A panel of eminent scientists will examine whether diverting water from the Murray-Darling basin for irrigation caused the mass fish deaths that have shocked Australians over the past few weeks.
The group, convened by the Australian Academy of Science following a request from federal Labor leader Bill Shorten, is chaired by Professor Craig Moritz and includes experts from Canberra, Sydney and Melbourne.
It will examine how the recent mass fish deaths occurred and "whether water diversions and/or water management practices in the Murray-Darling system have caused or exacerbated the scale of this disaster".
The panel will also look at the impact of chemicals, fertilisers and climate change.
The expert's report could support policy changes aimed at improving the health of the river system. It will be made public once it is handed to Mr Shorten by February 10.
The federal government has launched a separate review into why an estimated million fish died along the Darling River at Menindee in NSW's west earlier this month.
It will also analyse how future deaths can be avoided within the parameters of the Murray-Darling Basin Plan.
That report is due by February 20 with the final findings to be handed down the following month.
The NSW government on Tuesday confirmed another kill event with thousands of fish dying along the Macintyre River in the north of the basin.
Western NSW mayors were in Sydney on Wednesday to discuss the Murray-Darling crisis.
Balranald Shire Council's Labor mayor Alan Purtill said Regional Water Minister Niall Blair had been invited to the meeting with councils and water authorities but didn't appear in person or dial in.
"We've got real problems that need to be fixed and I known the people of Balranald are going to be very disappointed," Mr Purtill told reporters on Wednesday.
Brewarrina mayor Phillip O'Connor said his council had put in a lot of work to convey their message regarding the "mess of our river systems".
"It's an absolute joke what our communities have to put up with," he said.
"This is a big drought - but it's not the whole fault of the drought.
"If Sydney Harbour was dried up like our rivers could you imagine the uproar?"
Mr Blair said the western councils were told from the outset a senior member of his team would attend on his behalf.
"A very productive meeting was held today with all mayors expressing their viewpoints and practical solutions canvassed, which my office and agencies will explore," the minister said in a statement.
Mr Blair noted that he met the region's councils in Menindee a fortnight ago and was scheduled to attend the Western Division Councils conference in Bourke in late February.
Australian Associated Press