Water flows at key sites in the Murray-Darling Basin are the same or worse than before the Basin Plan was implemented in 2012, according to a new report.
The report, compiled by the Wentworth Group of Concerned Scientists, evaluated whether environmental water recovery had led to increases in river flows at two locations: Chowilla and Wilcannia.
Chowilla was chosen as an indication of the volume of flows to South Australia and the health of the Murray River, while Wilcannia was seen as indicative of the health of the Barwon-Darling system upstream of the Menindee Lakes.
The scientists found that despite 2016 GL of water being recovered for the environment (63% of that envisaged under the Basin Plan) at a cost of $8.5 billion, environmental flow targets set by the Murray-Darling Basin Authority (MDBA) had not been achieved.
Excluding natural flood events, annual average flows were found to be 40% to 60% smaller than expected under the Basin Plan. This is despite the period from 2010 to 2018 being relatively wet.
“In general, observed flows are similar to or less than the baseline (pre-Basin Plan) model results, revealing that instead of an increase, there has actually been no improvement or even a decline in water flows since the implementation of the Basin Plan,” the report said.
A fundamental element of the Basin Plan is to reduce over-extraction and ensure water remains in the river system to protect the environment.
The Basin Plan established 3200 GL of water needs to be returned to the system per year to achieve this. However, the Wentworth Group said this figure is not agreed upon by the scientific community.
“The gigalitre value is heavily disputed by independent scientists, including the Wentworth Group of Concerned Scientists, who generally evaluate that the number should be well above 4000 GL,” the report said.
Why are the water flows low?
The scientists said several factors could have contributed to the apparent failure of water recovery efforts to boost river flows.
This includes the fact that under current New South Wales water sharing rules in the Barwon-Darling, additional environmental water in the river means irrigators have greater opportunities to pump environmental water legally.
This is because pumping rights are linked to river flow rates, and there has been no adjustment to these pumping flow rates after environmental water has been purchased.
“This means that water that should have been left in rivers, for environmental purposes, can be extracted from the river for consumptive use,” the report said.
“Protecting these environmental flows across borders is an essential step in improving the health of the river ecosystems, as well as providing tax payer value for money for environmental water purchases.”
In a response to the report, the MDBA said eight years’ worth of measurement was not long enough to draw statistically significant conclusions.
“Six years into implementing the Basin Plan it is not expected that flows across the Basin would fully reflect Basin Plan modelling,” the MDBA said.
It said the “next stage” of the Basin Plan will involve working with southern basin states to overcome barriers to water delivery, and making sure environmental flows and low flows are protected in the north.
“Most of the water that needs to be recovered to return the system to a sustainable footing has been achieved, and now changes to the rules about how water is managed are needed,” the MDBA said.
“This is the next stage of Basin Plan implementation.”
Read the Wentworth Group’s report here.
You can find all our Murray-Darling Basin coverage here.