The dam projects have split opinion within communities and politics alike.

Although many irrigators argue the dams are necessary to improve water security in dry times, an Upper House inquiry found the cost-effectiveness or benefits of some of the projects were yet to the proven.

Much of the cost-benefit analysis will be part of the business cases, due at the end of 2021.

However, when the Department of Planning, Industry and Environment was questioned on whether the business cases would be made public a spokesperson stated it was "not standard government practice to release business cases for complex infrastructure projects publicly".

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

The spokesperson said 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.

"The Environmental Impact Statements contain detailed information about the benefits and impacts of proposed projects," the spokesperson said.

Lachlan Valley Water chairman Tom Green supports the raising of the Wyangala Dam wall, but said their expectation was the business case would be made public.

"We'd like to see it released to know what potential costs there would be, part of which could be borne by water users," Mr Green, from Forbes, said.

"We would also like to see the benefits of both flood management and water security and what they would look like.

"There's always some sensitivities and I can understand why there could be parts redacted but I would still expect the relevant information to be available."

The water level at Wyangala Dam has increased rapidly this year during a wet winter.

On Wednesday last week the level increased to 101 per cent of capacity with all of the flood gates at the dam opened for the first time in several years.

The Bureau of Meteorology is forecasting a wet spring.

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