Sugarloaf Pipeline opponents have pounced on statements by a senior water public servant which have indicated that predictions made about water availability might not come to fruition.

Victorian Office of Water chief David Downie was giving tribunal evidence in a freedom of information case in the Victorian Civil and Administrative Tribunal.

Mr Downie said factors such as expected flows, water quality and rainfall predictions had experienced substantial changes, affecting the amount initially predicted to be saved and sent down the pipeline.

He also said work started on the pipeline project before the business case was done.

Mr Downie said the Foodbowl Modernisation Project - which is expected to generate 75 Gl for the pipeline, 75 Gl for irrigators and 75 Gl for the environment - was unlike other government projects.

He said government policy was made before the business case was done.

The Opposition is seeking documents sent from DSE to Melbourne Water in April 2008, which show how much water is expected to be available for the northsouth pipeline.

The government is refusing to release the documents because it says the figures were only a snapshot, have now changed, were prepared by junior staff and did not contain sufficient information for an uninformed audience to interpret them correctly.

Federal Member for Murray Sharman Stone said there was a lengthening queue of water experts who believed the pipeline was not viable.

She said now even members of the government's senior bureaucracy were saying the pipeline would not take water from savings but from the environmental reserve and savings from projects already committed to the Murray-Darling Basin environment.

State Member for Shepparton Jeanette Powell moved a notice of motion in parliament last week condemning the Brumby Labor Government.