Poor water management and excessive extraction are the primary cause of declining flow and the poor state of Australia's iconic Darling River, a new study has found.
Researchers from The Australian National University (ANU) and UNSW Sydney investigated the effects of both climate change and water resource management on the Darling River over the last 40 years.
Their study, published in the prestigious journal Philosophical Transactions A of the Royal Society, found the principal cause of river flow decline on the Darling River, known by First Nations people as the Baaka River, is not due to a drying climate but rather ongoing and "large-scale" water management failures.
"Our analyses separated the effects of declining flows in the Darling River due to long-term meteorological trends from other factors, such as increased water extractions," study lead author ARC Laureate Fellow Professor Quentin Grafton, from ANU, said.
"We found that more than half the decline in river flows on the Darling River over the past 40 years was due to factors other than higher temperatures or less rainfall.
"The Darling has had high rates of water extraction for decades -- driven by water allocation and provided by 15 main channel weirs and over 1,000 small weirs along its 1,000 km length, including upstream.
"Our principal finding is that much of the river flow decline on the Darling River over the past 40 years has not been because of climate change but almost certainly a result of increased water extractions.
"Further evidence in support of this conclusion can be drawn from the large, unmetered, and possibly increasing, water extractions associated with floodplain harvesting in the order of hundreds of billions of litres per year in the northern Murray-Darling Basin, some of which may be illegal."
Study co-author Professor Richard Kingsford, Director of the Centre for Ecosystem Science at UNSW Sydney, said the findings show that while climate change was clearly happening it can't be used as an "excuse" for the negative impacts poor water management was having on the Darling River. But importantly, the poor state of the rivers was due to systemic problems in over allocation of water.
"Our point isn't that climate change is not happening. It's here, it's now and is global in its impacts but the story of fish kills at Menindee and declines in health of wetlands of international importance like the Macquarie Marshes was due to decreasing river flows," Professor Kingsford said.
"Climate change shouldn't be used as a 'get out of jail card' or treated as an 'act of God' to excuse bad decision-making and poor planning decisions.
"Much can be done to adapt to both droughts and floods and to reduce both the risks and the consequences to people and the planet from extreme weather event and protect our biodiversity and the people that rely on rivers.
"We have no excuses for claiming that climate change is primarily or solely responsible for declining flows on Darling River when it's not."
In highlighting the importance of the findings, Professor Grafton said: "We need to reduce water extractions and reallocate water on this iconic river to ensure minimum river flows for downstream communities and critically important environments.
"This task is urgent if we, as a nation, are to achieve what we agreed to with the Basin Plan a decade ago; healthy sustainable working rivers."
Read the full study online.