Out of sight out of mind - floodplains

Posted 7 March 2008

Richard Kingsford
University of New South Wales

"Out on the plains the brolgas are dancing", starts the old Australian Christmas carol. But the dance floor is shrinking: bit by bit, it's being cut away.

Not that you would think so right now if you visit the inland rivers west of Bourke, thanks to drenching rains up north. Fly over the Paroo River, for example, and you'll see that the main arm of the river has overflowed. Breaking away from it are myriad intertwined channels, all joining and slowly spreading through lignum swamps and other wetlands to form an astonishing million ha of floodplain. It's 40 kilometres wide in places - hardly "some old bridle-track", as Henry Lawson described it when he saw it in dry times.

Floodplains vibrate with life during floods. Water-holding frogs emerge from their underground sacs to lumber around and eat anything that moves, even their own kind. Plants sprout almost miraculously from seemingly lifeless soil. Crustaceans and insects multiply exponentially, with generation times measured in weeks. For fish such as silver perch and yellowbelly, the floodplain opens up a smorgasbord. In turn, they and their young will feed vast numbers of cormorants and pelicans: on one of the large Currawinya Lakes on the Paroo right now there's already a pelican colony of about 15,000 pairs. These are our rivers and floodplains, beating to the rhythm of our erratic climatic La Nina and El Nino cycles.

But the river drought has not broken on the floodplains of the regulated rivers, like the Murray and the Macquarie. Most dams on these rivers, west of the Great Dividing Range, are partly filled by water that once replenished the floodplains but is now stored for irrigation. These southern floodplains are dying. More than three quarters of the river red gums along the lower River Murray - many of them hundreds of years old - are either dead or poorly due to increasing salinity and lack of water. All this is known, and governments are striving to deal with over-allocated rivers. The NSW Government is meeting its laudable pledge of $105 million to buy back water for the environment. But this is only half the story, because the focus is on the rivers themselves and not their floodplains.

Thousands of years of sediment dumped by flooding rivers makes for extremely fertile plains - great for irrigation. While water extraction from rivers is ever-more tightly monitored, metered and costed, few rules or regulations govern what happens out on the floodplain. They are ripe for clearing and laser-levelling and the construction of intricate systems of channels and levee banks to control, channel and divert water for flood irrigation.

An Australian river is a very different beast to an English River. Yet until relatively recently, the floodplain and its channels scarcely rated a mention in water management legislation inherited from our British forebears. It was not part of the river and so not subject to any laws or regulations. In NSW, the government water agency had to designate a floodplain for it to command any status. Despite inclusion of floodplains in the NSW Water Management Act 2000, they are still managed under the archaic 1912 Water Act.

Using satellite photographs and visiting many sites on the ground, our research team has identified more than 2,000 km of earthworks - levees and channels - on the Macquarie floodplain. These structures alter the natural cycles of the floodplain and its organisms, including the internationally renowned Macquarie Marshes. River red gums and black box eucalypts have had their connection to the river severed and many of them are parched and dying. The Macquarie is not an isolated example. Take a digital wander on Google Earth - the Outback is no longer out of sight of city eyes - and visit the floodplains of other rivers of the Murray-Darling: the Border Rivers, the Condamine-Balonne, the Darling and the Gwydir. Most of the levees and constructed channels are legal although often guidelines to maintain free passage for floods have been breached.

So why worry? For the first time, there is clear acknowledgment by all governments that the rivers of the Murray-Darling Basin are in serious trouble. The Murray-Darling Basin Cap, the historic decision to hold diversions of water from rivers at 1994 levels of development, was supposed to halt degradation and apply to the whole river. But, of course, floodplains went missing. A channel can conveniently intercept water flowing across the floodplain - water not monitored, not metered, not accounted for, not paid for and taken from the environment and from downstream environment and graziers. The NSW government produced a good floodplain harvesting policy in about 2003, recognising that the Murray-Darling Basin Cap applied to levee banks, but its principles were never implemented. Now a new draft policy may have a grandfather clause, essentially ignoring the implementation of the previous policy decision in relation to the Murray-Darling Basin Cap.

If governments are going to effectively deal with over-allocated rivers, the floodplains cannot be ignored. Right now, the main policy path is to buy back water from the irrigation industry and return it to the rivers. Even this is a problem. Some of the environmental flow to the Macquarie Marshes in November 2005 was reportedly harvested by channels and earthworks before it reached the wetland, an inevitable consequence of a high-flowing river erupting over its banks onto the floodplain. While the earthworks on the Macquarie floodplain may not be illegal, taking part of the share of environmental water is a very different matter.

If they're serious about sustainability and cleaning up the mess we've made of our rivers, Australia's governments must recognise their complexity. They must manage not just the main arteries but all the living tissue of nature they support on the floodplains as well. Good floodplain legislation and regulation is needed urgently, while we still have time to ensure that there is enough water to keep those brolgas dancing.

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