Current implementation of the Murray-Darling Basin plan could leave the vital water resource in a worse position than before the rescue strategy was developed, an inquiry has been told.
Former Murray-Darling Basin Authority official David Bell offered his grim assessment in a written submission to South Australia's royal commission into the basin plan.
His submission came as he gave evidence at the commission's opening public hearing in Adelaide on Monday.
Mr Bell said the basin plan, which returns a level of water to the river system to ensure its environmental health, was a "quite remarkable" piece of natural resource management.
"However, I am very concerned about how the plan is being implemented and that it could very likely lead to the basin being in a worse position than prior to the plan," he said.
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Mr Bell joined the authority in 2009 and retired as director of environmental water planning in November 2017.
In his evidence, he also told how, quite early in his employment, he had been given a half an hour to come up with an estimate of the amount of water that should be recovered to sustain key sites along the basin.
His estimate was "in the vicinity" of 4000 to 4500 gigalitres.
But he said it became known around the authority that the final number "needed to start with a two", for the plan to be acceptable to all states with the authority ultimately settling on original recovery target of 2800gl.
In regard to the operation of the plan, Mr Bell said there had been a failure to recover "real water" through buy-backs and efficiency measures.
"I think some of that water is fictitious, which undermines the water rights system," he said in his submission.
Opening the hearing on Monday, commissioner Bret Walker said a bid by the federal government to stop current employees of the basin authority from giving evidence would not stop a full investigation into water use.
Mr Walker said while it was not his place to comment on the High Court action by the government, the commission would fulfil its terms of reference.
The focus of his inquiry was whether the basin plan was lawfully made in every respect, and whether or not it had been lawfully amended.
"Any failure by the commonwealth, by the basin authority, to participate in the proceedings of this royal commission does nothing to remove that question from public controversy," Mr Walker said.
The commission was established in January 2018 to inquire into the operations and effectiveness of the basin plan after widespread reports of water theft.
Its final report is due by February next year.
