Blog | 1st Feb, 2011

of the floodwaters

The floodwaters surrounding Swan Hill have been devastating for humans, but for more many other plants and animals, they have been a welcome drink.

The floodwaters coursing through the Murray-Darling river system are causing great hardship for local communities as homes and businesses go under. But they are also returning life to the ailing landscape after more than a decade of punishing drought.

River red gum forests along the Murray are awash with a muddy brown tide and the thirsty old trees are drinking deeply. Water birds which nested after the smaller floods last September are now feeding their chicks on the abundant insects, fish and frogs in the floodwaters, and some may be laying a second clutch of eggs. Unfamiliar shades of green spread to the horizon, while lakes and wetlands once dustbowls are glistening with water. Even Lake Albacutya in western Victoria might get a drink for the first time in more than 25 years.

Unlike our cities and towns, Australia’s natural environment thrives on a flood. In fact some plants, birds and animals need them to survive. To give just two examples: the threatened plumed egret only nests and breeds in flooded river red gum forests, and the endangered Murray cod only spawns during floods.

Most native species have adapted to survive the occasional dry spell, or even a ‘normal’ drought. However, the recent drought was not just long. Its effects were made far worse by the fact that most of the remaining scarce flows were diverted for human use – mainly for irrigation. This left the natural environment with far less water than nature intended and stretched its survival capacities to the limit. In the Murray-Darling, bird numbers plummeted by a massive 80 per cent, and old river red gums that had survived many a drought began to turn grey.

So this time around, despite the size of the current floods, nature will take longer to recover. The recent ‘blackwater’ fish kills are an example of why it will be harder for natural systems to bounce back after years of mistreatment.

Over summer, in rivers in the southern basin, thousands of native fish have been found floating dead in dark-coloured flood waters. Such events can happen naturally, but this time they are at least partly a result of human intervention.

To explain – in dry years leaf litter and other plant debris accumulates on floodplains, then gets washed away when the waters rise. But during the drought, to meet the demands of irrigators and other water users, not even small floods were allowed to flush out the river systems, so the debris built up year after year.

Now, when we get a big flood, all that carbon-rich plant material is rotting in the water and using up the oxygen fish need to breathe. In the affected areas, fish populations that have shrunk during the drought face another devastating blow – just when they would otherwise begin to breed and multiply.

Regardless of such problems, these exceptional floods have given life in the basin a reprieve. But like human communities, how quickly and successfully nature rebuilds will depend on what happens next.

With dam levels high, the prospects for the next year or two look brighter. However the long term trends driven by climate change will inexorably push us back into drought, if not sooner then later. Knowing this, we have a chance now to prepare, and make sure we don’t let the rivers ever go back to the awful state they were in just a year ago.

As well as tackling the causes of climate change, we need to improve the way water is shared in the Murray-Darling Basin. Rivers and wildlife must get a fair share of water during the dry times as well as in the wet.

Some see the floods as an excuse to yet again delay the difficult job of water reform, but this is actually the best time to instigate change, while the immediate pressure of water shortages has eased, and plentiful water becomes less expensive to buy back from willing sellers. Knee-jerk calls for more dams are misguided and short sighted. As we saw in Brisbane, even the biggest dams won’t stop a powerful flood.

The Murray-Darling Basin Plan provides a once in a generation opportunity to get our water use onto a more sustainable footing. Returning a fair share of water to the environment will allow the flourishing of life triggered by the floods to continue. It would also reduce the number of blackwater fish kills in future.

On the other hand, if we continue to drain our rivers for irrigation we can be sure that the water will run out again, and the recovery these floods have triggered will come to an abrupt halt.

This opinion piece appeared on the ABC website on Tuesday, 1 February.