Finding extra water by upgrading irrigation networks in northern Victoria has become the Government's preferred method of improving environmental flows and supplying Melbourne through the north-south pipeline.

Yesterday's budget papers did nothing to quell fears that water savings estimates through upgrades might be exaggerated, revealing that the Government recovered significantly less water this financial year than hoped.

Water savings already realised this financial year were forecast to be 60 billion litres lower than the target of 429 billion litres.

For upgrade projects still under way, the forecast savings for this financial year were about 50 million litres lower than the target.

The lower than expected results came during a 12-month period when spending on irrigation upgrades was higher than originally planned.

But the Government insisted yesterday that there was no problem or spending blow-out on the projects, and that minor delays had pushed back the realisation of some water savings.

"These water recovery projects are on track to deliver the same volume of water and with the same total project cost as planned," said Government spokesman Luke Enright.

But Opposition country water spokesman Peter Walsh said the extra spending and declining water savings gave credence to warnings by the Victorian Auditor-General into the food bowl and north-south pipe projects.