New South Wales is “well behind” on developing crucial water-sharing plans for its rivers and “is unlikely to meet agreed timeframes of 30 June 2019”, putting in doubt its claims that water is being shared fairly between farmers and the environment.

The damning assessment by the Murray-Darling Basin Authority is contained in the December 2018 progress report posted on its website and comes as NSW faces growing questions over whether its rivers are over-allocated in the wake of a big fish kill at Menindee on the Darling River.

Water resource plans, or water-sharing plans, set the detailed rules for sharing water between irrigators and the environment in each catchment. They include rules on how allocations will be made, when irrigators must cease pumping in low flows, pump sizes permitted, and rules for shepherding environmental flows down the river.

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But NSW has failed to submit even first drafts of 12 of of its 20 required plans, including those for major rivers such as the Barwon Darling, the Lower Darling, the Namoi and the Murrumbidgee.

Instead, NSW is operating its rivers under old plans, which have not been accredited.

In particular, the 2012 Barwon Darling water-sharing plan has come in for heavy criticism because it allows irrigators to pump during low and medium flows.

The revelations of NSW’s slow progress come as as low river flows, hot weather and algal blooms in several rivers have caused massive fish kills.

The NSW minister for primary industries, Niall Blair, denied on Tuesday there was a problem of over-allocation in NSW, saying that the primary cause of falling dam levels and low flows was the drought.

“We have water-sharing plans and we are developing and submitting our water resource plans for all across New South Wales to be signed off by Canberra,” he said. “This is not a debate about over-allocation.

“This is a drought. For people to jump on the bandwagon now and point the finger at farmers and tell them they are responsible for this – go and look at the records.

But the water-sharing plans Blair was referring to are incomplete and NSW lagging is far behind other states.

The MDBA said 12 of NSW’s were only at the “preliminary phase” in which NSW outlines its approach to the MDBA. The MDBA rated its level of confidence of NSW meeting the deadline at 30% or less.

“The MDBA remains concerned about the large volume of work that needs to be completed,” the report said. “At this stage MDBA considers that eight of the 20 NSW WRPs are on track for accreditation by mid-2019.

While the authority said NSW was co-operating, it said the state still needed to resolve a number of complex policy implementation issues to enable the accreditation of its plans.

These included floodplain harvesting, water accounting issues and the protection of environmental water in the northern NSW catchments.