Raising the Wyangala Dam wall should yield an additional 21.05 Gigalitres per year for general security irrigation, a fact sheet released by Water NSW since Sunday's announcement says.
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Federal and State governments have announced they will partner in a $650 million project to raise the wall of the dam on the Lachlan River by 10 metres.
A fact sheet published on the Water NSW website since the announcement says the project will increase the dam's capacity by 53 per cent, providing significant improvement in drought security, flood management and water reliability.
The ability to capture an additional 650 Gigalitres of water will have an enormous impact on the reliability of irrigation water and that will be very welcome, says Lachlan Valley Water's Mary Ewing.
The additional capacity would make a huge difference in extreme situations such as we have just faced: a flood followed by drought.
"900,000 megalitres was released (from the dam) between August and November 2016," Mrs Ewing said. So if a proportion of that volume could have been retained, the Lachlan would be in a much better position this year, when inflows have been extremely low.
Over the past 15 to 20 years the percentage of water allocation that irrigators have been allowed each year has varied greatly, Mrs Ewing said.
There has been no new general security allocation since 2017.
Irrigators can, and do, use water held over from previous years but in the current conditions their access to 43 per cent of that has been suspended.
"This isn't about issuing new irrigation licences," Mrs Ewing said.
"It's not about increasing usage above the existing limit.
"First and foremost it's about the security of town water requirements and other high priority needs, underpinning the community, and then about improving reliability for irrigators."
And with an approximate return of $806 per megalitre at the farm gate, increased security is pretty significant to the regional economy.
That figure, Mrs Ewing explains, is based on Australian Bureau of Statistics data for 2015 / 16 (the most recent figures online) showing Lachlan irrigation production valued at $222,000,000, with the main crops being vegetables, fruit and nuts, and cotton.
According to the NSW Water Register total water usage in the Lachlan (groundwater and surface water) that year was 323,380 ML, of which 48,000 was environmental water.
"At this stage we welcome the announcement, and would like to see that detailed business case proceed as quickly as possible," Mrs Ewing said.
Water NSW gives the estimated timeline as:
- 2020 Community engagement commences
- Year One Concept Design & Environmental Assessment
- End of Year Two Project Determination
- Year Three Detailed Design and Pre-Construction enabling work
- From Year Four Dam construction (two to four years)
The Advocate did ask whether Year One was expected to be 2021, or even 2020, but no further is available at this early stage.
The project includes raising the spillway and intake towers by 10 metres and raising the embankment and downstream rockfall.
