Knee-deep in green water and cradling dead cod, two outback blokes' emotional pleas on Australia's water policy have gone viral.

Key points: Locals are locking horns with the State and Federal Governments over the two mass fish kill events

Locals are locking horns with the State and Federal Governments over the two mass fish kill events NSW Minister for Primary Industries Niall Blair has received death threats over the disaster

NSW Minister for Primary Industries Niall Blair has received death threats over the disaster A viral video featuring Menindee locals has so far had 2 million views

In a Facebook video posted last night, which has accrued more than 2 million views, Rob McBride and Dick Arnold were filmed standing in the Darling River at Menindee, with one saying he "feels like crying".

A toxic blue-green algae outbreak that robs the water of oxygen killed up to a million fish in the river this week, the second such incident in a month.

With people blaming the disaster on Government mismanagement of the river, NSW Minister for Primary Industries and Regional Water Niall Blair has received threats via social media.

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Locals say Mr Blair has no respect for the river.

"This is bloody disgraceful, this is the most disgusting thing I've seen in my life," Mr McBride said.

"This has nothing to do with drought, this is a man-made disaster brought to you by the New South Wales Government and the Federal Government."

That fact is disputed by the NSW Government, but more on that later.

In the video, Mr Arnold surveys the murky waters, which are dotted with floating fish that suffocated during the bloom.

"It's Australia, we're not bloody fourth-world, fifth-world country for Christ sake," Mr Arnold said.

"It makes me feel like crying."

Blame game over water management

The Federal Department of Environment and Energy said the crippling drought conditions in the area had affected water temperatures in the river and sparked the algal bloom.

A spokesperson yesterday said rain was the only thing that could flush the river out.

However, that is disputed by Mr Arnold and Mr McBride and progressive thinktank the Australia Institute.

"The $13 billion Murray Darling Basin Plan is failing," the Australia Institute said.

"[This is] a preventable environmental catastrophe."

The institute's senior water researcher Maryanne Slattery said although the Government was blaming drought for the fish kill, cod over 80 years old survived several droughts and algal blooms in the past.

South Australian Centre Alliance senator Rex Patrick agreed, and laid into the federal and NSW governments over inaction.

"The Darling River is going into cardiac arrest and both the governments are asleep at the wheel of the ambulance," the senator said.

Senator Patrick urged the State and Federal governments to allow water being held in nearby dams to flow down the river system to meet "basic needs" of humans and livestock.

A pile of dead fish that have been removed from the river at Menindee. ( Supplied: Rob Gregory )

NSW Minister for Primary Industries and Regional Water Niall Blair said the only fix for the algae was rain.

He said cyclones and seasonal wet weather, particularly in Queensland, would typically cause water to flow through the Menindee lakes and down the Darling River.

"We can't make it rain … I can't fill the rivers up if the rain isn't falling," Mr Blair said.

The NSW Irrigators Council, a non-profit body representing the irrigation sector, emphasised the water just "isn't there for anyone" and also took aim at MPs trying to "raise their profile by allocating blame".

The CSIRO said increased river regulation and restricted flows over past decades had seen the number of algal blooms increase in the Murray-Darling Basin.

"It's hard for me to comment on government policy but you would like to see regular flows occurring so you can get flushing of the system," senior principal research scientist Grant Douglas said.