Ongoing water releases from the dam together with downstream tributary inflows are seeing major amounts of water flow through the Lachlan system creating minor to moderate flooding.

Lachlan Valley Water chair, Tom Green, says what we are now seeing is a problem which would have been averted with a higher dam wall.

"The minor to moderate flooding around Forbes and downstream from Jemalong Weir will cost this valley millions of dollars, with some farmers suffering massive losses of cereal crops and pasture, and there will also be closure of roads and damage to them," Mr Green said.

"The is a strong possibility of further heavy rainfall which could lead to substantial flooding and damage during the remainder of Spring which would have been avoided if Wyangala Dam wall is raised.

"The raised dam would have averted this flood but still provided the important environmental water needed with a low to moderate flood for landholders in the lower Lachlan all the way to Oxley, as well as the Great Cumbung Swamp and other wetlands in that area," Mr Green said.

"There are expected to be 277,000 ML of translucent environmental flows past Brewster Weir by 12 September, and by late September the total translucent flows may reach the 350,000 ML annual limit, which is a great result for the environment and lower Lachlan graziers," he said.

"Translucent flows include dam releases and tributary inflows below Wyangala dam and would still have occurred if the dam wall was raised," Mr Green said.

The Wyangala Dam Wall Raising project is expected to increase the dam's capacity to hold an additional 650 gigalitres, which will increase capacity by 53 per cent.

The proposed project will see the dam wall height raised, which will increase the Full Supply Level by 10 metres.

"The NSW Government needs to expedite the investigations required to construct the higher dam wall, complete the necessary studies and get the machinery started to construct a project which will be a big win for the Lachlan Valley and its people," Mr Green said.

"We saw the massive damage in 2016 when the river flooded, and five years on we are seeing similar damage once again."

"There have been some concerns raised about less flooding in the lower Lachlan if the dam wall is raised but we're seeing minor flooding at Booligal currently, as a result of translucent flows being released under the environmental flow rules, and inflows from the Belubula and Boorowa Rivers plus other downstream tributaries, which will still occur if the dam wall is raised," Mr Green said.

"We fully support providing water to the wetlands of the lower Lachlan and what is being proposed should provide positive outcomes for all water users and the wider community."

This follows on from indications by the NSW government that it is unlikely that the business cases for its three dam projects, Wyangala, Dungowan and Mole River, will be released to the public - keeping stakeholders in the dark.

The reason given was that they contain detailed market and Cabinet-sensitive information that is subject to strict confidentiality requirements.

A Department of Planning, Industry and Environment stated where relevant, some aspects of a business case could and would be included in the Environmental Impact Statement (EIS), which will be placed on public exhibition for at least 28 days as required by the DPIE.

Mr Green said their expectation was that the business case would be made public.

The full story on the business case can be found on the Forbes Advocate's website.