THE Federal Government has broken a promise to buy $22 million of water from seven irrigation families at Moulamein as part of its $3.1 billion environmental water-purchasing program.

On July 8, a Federal Government water purchasing manager emailed the families stating: "I can confirm that the following offers have been assessed and the Department (of Environment, Water, Heritage and the Arts) has decided to pursue them subject to due diligence".

Yet the families' solicitor Nicholas Rolf said he then received a call from the same manager on August 28 stating "he had made a mistake".

The backflip has been devastating for the families involved who, like other Murray Irrigation Limited irrigators, are entering their fourth season without water.

Moulamein irrigator Ian Shippen said the Government's rejection of the families' offers of $1100 a megalitre was bitterly disappointing.

The Department of Environment, Water, Heritage and the Arts website shows it paid $1200-$1300 a megalitre for NSW general security water on the Murray as part of its second-round tender.

Mr Rolf said the group was even more frustrated that Water Minister Penny Wong's department still claimed it was processing all offers it accepted as part of the tender.

The seven families who tried to sell their water to the Government were originally part of a group of 12, which offered a parcel of 40,000 megalitres.

Group member Jeremy Morton said the 12 families had offered to stop irrigating, which would have allowed Murray Irrigation Limited to close down their 50km delivery channel, creating several more thousand megalitres of water savings.

But Mr Morton said MIL had procrastinated for months on determining how much water could be saved and how it would be valued.

"We're not willing to go just for the price of water," Mr Morton said.

"If you take water off our land (and close down the channel) it takes two-thirds of the value off the property."

The Federal Government failed to respond to a request for comment.