A Melbourne-based consortium has proposed to pipe 500 gigalitres of pure Tasmanian water to Victoria's mainland by 2011 - and it is serious.

However, the Victorian Government has hosed down the idea, stating it would be too expensive.

The project, which is still in its design phase, has been divided into two schemes. One would pipe water direct to Melbourne and fill the city's water needs for hundreds of years to come.

The other involves feeding water into the Wimmera via Warrnambool.

Project engineer Geoff Croker said the scheme would only take a small percentage of water from Tasmania's Ford River.

"There is about 5300 gigalitres which is just going out to sea - we only want 500 of that."

Mr Croker said the Wimmera scheme relied on good catchment areas. There were a "few good ones" in the south-west, he said. "An obvious one is the Rocklands Reservoir. It would allow water to flow both ways into the Glenelg or into the Wimmera."

The cost of water would be comparable with current supplies, unlike desalinated water which is more expensive, Mr Croker said.

However, Water Minister Tim Holding dismissed the project. "The proposed pipeline would cost somewhere between $8-12 billion and would include 350 kilometres under Bass Strait making construction and maintenance extremely difficult and expensive," he said. "Simply relying on our existing storages and dams - or on Tasmania's for that matter - will not secure our water future."

Mr Holding said the State Government had committed to a 150-gigalitre desalination plant and a range of regional water projects including the Hamilton-Grampians pipeline.

A spokesperson for Tasmanian Water Minister David Llewellyn said the project was not advanced enough for the Government's consideration.