Cotton farmers and conservationists are engaging in heated exchanges on social media as the furore continues over the fish kills in the Darling River.

Hundreds of thousands of fish have died in the third kill in less than two months at the town of Menindee in far-west New South Wales.

Agriculture Minister David Littleproud ordered an inquiry into the incident last week.

People in Menindee blame the crisis on cotton irrigators' water use and the Murray-Darling Basin Authority's [MDBA] decision to empty the Menindee Lakes in 2014 and 2017.

Experts say irrigators are taking too much water from the system, and the MDBA has mismanaged water flows which has contributed to the fish deaths.

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Cotton Australia said all major cotton growing valleys in north-west NSW had no water allocated to them this harvest season.

Cotton grower Andrew Watson, from north-west New South Wales, said farmers were fielding abuse in debates online, which he said were based on incorrect information.

"People actually don't know the facts and you know there are plenty of cotton growers who are willing to engage [and] talk about what we do," he said.

"Water is taken under the rules that have been put in place over many years and that's been the frustrating thing.

Debate is raging online about the role of cotton production in the state of waterways in the Murray Darling Basin. ( Twitter )

"We're only following the rules but people are posting on social media that they want to kill us."

Cotton Australia chief executive Adam Kay said growers felt under attack.

"Some of our growers are withdrawing from social media," he said.

"There's so much emotion there and so much ill-informed opinion.

"The growers are feeling quite distressed at the attacks on them when they know they are baseless."

'People are right to be angry': MP

New South Wales independent MP Jeremy Buckingham has used social media to point the finger at the cotton industry.

New South Wales independent MP Jeremy Buckingham used Twitter to target cotton farmers over water use. ( Twitter: Jeremy Buckingham )

He said while it was unfortunate that growers were being targeted online, he understood why people who cared about the Darling River were upset.

He said social media could be controversial.

"People get on there, they get fired up about an issue and they feel like they can lash out but it's important that we build understanding about what's going on."

Mr Buckingham said while people's anger could be misdirected, he still believed the buck stopped with the largest irrigators.

"The biggest water users in the system in northern New South Wales and southern Queensland are the corporate irrigators. We're not talking about 'mum and dad' farms here.

"People are right to be angry, there are a lot of people in southern and western New South Wales who are going to miss out on irrigation because the river has been over allocated in the north."

In an online statement, the owners of Cubbie Station near Dirranbandi have defended the property's water usage.

It said that despite having 22,000 hectares of irrigated cropping fields, no summer crops would be planted this year as there was no water available.

According to the statement, the last time the station diverted water was in April 2017, when 14 gigalitres was redirected.

Concerns for farmers' mental health

Mary O'Brien, founder of the mental health awareness program Are You Bogged Mate?, said many farmers, in cotton and other industries, were being targeted online.

She said she had talked with many farmers who were already struggling with the pressures of drought and were now feeling disheartened by online bullying.

"It is just saddening. I am gobsmacked at some of the crazy comments, the ridiculous comments … it's completely out of control," Ms O'Brien said.

"These guys are struggling already emotionally and financially and this is just the last thing we need.

"The farmers in Australia are just getting absolutely slammed from people with a skewed view."

Editor's note 31/01/2019: This story has been updated since its original publication date of 30/01/2019.