MELBOURNE will be denied access to more than 30,000 megalitres of water the State Government expects to save from the $1 billion Northern Victorian Irrigation Renewal Project this season.

Goulburn Murray Water expects to deliver the water savings by the end of this season on top of about 8000-10,000 megalitres saved from the project in 2008-09.

However, the Opposition has already put Water Minister Tim Holding on notice that it intends to block crucial government amendments to the Eildon-Goulburn bulk entitlement, which allow Melbourne to divert NVIRP water savings down the north-south pipeline to Sugarloaf Reservoir.

The Opposition notified Parliament last Friday that it intends to put a motion to the Upper House in February or March disallowing the government amendments to the bulk entitlement.

But the Government will still be able to divert about 22,000 megalitres of water down the pipeline next February that were not created from the project.

As The Weekly Times first revealed in September, the Government is taking 12,000 megalitres traditionally supplied from the Goulburn irrigation system to Wimmera Mallee farmers and towns, plus another 10,000 megalitres from Eildon's water quality reserve to supply Melbourne.

Opposition rural water spokesman Peter Walsh said the motion to disallow the bulk entitlement amendments would most likely be debated after the Victorian Auditor General's report into NVIRP was tabled in Parliament early in the New Year.

"Labor has grossly overestimated the water savings available through the modernisation project and it is now in a panic to raid water previously committed to the environment," Mr Walsh said.

Federal Water Minister Penny Wong has threatened to withdraw $1 billion of federal funding for stage two of the project if the Upper House disallows the bulk entitlement amendments.

The Government issued another round of amendments to the bulk entitlement this month, which grant Melbourne's South East Water, Yarra Valley Water and City West Water bulk entitlements in the Goulburn and Murray River systems.

A notification of the amendments published in today's Weekly Times states Water Minister Tim Holding has written to GMW confirming a share of the water savings be distributed to irrigators.