WaterNSW has developed a plan it says would see the lower Darling River continue to flow even in a repeat of the river's driest period on record.

The riverbed was completely dry for large periods of 2015 and 2016, destroying crops and forcing farmers to truck in water at huge expense.

The Lower Darling Operations Plan (available here in PDF form) has been developed by WaterNSW to management of the system over the next year.

It considers three scenarios, with the worst dubbed the “Sahara” case.

The Sahara scenario models no flows from the northern parts of the system until all the water is gone.

It found that in this case, the lower Darling would dry up again in December 2018.

But the plan covers ways to maintain flows to the lower Darling under the second scenario - a repeat of the worst drought on record.

It says that if the minimum amount of water let out of the Menindee Lakes into the river was reduced, water was stored in the lakes more efficiently and block banks were built to serve as temporary weirs, a repeat of last time could be avoided.

“Worst case scenario is we cut off the Lower Darling supply to maintain supply to Broken Hill, under extreme circumstances,” WaterNSW spokesperson Tony Webber said.

“We've got sufficient water there we believe to maintain that supply to Broken Hill to April or May 2019, emphasising that that is beyond the scheduled completion of the [Broken Hill] pipeline project.”