An Upper House inquiry has found the NSW government has not demonstrated that raising the Wyangala Dam wall is a cost-effective or sustainable solution for achieving a reliable water source for the Lachlan Valley.
The finding was released in part one of a two part report from the inquiry, which was tasked with looking into the rationale and impacts of new dams and other water infrastructure.
Part one of the report examines the proposed raising of the Dam wall, while part two will examine the other projects investigated, including Dungowan Dam, Macquarie River storage and Western Weirs projects.
On the raising of Wyangala Dam, chair of the committee undertaking the inquiry, Greens MLC Cate Faehrmann said "the Minister for Water committed to this project without a business case or environmental assessment".
"Two years later we still don't have either."
Ms Faehrmann said the committee heard from many witnesses about the negative impacts of dams on downstream communities and ecosystems, with the threats posed to internationally significant wetlands and threatened bird species particularly compelling.
The project aims to increase the dam's storage by 53 per cent, which the government has said would create capacity for an additional 650 gigalitres.
However, the report found that the annual yield available as a result of increasing Wyangala Dam's capacity by 50 per cent would provide only a 21GL increase in water security.
The project was part of the $1.1billion dam building package and was estimated by the government to cost $650 million, however subsequent estimates reported in the media have been as high as $2.1billion.
Ms Faehrmann described the evidence of a potential cost blowout as "concerning".
She also stated alternative options to addressing water security were not given due consideration before the government announced it would raise the wall.
There were two Dissenting Statements attached to the report, including one from National party member Ben Franklin and Liberals Shayne Mallard and Catherine Cusack, and one from Ms Faehrmann.
A spokesperson from Minister Pavey's office said the government will review the draft report and consider its recommendations in due course.
"In the meantime we will continue on working towards improving water security for the Lachlan Valley and regional NSW," they said.
Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: