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Murray-Darling future grim, says report

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Climate change

Murray River

The Murray River in South Australia, well below the waterline.

Credit: iStockphoto

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The future of Australia's threateningly parched Murray-Darling Basin is looking grim, according to a rigorous assessment of the anticipated effects of climate change in the area.

The Murray-Darling Basin Sustainable Yields Project - led by the CSIRO - has used 111 years of daily climate data to model four future scenarios for the availability and use of water in the basin, an area used to grow much of our nation's food and that is home to many endangered native plants and animals.

"We are facing a critical situation in the Murray-Darling Basin after years of over-allocation and drought and in the face of climate change,” said Penny Wong, Minister for Climate Change and Water.

The project has found that today's agricultural activities and water sharing practices in the Basin have caused water to stop flowing through the mouth of the Murray River a whopping 40 per cent of the time. The researchers predict this will be exacerbated a further 24 per cent by the year 2030, under the effects of climate change.

And it is not irrigators or other water users in the region that will suffer most from future climate impacts, the researchers say. It is the environment that will bear the brunt of the assault, taking up to a 20 per cent hit in terms of reduction in water flows.

At particular risk are the Basin's 30,000-plus wetland habitats, 15 of which are listed as Wetlands of International Importance under the Ramsar Convention. Many of these wetland systems rely on natural flooding events to support life.

But the flow of the Basin's rivers has changed through the use of dams and weirs. Compounded by the effects of a decade of drought, this means flood volumes have been greatly reduced - the average annual flood volume is now less than a quarter of what it once was.

The wetland habitats, particularly in the Lower Lakes and Coorong regions, are now drying out beyond the point of saving, and in the future will receive even further reduced flood volumes at increasingly sparse intervals.

"The drought has highlighted how far we've pushed some of these ecosystems…but even when the drought breaks there's going to be an ongoing challenge to provide secure, safe water in a healthy environment unless we make some changes," said lead author of the Project's report, Tom Hatton, Director of the CSIRO's Water for a Healthy Country Flagship in NSW.

His team's research also finds groundwater is being used at an unsustainable rate in many areas of the Basin.

The good news, however, is that the report clearly outlines the most critical areas and issues in the Basin that require attention: "[I]t's absolutely something that is fundamental for us to be able to go forward as a nation and plan a reallocation of water to our rivers," said John Williams, from the NSW Natural Resources Commission.

Ken Mathews, CEO of the National Water Commission in Canberra, agrees. "In the past Australia hasn't managed the Murray-Darling system as well as we could because we haven't properly understood its capacity, its hydrology, the connection between surface flows and groundwater, and the aggregate effects of drought, floods and climate change - as well as the varying demands of each state and territory for its water," he said.

"We now have this information and that's critical to properly managing a river system that supplies at least 40 per cent of Australia's agricultural production. We can now better understand the possible effects of climate change on water availability in the Basin and plan for its impacts."

The findings can be used to guide future government policy on Basin water use, and have prompted the similar analysis of some of Australia's other major river systems, he said.

So far the Rudd Government has committed $3.1 billion towards buying back water rights from willing irrigators in order to return any available water to the Basin's rivers and wetlands. It has also allocated funding towards Basin projects "that improve water efficiency and use, and assist irrigation communities to adjust to a future with less water," said Wong, who anticipates the Sustainable Yields Project to influence the development of a new Basin-wide plan, scheduled for 2011.