A report has revealed 20 per cent of river water expected under the Murray-Darling Basin Plan did not flow in the rivers of the basin between 2012 and 2019.
The report, completed by the Wentworth Group Of Concerned Scientists, looked into whether water reforms by the Australian Government had resulted in the flows needed to improve river health.
The report authors say this water should have been available to boost flows in drought-stricken rivers, improve water quality, provide habitat for fish, birds and other species, and support the health of internationally recognised wetlands, such as the Macquarie Marshes, the Riverland and the Coorong.
The report measured how much water actually flowed past 27 river gauges across the basin compared to how much was expected to flow at these gauges, under basin plan modelling since 2012.
This modelling has been criticised in the past, particularly during the South Australian Royal Commission.
After accounting for drought and the variable amounts of water available in each year, the valley by valley assessment found more than 1200 billion litres failed to reach the South Australian border every year.
The Wentworth Group has put the shortfalls down to a number of reasons, including changes
to rules and protections of environmental water, higher-than-expected volumes evaporating or seeping into channels, the possibility that not as much water has been allocated for the environment as was expected or model errors.
The Murray-Darling Basin Authority acknowledged the report's findings at a meeting held on September 2 and 3.
“We always welcome the scientific community's views about where things can be improved and will continue to engage in joint efforts to make the basin plan better,” the authority's communique said.