Moves to prevent water theft come as the Greens Party confirmed it would lobby the non-Government parties in the Victorian Parliament's upper house to block Government attempts to formalise the pipe's water entitlement.

The Age revealed last week that Country Fire Authority crews would be able to source water from the pipe when battling blazes north of Melbourne.

But with water theft an increasing problem in drought-stricken rural Australia, pipe project director Rod Clifford confirmed that each hydrant would require security measures to protect supplies.

"The off-takes themselves will be placed in locked cabinets, with only the CFA and Melbourne Water holding the keys," he said.

"There will be a flow meter installed on the off-take point to allow Melbourne Water to report the amount of water drawn down against its allotment of water each year."

Taking water for firefighting could reduce the amount that reaches Melbourne's Sugarloaf reservoir, with Mr Clifford saying there were no plans to limit the amount of water that could be taken by fire crews.

The 70-kilometre pipe will run through fire-sensitive parts of the State, with the town of Yea particularly threatened by fire in recent years.

Mr Clifford confirmed that pipe works were likely to occur within forests during times of total fire bans.

Despite work starting on the pipe, Greens MP Greg Barber believes the non-Government majority in the Victorian Legislative Council could yet prevent the Brumby Government from awarding a water entitlement to pipe owners Melbourne Water.