A damning report into the cause of millions of fish deaths has ignited demands to overhaul state water laws and beef up enforcement in the Darling River system.
The NSW chief scientist and engineer's report warned a repeat of the mass fish kill at Menindee in March was likely amid a drying climate.
Many of the causes of the event, which left an estimated 20 million fish dead, had been well-documented in previous reports but many of their recommendations still had not been implemented, Hugh Durrant-Whyte said.
"This lack of action represents a clear contributing factor to ongoing system decline and fish deaths," the chief scientist said in the report's executive summary, released on Thursday evening.
Professor Durrant-Whyte recommended the enforcement of environmental protections, urging the introduction of legally enforceable obligations and powers to ensure the health of the entire catchment's ecosystem was protected.
Strategies should also be developed to reduce the risk of further mass fish deaths and restore river health, he said.
Greens MP Cate Faehrmann on Friday said the findings warranted an overhaul of the state's water department.
"These terrible fish kills, off the back of the carnage we saw in 2018/19, are clearly a manifestation of the overall degradation of the broader river ecosystem resulting from decades of wilful mismanagement of water in NSW," she said.
Nature Conservation Council of NSW water campaigner Mel Gray said the state had strong laws to ensure the river was looked after before water was extracted, but those laws were useless if they were not put into practice.
Water minister Rose Jackson accepted the report's recommendations and said work was already under way to improve river health.
That work includes water-quality monitoring and more dissolved oxygen sensors.
"We are grateful for the work and insight the local community have put into this report and we remain committed to communicating with openness and transparency with the Menindee community," Ms Jackson said.
Any changes to the management of the Darling River will also impact many of the 2.3 million people living in the Murray-Darling Basin.
The independent authority overseeing the basin's $13 billion management plan in July admitted there was no way it could hit legislated targets for water-restoring measures to be in place by June 2024.
In response, the Albanese government struck a new deal with NSW, South Australia, Queensland and the ACT to ensure water promised under the plan would be returned to the environment by 2027.
Victoria is the only basin state not to sign up due to its government being opposed to water buybacks.
NSW Irrigators' Council chief executive Claire Miller said simply buying water back from farmers was not the best answer and water quality as well as volume should be looked at.
She said the root causes of river degradation needed to be addressed, including the spread of invasive species like carp, obstructions to fish migration and contamination from cold water.
"Instead, we have the federal government now preparing to pour billions more dollars into unnecessary buybacks from farmers," Ms Miller said.