Life on the floodplains

By Karen McGhee 11 May 2011
Reading Time: 10 Minutes Print this page
Sporadic heavy rains bring a slow tide of change to parched lands in the Murray-Darling basin.

This article was first published in the Australian Geographic journal in 2008.

AS LIGHTNING CRACKED and thunder rumbled across the skies over central Queensland late 2007, rain began falling as it hadn’t done for almost a decade, signalling a respite from one of the worst droughts on record for much of eastern Australia.

Almost 1000km to the south-west in the red dirt and mulga country of semi-arid NSW, local showers had also been dampening the dust on Naree, a 14,000ha pastoral property owned by the Kaluders – Paul, Debbie, and their kids Damon, Jared and Tegan. But the family was more interested in the Queensland falls and listened eagerly to the radio for flood warnings, traded news by phone with distant neighbours about river gauge readings on the Warrego River and its tributaries…and waited.

After managing other people’s properties in WA and Queensland for much of their married life, Paul and Debbie bought Naree in late 2006, optimistic they’d finally secured their own piece of outback paradise. The property lies 130 km north-west of Bourke, just east of the sometimes spectacular ephemeral wetlands of the Cuttaburra Basin, in flood country, where land attracts a premium because local creeks and rivers can be expected, every so often, to burst their banks and spill rejuvenating silt-laden water across the landscape.

The Kaluders’ purchase, however, had been speculative, made at the drought’s peak, with large parts of Naree suffering from overgrazing. No-one in the district knew how much of the property might truly flood. Paul, however, had learned to read the latent signs of productivity in this type of environment. Naree’s many hectares of grey-black soil were a certain sign of past inundations. And there were also clues in the vegetation: large stands of telltale eucalypt species – coolibah, yapunyah and river red gum – as well as paddocks of lignum, all dead, dying or severely stressed but all dependent on occasional flooding for long-term survival.

For more than four weeks, Paul tracked the passage of the Queensland water: down the streams of the Carnarvon Range and into the Warrego, past the townships of Augathella and Charleville, and over the weir at Cunnamulla. Some continued down the Warrego and finally, south of Bourke, trickled into the mighty Darling River – one of Australia’s longest. And some coursed down Cuttaburra Creek, just south of Cunnamulla, and eventually onto Naree.

“We saw it coming down this channel here, across the power line, and met it with the car,” says Paul, pointing to a map of his sprawling property. “It came in at walking pace, creeping across and spreading out.”

Sporadic Queensland rains continued feeding the Cuttaburra system and by March, more than one-third of Naree was underwater. The Kaluders knew they’d found their inland Eden. “We don’t see this as our water. It comes, does its thing and keeps on going,” says Debbie. “Now we wait for it to evaporate, and as the grass seeds germinate behind it, the feed will come on and we’ll be able to increase our stock.”

Of droughts and flooding rains

Naree’s flooded hectares are among millions within the 1 millionsq. km Murray-Darling Basin that have been inundated by water. Much of the area is enjoying water for the first time this century. Many creeks and rivers have flowed after years of dryness and huge inland lakes, both salt- and freshwater, have formed over once-parched claypans and cracked earth. Swamps, billabongs and wetlands have filled, and floodplains have been soaked and nourished.

For a few short months, large parts of the outback have been transformed from a dry, seemingly lifeless expanse of rocks and dust, sparsely vegetated by stunted plants, to huge oases rippling with life. Sturt, Burke and other 19th-century European explorers who searched for Australia’s mythical inland sea, would have felt vindicated had they found this.

The water can last just weeks or months in the shallowest of the lakes and across the floodplains. But in some billabongs, creeks and rivers, it can sit for years, eventually fading into a series of slowly evaporating, isolated pools boosted occasionally by small flows and local rain. Although remoteness and infrequent flows make these rivers difficult to study, a handful of researchers has been gathering data on them for up to 20 years. As debate over river water rights and allocations has grown during the past decade, research activity has increased substantially. What scientists have been finding repeatedly confirms the distinctive and fragile nature of these systems.

Australia’s inland rivers share some similarities with the ephemeral wetland environments of southern Africa. But these rarely flowing systems are for the most part unlike those anywhere else in the world. For example, they frequently peter out into little more than a trickle, whereas most of the world’s rivers grow in size as floods advance downstream. The continent’s low-lying and highly eroded topography also means they tend to wander wildly across the landscape and, during the bigger flows, sprout meandering branches that spread their influence well beyond the river bank.

“Our work has been repeatedly showing that Australian rivers don’t behave the way the rivers described in scientific textbooks traditionally do,” says Professor Martin Thoms, head of the University of Canberra’s Riverine Landscapes Research Laboratory. He describes a river’s flow regime as its heartbeat. “US and European rivers, for example, have quite a regular heartbeat, but Australian rivers have irregular and unpredictable ones. It means it’s impossible to reliably predict when and to what extent these inland rivers might flow. We’ve got to understand and embrace this extraordinary natural variability, particularly from a management perspective.”

It’s wondrous enough seeing water, kilometres of it in all directions, near the middle of Australia. But the spectacular explosion of life these rivers trigger when they flow is truly awe-inspiring. Biological limits out here are set by the length of the Dry, and the erratic rising and falling of rivers has unquestionably influenced inland Australia’s ecological rhythms for millennia. When the rivers are down, life is often forced to eke out a cryptic, waterless existence. But when the big flows come, plants and animals respond at a rapid pace and on a massive scale.

Birds suddenly appear en masse: hundreds of thousands of waterbirds – some species stopping briefly en route to distant shores, some out west for a feed and many others that aggregate in huge breeding colonies of 10,000 or more pairs. No-one is quite sure how the birds know when and where Australia’s inland river systems are flowing. One theory is they can sense the low-pressure systems associated with rainfall events that bring floods. Another is they visually navigate by the water flows as if they were riverine highways.

The first to arrive are waders, such as stilts and avocets, which forage at the flood’s front on spiders, insects and other invertebrates flushed out of subterranean burrows as water sinks and replenishes the watertable.

At the same time, hardy zooplankton eggs – some capable of regeneration after more than a quarter of a century – float out of the soil, quickly turning the water into a soup of booming populations of microscopic freshwater crustaceans and molluscs. Research by Dr Kim Jenkins, an invertebrate ecologist at the University of NSW, has found up to 20,000 of these tiny creatures per litre in the floodwaters of some western NSW rivers. That’s high by world standards and it underpins an extraordinary level of productivity and a complex mesh of food webs. Native fish, such as yellowbelly, exploit the invertebrate bounty and spawn when these rivers rise, as do larger crustaceans, such as yabbies. And although they remain poorly studied, the amphibians that survive in this extreme environment are believed to also make enormous ecological contributions to the productivity of these systems.

As fish levels rise, diving birds – cormorants, pelicans and others – arrive to exploit the new food source, and egrets and herons forage on the floodplain for insects and frogs. Raptors follow and, around breeding colonies, it’s common to see large numbers of them patrolling the skies, watching for weak or abandoned chicks. Other land birds, including arid-zone honeyeater species, also experience population booms at these times. And the largest flocks of budgerigars are always seen after floods.

Not all the lakes and wetlands provide suitable nesting habitat for wetland birds, but several support huge breeding colonies of such ecological importantance that they are cited in international waterbird agreements. One of the most important is believed to be Narran Lake, an ephemeral wetland system about 45 km north-east of Brewarrina, NSW.

Water buy-backs for the floodplains

The Narran system is fed by the Narran River which, in full flow, inundates two large lakes and extensive flood-plains. But the drought and rising irrigation demands have severely restricted the river’s reach in recent years.

In 2003, University of NSW wetlands ecology student Kate Brandis nominated Narran as the study site for her PhD. She planned to document the spectacular bird-breeding events that, according to both recent whitefella and longer-term indigenous records, historically occurred there every couple of years. By last year, the Narran system had been mostly dry for much of a decade and Kate believed she’d never witness the sort of breeding event she’d hoped to study.

But last December she watched the progress of the low-pressure system bringing rainfall to central Queensland and hoped 2008 would be the year. News that the birds had arrived came just weeks later. Rainfall around St George, 435 km west of Brisbane, was spilling into the Balonne River and flowing into the Narran. Geologically, the Narran ultimately meets the Barwon River, which flows in to the Darling, but no-one can recall when the system last flowed that far.

By early March, water in the lakes had reached a depth of more than 60cm, fed largely by the Queensland rains and boosted by local downpours. Dozens of waterbird species were using the site, and many were breeding. Narran is particularly suited to ibis, and colonies of all three species – glossy, white and straw-necked – were there. Most were straw-necked ibises in a massive colony supporting a total of 70,000 pairs.

“I didn’t think Narran would ever see this again,” Kate says. “Given the amount of water taken out of the system by irrigators upstream, and the fact that the birds need a certain minimum amount of water and need it to be maintained for a certain period of time for a certain depth under the nests, I didn’t ever think we’d get enough flow for the birds to breed successfully.”

Just before Easter, however, the water level in Narran began to drop rapidly and Kate feared it might trigger a mass abandonment of chicks. In the boom-bust world of semi-arid Australia, such events are not unusual. Birds have evolved to breed at these sites mainly because the water offers protection from land predators. If it falls, adults won’t risk the exposure to predators and will abandon eggs and chicks. But on this occasion, there were concerns that mass abandonment of the site would have a severe impact on the straw-necked ibis population. Scientists and NSW National Parks and Wildlife officers who manage the site decided intervention was necessary. Ibises are thought to live for only 8-10 years and for many of the nesting adults at Narran, this event might be their only opportunity to breed.

With the looming catastrophe of at least 30,000 dead chicks as their motivation, the Narran Lake management team decided to find more water to top up the system. In an historic deal brokered largely by the NSW Department of Environment and Climate Change (DECC), the Murray-Darling Basin Commission agreed to fund the $2 million acquisition of 11,000 megalitres of water extracted upstream from the Narran and stored on a Queensland cotton farm for irrigation. Peter Terrill, a senior wetlands and rivers conservation officer with DECC, who has been reporting widely on this event, says the property owners showed keen interest in the environmental use of their water, and asked for regular updates on the plight of the colony. The Narran water purchase ultimately rescued three-quarters of the chicks in the threatened colony. But the need for such a measure has raised further questions about  water management in Australia’s inland river systems.

The concept of the environment being allocated a portion of the water used in rivers – an environmental flow – emerged during the mid-1980s. Management plans for NSW’s regulated rivers now allow for environmental flows, intended to maintain the functions of natural ecosystems. Professor Richard Kingsford, of the environmental science department at the University of NSW, says that in reality, environmental flows down regulated systems too often are whatever water is left after irrigators have taken their cut. It’s widely acknowledged that the water resources of most inland rivers have historically been over-allocated and politically mismanaged. But there is now growing support for governments to buy back licences that allow commercial extractions from these rivers and use them to increase environmental allocations.

Richard has been studying Australia’s inland rivers for 20 years and says that the impact of rising water extractions during that time is clearly evident. “The major change I’ve seen is that the floods on the regulated rivers just aren’t coming as often as they used to and they’re not as big as they used to be,” he says, adding that this has reduced the capacity of ecosystems supported by these rivers to bounce back after periods of drought. The environmental impacts are already evident.

“Our research has found that most waterbird species are declining [in Australia], and that is mainly because the major habitats in the Murray-Darling Basin have been severely affected by having fewer floods, which is basically due to more water being taken out upstream,” Richard says.

Other signs of large-scale ecological problems include the widespread death of river red gums throughout the regulated river systems. “These are the plant equivalent of the canary in the coalmine,” Richard says, explaining that dying red gums indicate far-reaching ecological problems. “We know that if they don’t get a flood frequently enough they will start to die. And you can see ‘death lines’ of trees along some river systems where floods have historically reached but no longer do.”

It’s not only plants and animals that suffer from the declines. There are potential socioeconomic implications for the towns dotted along Australia’s inland rivers, as well as complex cultural and heritage issues. Evidence of indigenous occupation is plentiful throughout these systems: from 10,000-year-old stone fish traps on the Barwon near Brewarrina to the remains of shellfish, birds and fish in huge middens around Narran Lake, where it’s believed Aboriginal people have utilised the area’s natural wealth for more than 40,000 years.

Along the Darling there are various indigenous groups with deep cultural and spiritual ties to the river system. In fact, most people in these extreme inland environments feel an intense connection to their rivers. Apart from a brief stint overseas after she left school, Mog Davies has spent her entire life under the influence of the Darling River. She grew up on a property fronting the river, south of the far-western NSW town, Wilcannia. For the past 14 years, she and partner Mark Etheridge have owned and managed Kalyanka, a 50,000 ha grazing run that hugs the Darling for 25 km east of Wilcannia.

As a child Mog spent countless hours on the river, as her own kids, Clancy and Lily, now do. “It was an exciting place to grow up and I loved it,” she says, adding that her children already share her strong connection to the river. “I think a lot of it comes from an acceptance of the environment around you. Out here, it’s all heat and hardness and then good times and you just have to accept it rather than try to manipulate it – and it’s the same for the river. Most people think of a river as the water running through it and the banks on either side. But it’s much more than that – it’s the whole system that goes way out beyond the river.”

Mog says it was unusual for the Darling to be empty when she was growing up. Now the riverbed is regularly exposed and the summer blooms of blue-green algae, once unheard of, have become commonplace. And yet, when it’s flowing, the river still exerts a calming and relaxing influence on both the people and animals that live near it.

“It’s a life support in an environment like this,” Mog says. “The connection is instinctive and it’s those same instincts that I think make us feel uneasy about it being threatened.”

Source: Australian Geographic, Issue 91 (July – Sept, 2008)