TAMWORTH water director Bruce Logan confirmed Chaffey Dam would run dry by June 2020 if no actions were taken.
But Mr Logan said the city would have a supply well after then thanks to the temporary weirs in the Peel River and Dungowan pipeline.
The state government recently announced an emergency windfall of $39 million for the Chaffey to Dungowan pipeline with a hope to finish the project by March 2020.
"Without any action Chaffey Dam would be, relatively speaking, empty by June 2020," he said.
"The same modelling says ... temporary weirs and the connection of the weirs to the Dungowan pipeline, that says Chaffey Dam won't be empty until March 2021.
"So we would think with the construction of that pipeline we would see that March 2021 deadline extended further away."
Mr Logan said those estimates were based on the pipeline being constructed in a pretty quick manner.
"At this stage, Water NSW are saying they will have that pipeline installed by the end of March and I have no reason to doubt they won't be," he said.
However, day zero was approaching other regional towns like Dubbo more rapidly than Tamworth, according to Water NSW modelling.
And Mr Logan said the council would keep a close eye on their responses.
"I think we are better prepared than most regional centres in inland NSW, only because we have had some experience with drought previously," he said.
"We never know everything, so we will continue to see what we can do."
It comes as the council announced the city would move to level 5 restrictions on Monday and implored people to reduce the daily water use to 150 litres per day.
The council has also begun a review of its local environment and development control plans in a bid to find more ways to increase water sustainability in the future.
Measures could include the mandating large rain water tanks or grey water systems in new residential developments.