“I’m responsible if it goes wrong – the responsibility resides with me,” the agriculture and water resources minister told reporters in Canberra.
Mr Joyce was responding to confusion, even in government ranks, about how much power he will wield over the Murray-Darling Basin and how much say his new assistant minister Anne Ruston will have on water policy.
The minister has now clarified "conjecture" around his role, saying he will have the lead on most water matters, except for environmental flows around the basin, because it was never in the agriculture portfolio anyway.
"But all the functions away from that are with the minister ... who is me," Mr Joyce said.
That means government buybacks of water entitlements are his department's responsibility.
As for the Commonwealth Environmental Water Holder, which manages the water the government buys back, Mr Joyce said it made "abundant sense" for the agency to be administered by the environment department.
In any event, a minister had very little influence over the statutory body, he said.
Mr Joyce is planning to tour the basin and conduct a review of its plan.
"This is easy knitting to pick up, because it's a job I've done before," he said referring to his time as water spokesman for the coalition in opposition.
Labor seized on the fact that bottom-of-the-basin Liberal Jamie Briggs will have ministerial responsibility over the Environmental Water Holder.
"This has become ridiculously chaotic," opposition agriculture spokesman Joel Fitzgibbon said, calling on Mr Joyce to release a letter from the prime minister stipulating his specific duties.
"Today people don't know who they should be talking to (about water)."