The NSW government has strongly committed to building and expanding dams in a bid to improve water security during dry times.
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One of its main projects, raising the Wyangala Dam wall by 10 metres, is estimated to yield on average an extra 21 gigalitres of water a year for the Lachlan Valley - improving reliability for water users.
Funding of $650 million has been secured, but there are reports that raising the dam wall could cost closer to $2.1 billion.
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An Upper House inquiry into the project has recommended the government investigate alternative water efficiency measures that may be more cost-effective and have less impact on the environment.
Chair of the Upper House inquiry, Greens MP Cate Faehrmann said it was a "dereliction" of the Water Minister's duty not to consider alternatives to providing water security in the Lachlan Valley.
"Just because the National Party pulled this out of the bottom drawer before the last election doesn't mean that it should go ahead at all costs and at the expense of cheaper alternatives," Ms Faehrmann said.
One alternative proposed by the inquiry was upgrading the Jemalong Irrigation scheme's infrastructure.
Jemalong Irrigation is a gravity-fed scheme near Forbes with around 300 kilometres of earth channels, close to 100 members and approximately 80,000 megalitres of water entitlements.
Estimated 15,551ML/year in losses saved
Back in 2009 a draft report for modernising the scheme was prepared by Western Land Planning and it estimated that water losses in Jemalong Irrigation's channel delivery system ranged from 16,425 to 20,617 ML/yr.
One of the options for upgrading the scheme's infrastructure was piping and lining the canals, estimated to prevent 15,551ML/yr in losses and have a capital and 20-year maintenance cost of $106.6 million (2009 value).
Funding for the project never eventuated and Jemalong Irrigation's current chair Nick Turner said since then any infrastructure upgrades had been paid for by the irrigation company themselves.
"I wasn't on the board at the time but I know a material amount of time and investment was put forward from Jemalong Irrigation, including the involvement of a number of external consultants ... to try and secure some of this funding," Mr Turner said.
"For reasons I'm not sure of, we were unsuccessful."
Mr Turner said Jemalong Irrigation was currently undertaking a significant, self-funded refurbishment of the channels - which included reshaping the beds, batters and top of bank using GPS technology to improve efficiency and minimise losses.
"We're also fencing off the channels in some areas, which assists in reducing ongoing maintenance costs and also minimises future biosecurity issues," Mr Turner said.
Jemalong chair would choose raising dam wall
Although Jemalong Irrigation would welcome any government grants to improve their efficiency, Mr Turner said given a choice between piping for Jemalong and raising the Wyangala Dam wall - he would choose Wyangala.
"Holistically the Lachlan Valley is more than just Jemalong Irrigation," Mr Turner said.
"I would support the raising of the dam wall because there's so many wider benefits for all key stakeholders along the river - whilst it may be hard to justify the numbers today, we all have to play the long game and reinvestment into infrastructure is part of that game.
"We also need to remember that the dam wall is due for a safety upgrade with the last quote obtained some years ago amounting to $250M, this cost we will alleviated as the upgrade will form part of the dam wall increase."
Mr Turner said they were also aware that the ongoing maintenance costs involved with a large-scale project like piping Jemalong Irrigation could be too much for the company to bear.
"A large capital investment into a depreciating asset such as a piped scheme will require significant on going maintenance and this annual maintenance would financially destroy a company like Jemalong Irrigation," Mr Turner said.
A spokesperson from the Department of Planning, Industry and Environment said the business case for the Wyangala Dam wall raising will consider a range of options.
They added the federal government had recently announced funding for its Off Farm Efficiency Program and the NSW Government would be working with interested farmers, irrigators and communities on their ideas for improving on and off farm water efficiency through infrastructure.
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