and 400 parking spaces, but up to 5000 tourists wanting to visit the beach each day during summer.

These experiences reflect the pressures and tensions tourism brings to many parts of the world, and the need for better ways of regulating tourist activity and capturing the gains from tourism.

A more sustainable way forward

It is clear that most people do not wish to see an end to tourism. But they do want the industry to be far more sustainable. While the term “sustainable tourism” has long been criticised for its lack of clout – and the way it can be seen as merely “sustaining tourism”, there is a way forward. We can look to the United Nations’ 17 sustainable development goals (SDGs), ratified in 2015 by 193 countries and set to guide global development through to 2030.

The SDGs require governments, civil society and business interests to play their parts in creating a more sustainable world. Furthermore, they are multi-faceted, considering social, economic and environmental aspects of sustainability.




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The SDGs can help to guide the tourism industry to make more sustainable choices. For example, a strategy by hotels, cruise ships and restaurants to buy as much fresh produce from local farmers as possible would shorten the supply chain and save food miles (thus contributing to SDG 13 on combating climate change). It would also enhance local development (SDG 1 on eliminating poverty).

Tourist resorts in the Pacific could tackle the sexual harrassment from guests that many resort employees experience to show they care about SDG 8 on “decent work for all” and SDG 5 on “empowering all women and girls”.

Tourism trades in luxury products and indulgent experiences, and as such it places a heavy burden on the natural environment and results in waste management issues. SDG 12 on sustainable production and consumption can encourage companies to offer tourists more sustainable products and to reduce wastage of energy, fresh water and food.

Efforts to capture the benefits of tourism while preventing overtourism should pay careful attention to the SDGs.The Conversation

Regina Scheyvens, Professor of Development Studies, Massey University

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

Recycling is not enough. Zero-packaging stores show we can kick our plastic addiction



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Frenco, a zero-waste store in Montreal.
Benoit Daoust/Shutterstock.com

Sabrina Chakori, The University of Queensland and Ammar Abdul Aziz, The University of Queensland

Wrapped, sealed, boxed, cling-filmed and vacuum packed. We have become used to consumables being packaged in every way imaginable.

The history of “packaging” goes back to the first human settlements. First leaves, gourds and animals skins were used. Then ceramics, glass and tin. Then paper and cardboard. But with the invention of plastic and the celebration of “throwaway living” since the 1950s, the environmental costs of an overpackaged world have become manifest.

Plastic now litters the planet, contaminating ecosystems and posing a significant threat to wildlife and human health. Food and beverage packaging accounts for almost two-thirds of total packaging waste. Recycling, though important, has proven an incapable primary strategy to cope with the scale of plastic rubbish. In Australia, for example, just 11.8% of the 3.5 million tonnes of plastics consumed in 2016-2017 were recycled.

Bananas wrapped in single-use plastic packaging.
Sabrina Chakori

Initiatives to cut down on waste can initially be strongly resisted by consumers used to the convenience, as shown by the reaction to Australia’s two major supermarket chains phasing out free single-use plastic shopping bags. But after just three months, shoppers have adapted, and an estimated 1.5 billion bags have been prevented from entering the environment.

Can we dispose with our disposable mentality further, by doing something to cut down on all the packaging of our food and beverages?

Yes we can.

The emergence of zero-packaging food stores is challenging the idea that individually packaged items are a necessary feature of the modern food industry. These new businesses demonstrate how products can be offered without packaging. In doing so they provide both environmental and economic benefits.

The zero-packaging alternative

Zero-packaging shops, sometimes known as zero-waste grocery stores, allow customers to bring and refill their own containers. They offer food products (cereals, pasta, oils) and even household products (soap, dishwashing powder). You simply bring your own jars and containers and buy as little or as much as you need.

Negozio Leggero is a zero-packaging chain with stores in Italy, France and Switzerland.
Negozio Leggero

These stores can already be found in many countries across the world. They are more than just individual trading businesses making a small difference.

They are part of an important and growing trend promoting an environmentally sustainable “reuse” mentality. Their way of doing business shows we can change the current ‘linear’ economic system in which we continuously take, make, use and throw away materials.

Rethinking the system

Food packaging is part and parcel of a globalised food market. The greater the distance that food travels, the more packaging is needed.

Zero-packaging stores encourage sourcing locally. They can therefore play an important role in enhancing local economy and supporting local producers. They can help break globalised agribusiness monopolies, regenerating the diversity of rural enterprises and communities. The book Home Grown: The Case for Local Food in a Global Market illustrates the benefits of reclaiming back the food industry.




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Packaging also contributes to another problem with the current industrialised food system. It doubles as an advertising tool, using all the psychological tricks that marketers have to persuade us to buy a brand. These strategies appeal to desire, encouraging people to buy more than what they really need. This has arguably exacerbated problems such as obesity and food waste. It has given multinational conglomerates with large marketing budgets an advantage over small and local producers.

Next steps

Not all of packaging is wasteful. It can stop food spoiling, for example, and enables us to enjoy foods not locally produced. But what is driving the growth of the global food packaging market – expected to be worth US$411.3 billion by 2025 – is rising demand for single-serve and portable food packs due to “lifestyle changes”. Most of us recognise these are not lifestyle changes for the better; they are the result of us spending more time working or commuting, and eating more processed and unhealthier food.




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Zero-packaging stores show, in their own small way, a viable and healthier alternative to the current system. Both for ourselves, local economies and the planet.

While these shops are still niche, governments interested in human and environmental health can help them grow. Bans on plastic bags point to what is possible.

How easily we have adapted to no longer having those bags to carry food a few metres to the car and then to the kitchen show that we, as consumers, can change our behaviour. We can choose, when possible, unpacked products. There is, of course, a small sacrifice in the form of convenience, but we just might find that we benefit more, both personally and for a greater environmental, economic and social good.The Conversation

Sabrina Chakori, PhD Candidate, The University of Queensland and Ammar Abdul Aziz, Lecturer, The University of Queensland

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

Bison are back, and that benefits many other species on the Great Plains



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A young bull bison grazes on the Tallgrass Prairie Preserve, Pawhuska, Oklahoma.
Matthew Moran, CC BY-ND

Matthew D. Moran, Hendrix College

Driving north of Pawhuska, Oklahoma, an extraordinary landscape comes into view. Trees disappear and an immense landscape of grass emerges, undulating in the wind like a great, green ocean.

This is the Flint Hills. For over a century it has been cattle country, a place where cows grow fat on nutritious grasses. More recently, a piece of this landscape was transformed in 1992 when the nonprofit Nature Conservancy bought the Barnard Ranch. It created a nature reserve there, the Tallgrass Prairie Preserve, which now covers almost 40,000 acres.

A central element of the group’s conservation strategy was reintroducing the American bison (Bison bison), which had been eradicated from the land in the mid-1800s. Releasing the first bison in 1993 was a step toward restoring part of an ecosystem that once stretched from Texas to Minnesota.

Today some 500,000 bison have been restored in over 6,000 locations, including public lands, private ranches and Native American lands. As they return, researchers like me are gaining insights into their substantial ecological and conservation value.

Near extinction

It was not always certain that bison could rebound. Once numbering in the tens of millions, they dominated the Great Plains landscape until the late 1800s, anchoring a remarkable ecosystem that contained perhaps the greatest concentration of mammals on Earth. That abundance was wiped out as settlers and the U.S. government engaged in a brutally effective campaign to eradicate the ecosystem and the native cultures that relied on it.

Bison were shot by the millions, sometimes for “sport,” sometimes for profit, and ultimately to deprive Native Americans of vital resources. By 1890 fewer than 1,000 bison were left, and the outlook for them was bleak. Two small wild populations remained, in Yellowstone National Park and northern Alberta, Canada; and a few individuals survived in zoos and on private ranches.

Bison skulls collected during the slaughter, mid-1870s.
Source unknown

Recovery

Remarkably, a movement developed to save the bison and ultimately became a conservation success story. Some former bison hunters, including prominent figures like William “Buffalo Bill” Cody and future President Theodore Roosevelt, gathered the few surviving animals, promoted captive breeding and eventually reintroduced them to the natural landscape.

With the establishment of additional populations on public and private lands across the Great Plains, the species was saved from immediate extinction. By 1920 it numbered about 12,000.

Bison remained out of sight and out of mind for most Americans over the next half-century, but in the 1960s diverse groups began to consider the species’ place on the landscape. Native Americans wanted bison back on their ancestral lands. Conservationists wanted to restore parts of the Plains ecosystems. And ranchers started to view bison as an alternative to cattle production.

More ranches began raising bison, and Native American tribes started their own herds. Federal, state, tribal and private organizations established new conservation areas focusing in part on bison restoration, a process that continues today in locations such as the Tallgrass Prairie National Preserve in Kansas and the Fort Peck Reservation in Montana.

By the early 2000s, the total North American population had expanded to 500,000, with about 90 percent being raised as livestock – but often in relatively natural conditions – and the rest in public parks and preserves. For scientists, this process has been an opportunity to learn how bison interact with their habitat.

Male bison grazing and bellowing in Yellowstone National Park.
NPS/Shan Burson711 KB (download)

Improving prairie landscapes

Bison feed almost exclusively on grasses, which, because they grow rapidly, tend to out-compete other plants. Bison’s selective grazing behavior produces higher biodiversity because it helps plants that normally are dominated by grasses to coexist.

Because they tend to graze intensively on recently burned zones and leave other areas relatively untouched, bison create a diverse mosaic of habitats. They also like to move, spreading their impacts over large areas. The variety they produce is key to the survival of imperiled species such as the greater prairie chicken (Tympanuchus cupido) that prefer to use different patches for different behaviors, such as mating and nesting.

Bison impacts don’t stop there. They often kill woody vegetation by rubbing their bodies and horns on it. And by digesting vegetation and excreting their waste across large areas, they spread nutrients over the landscape. This can produce higher-quality vegetation that benefits other animals.

Grazing by bison on this stretch of prairie has produced an increase in forbs (nongrass flowering plants).
Matthew Moran, CC BY-ND

Studies, including my own research, have shown that bison-induced changes in vegetation composition and quality grazing can increase the abundance and diversity of birds and insects in tallgrass prairies. Bison also affect their environment by wallowing – rolling on the ground repeatedly to avoid biting insects and shed loose fur. This creates long-lasting depressions that further enhance plant and insect diversity, because they are good habitats for plant and animal species that are not found in open areas of the prairie. In contrast, cattle do not wallow, so they do not provide these benefits.

It is hard to determine the ecological role that bison played before North America was settled by Europeans, but available evidence suggests they may have been the most impactful animal on the Plains – potentially a keystone species whose presence played a unique and crucial role in the ecology of prairies.

Male prairie chickens in the Flint Hills, Oklahoma, displaying for mates.
Greg Kramos/Wikimedia, CC BY

The growth of bison ranching

The return of the bison has generated a new industry on the Plains. The National Bison Association promotes these animals as long-lived, hardy and high-quality livestock. The group hopes to double bison numbers through its Bison 1 Million commitment, a program designed to increase interest in bison ranching and consumption.

Advocates cite health, ecological and ethical arguments in support of bison ranching. Bison meat is lean and has a high protein content. Many bison ranchers are committed to ethical and sustainable ranching practices, which sometimes are lacking in modern industrial livestock farming.

“I have a love of nature and want to protect it. It was one of my family’s goals to restore the grasslands. Bison helped us regenerate the land,” Mimi Hillenbrand, owner and operator of the 777 Bison Ranch near Rapid City, South Dakota told me. She adds, “I love the animal. We are lucky that we brought them back. I learn every day from them.”

777 Bison Ranch owner Mimi Hillenbrand explains how raising bison has helped her family restore the health of their South Dakota land.

Thinking bigger

Will bison live on in relatively small, isolated herds as they do now, or something greater? The American Prairie Reserve, a Montana-based nonprofit, has a big and controversial idea: creating an ecologically functioning 3 million acre preserve of private, public and tribal lands in northeast Montana, with a herd of over 10,000 bison – the largest single population in the world. Although this would be small compared to the millions that once existed, it still would be something to see.

Bison were saved through the combined efforts of conservationists, scientists, ranchers and ultimately the general public. As their comeback continues, I believe that they can teach us how to be better stewards of the land and provide a future for the Plains where ecosystems and human cultures thrive.The Conversation

Matthew D. Moran, Professor of Biology, Hendrix College

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

The Darling River is simply not supposed to dry out, even in drought



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Puddles in the bed of the Darling River are a sign of an ecosystem in crisis.
Jeremy Buckingham/Flickr, CC BY-SA

Fran Sheldon, Griffith University

The deaths of a million of fish in the lower Darling River system over the past few weeks should come as no surprise. Quite apart from specific warnings given to the NSW government by their own specialists in 2013, scientists have been warning of devastation since the 1990s.

Put simply, ecological evidence shows the Barwon-Darling River is not meant to dry out to disconnected pools – even during drought conditions. Water diversions have disrupted the natural balance of wetlands that support massive ecosystems.

Unless we allow flows to resume, we’re in danger of seeing one of the worst environmental catastrophes in Australia.




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Dryland river

The Barwon-Darling River is a “dryland river”, which means it is naturally prone to periods of extensive low flow punctuated by periods of flooding.

However, the presence of certain iconic river animals within its channels tell us that a dry river bed is not normal for this system. The murray cod, dead versions of which have recently bought graziers to tears and politicians to retch, are the sentinels of permanent deep waterholes and river channels – you just don’t find them in rivers that dry out regularly.

Less conspicuous is the large river mussel, Alathyria jacksoni, an inhabitant of this system for thousands of years. Its shells are abundant in aboriginal middens along the banks. These invertebrates are unable to tolerate low flows and low oxygen, and while dead fish will float (for a while), shoals of river mussels are probably dead on the river bed.

This extensive drying event will cause regional extinction of a whole raft of riverine species and impact others, such as the rakali. We are witnessing an ecosystem in collapse.

Catastrophic drying

We can see the effects of permanent drying around the world. The most famous example is the drying of the Aral Sea in Central Asia. Once the world’s fourth largest inland lake, it was reduced to less than 10% of its original volume after years of water extraction for irrigation.

The visual results of this exploitation still shock: images of large fishing boats stranded in a sea of sand, abandoned fishing villages, and a vastly changed microclimate for the regions surrounding the now-dry seabed. Its draining has been described as “the world’s worst environmental disaster”.




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So, what does the Aral Sea and its major tributaries and the Darling River system with its tributary rivers have in common? Quite a lot, actually. They both have limited access to the outside world: the Aral Sea basin has no outflow to the sea, and while the Darling River system connects to the River Murray at times of high flow, most of its water is held within a vast network of wetlands and floodplain channels. Both are semi-arid. More worryingly, both have more the 50% of their average inflows extracted for irrigation.

There is one striking difference between them. The Aral Sea was a permanent inland lake and its disappearance was visually obvious. The wetlands and floodplains of the Barwon-Darling are mostly ephemeral, and the extent of their drying is therefore hard to visualise.




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An orphaned ship in former Aral Sea, near Aral, Kazakhstan.
Wikipedia

All the main tributaries of the Darling River have floodplain wetland complexes in their lower reaches (such as the Gwydir Wetlands, Macquarie Marshes and Narran Lakes). When the rivers flow they absorb the water from upstream, filling before releasing water downstream to the next wetland complex; the wetlands acting like a series of tipping buckets. Regular river flows are essential for these sponge-like wetlands.

So, how has this hydrological harmony of regular flows and fill-and-spill wetlands changed? And how does this relate to the massive fish kills we are seeing in the lower Darling system?




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How is oxygen ‘sucked out’ of our waterways?


While high flows will still make it through the Barwon-Darling, filling the floodplains and wetlands, and connecting to the River Murray, the low and medium flow events have disappeared. Instead, these are captured in the upper sections of the basin in artificial water storages and used in irrigation.

This has essentially dried the wetlands and floodplains at the ends of the tributaries. Any water not diverted for irrigation is now absorbed by the continually parched upstream wetlands, leaving the lower reaches vulnerable when drought hits.

By continually keeping the Barwon-Darling in a state of low (or no) flow, with its natural wetlands dry, we have reduced its ability to cope with extended drought.




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Why a wetland might not be wet


While droughts are a natural part of this system and its river animals have adapted, they can’t adjust to continual high water caused in some areas by water diversions – and they certainly can’t survive long-term drying.

The Basin Plan has come some way in restoring some flows to the Barwon-Darling, but unless we find a way to restore more of the low and medium flows to this system we are likely witnessing Australia’s worst environmental disaster.




Read more:
It will take decades, but the Murray Darling Basin Plan is delivering environmental improvements


The Conversation


Fran Sheldon, Professor, Australian Rivers Institute, Griffith University, Griffith University

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