The new interim inspector-general of water compliance faced questions from senators during a parliamentary inquiry, which ended abruptly after politicians engaged in a bitter stoush.

South Australian senator Rex Patrick said as Dubbo's state MP, Mr Grant had supported farmers over Indigenous, recreational and environmental basin communities.

The former deputy premier said he secured $15 million for NSW Landcare and record funding for local Indigenous groups during his time in parliament.

"To say that I preference one group over another I think is extraordinarily unfair given my track record in outcomes for those other groups," Mr Grant told the hearing on Wednesday.

He accused Senator Patrick of looking at comments in isolation.

"If there's any questions of my integrity - you're welcome to raise them - then you better come with proof."

Nationals senator Bridget McKenzie leapt to Mr Grant's defence, saying she was offended by the line of questioning.

"Why do you preference yachties in South Australia over food production?" she asked Senator Patrick.

In a testy exchange, he argued all water users across the basin should get their share.

Senator McKenzie, who is a former agriculture minister, believes there is a hierarchy which gives some groups higher importance than others.

Senator Patrick insisted he was reflecting constituents' concerns and giving Mr Grant the opportunity to quash perceptions of bias.

The hearing descended into an ugly shouting match between senators, with Liberal committee chair Slade Brockman calling time on proceedings after tensions boiled over.

Senator Patrick said the Nationals didn't care about water compliance, sparking a furious reaction from Senator McKenzie and her partyroom colleague Perin Davey.

A fired-up Senator Davey said SA had dragged the chain on water compliance, allowing irrigators to take water that wasn't in their account.

"Withdraw that remark, Senator Patrick, or I will make the same statement about all South Australians," the NSW senator shouted.

Senator McKenzie also demanded a withdrawal, saying it was an outrageous reflection on her as Nationals leader in the upper house.

"Basically saying that we are corrupt - that's actually what you were saying by that - and it is completely untrue."

But Senator Patrick refused to take back his comment.

"I seem to have touched a nerve," he said.

Earlier, Mr Grant vowed to address the lack of trust and confidence in the Murray-Darling Basin Authority.

"There's suspicion, a lot of finger pointing and everyone is talking about a need for a single source of truth."

"When decisions are made by bodies they're not explaining why. They're certainly not talking to other groups about consequential outcomes."

He said communication would be paramount in boosting trust across the basin.

Australian Associated Press