The Murray Darling Basin agreement between the States and the Federal Government could be on the rocks again following attempts to try and block the Sugarloaf pipeline to Melbourne before a national takeover of water can finally happen.

The Water Amendment Bill, which puts into effect Labor's $12.9 billion buyback and infrastructure policies, has dominated the Senate this week but hit a snag when Opposition and minor parties successfully passed changes to the Bill to block the pipeline's construction.

The Bill will now head back to the House of Representatives with a suite of major changes, but will most likely be counter-blocked by the Labor Government.

This would then see the Bill plunge into limbo.

Late last night, Liberals, Nationals, Greens and Independents Steve Fielding and Nick Xenophon combined to change the Bill so that it prevents the taking of new water from the Murray Darling Basin, with hours of the debate dedicated to the Victorian pipeline.

Other major amendments will see an inclusion of a definition of the term "critical human needs" which spell out the requirements for providing drinking, health and sanitation water in urban areas from the Murray Darling, and what that water can specifically be used for.

There was also a successful amendment designed to start weaning major cities off the Murray Darling Basin over time.

Whether Labor in the Lower House agree to the amendments in order to see the Bill finalised before Christmas will be the next hurdle next week - the last sitting week for year.

* More details in this week's Fairfax weekly rural newspapers, including The Land, NSW, Stock & Land, Vic, Stock Journal, SA, and Queensland Country Life.