Increasing the capacity of the Central Coast's Mangrove Creek Dam and building a pipeline to connect Upper Hunter Dams are being considered to build water resilience across the greater Hunter region.
Hunter Water is currently weighing up the whether to build a new, small dam in the Lower Hunter, but the option of increasing the capacity of dams beyond the region is also on the table as part of the Lower Hunter Water Plan discussion.
The 190 gigalitre Mangrove Creek dam, located at Kulnura, is already connected to the Lower Hunter via the Hunter-Central Coast water transfer system.
The pipeline was constructed in 2006 when the Central Coast's water supply was at 10 per cent.
About a gigalitre of water has been transferred through the system in both directions in recent years.
Expanding the Mangrove Mountain dam would increase the capacity of the Central Coast to supplement the Lower Hunter's water supply when needed.
The Lower Hunter is not presently connected to the Upper Hunter's water network, however, there are plans to connect it via a pipeline at Singleton.
About $4.3 million was earmarked in the 2018 Greater Hunter Regional Water Strategy to investigate the feasibility of connecting the 283 gigalitre Glennies Creek dam with the 20 gigalitre Lostock dam.
The 750 gigalitre Glenbawn Dam, which is currently at 40 per cent capacity, is the Upper Hunter's major dam.
Glennies Creek and Lostock, currently at 37 per cent and 94 per cent respectively, are secondary sources.
"It's not technically increasing dam walls but it does increase the capacity of those dams," Hunter Water chief investment officer Darren Cleary said.
"Lostock is like Chichester Dam, it's a small dam in a fairly reliable catchment so it spills frequently.
"Glennies Creek is a larger dam with a less reliable catchment so it allows you to push water back up into Glennies and store it so the overall yield of that system increases."
Water NSW's 20 Infrastructure Options Study shows the Glennies Creek to Lostock pipeline could be built to transfer between 7.5 gigalitres per annum to 73 gigalitres per annum.
It would cost between $115 million to $502 million to build.
Upper Hunter Water Users Association vice president Ken Bray said the project was a topical subject of conversation.
"It's very early days but in principle you have to respect the concept," he said.
"Hopefully we will see a bit more work on it in the near future."
Adding to the puzzle is the possibility that the state government may pursue the 450 gigalitre Cameron's Dam near the 1335 hectare Camerons Gorge Nature Reserve between Murrurundi and Scone.
The project, which has the backing of Upper Hunter National's MP Michael Johnsen and his federal counterpart Barnaby Joyce, would cost an estimated $900 million.
Mr Cleary said the project would have major implications for the distribution throughout the Hunter region.
"Broadly, if there is a link between the Lower Hunter and the Upper Hunter, anything that increases the overall amount of water in the system could still benefit the Lower Hunter," he said.