NATIONALS' Barnaby Joyce is claiming credit for an expected federal government announcement about flood mitigation works.

Prime Minister Julia Gillard will announce funding later today of up to $50 million a year to help pay for works such as raising the level of Sydney's Warragamba Dam by 23m.

When completed, more than 50,000 homes in western Sydney could be removed from the flood risk zone in what is now classed by insurers as one of the highest economic disaster risks in the country, The Daily Telegraph said.

The government says insurance premiums could drop by as much as a third, based on experience in areas where flood mitigation works have been completed.

Opposition water spokesman Barnaby Joyce has welcomed the expected announcement.

"I am glad we are breaking the way for the prime minister to start announcing policies that have been developed in my office," he told reporters in Canberra.

"I have got a whole range of others for her as soon as she wants to have a look at them."

The cost of raising the wall at Warragamba Dam is estimated to be $500 million, and federal funding would be contingent on state government backing for the project.

Labor backbencher Doug Cameron said there had to be a close analysis to ensure money was spent wisely and did the job.

"If you can improve water security, that's good," he told reporters.

Australian Greens leader Christine Milne welcomed the announcement but contrasted it to government decisions to cut funding for other environmental programs, such as the national climate change adaptation research facility.

Senator Milne said the announcement was related to Ms Gillard's stay in western Sydney next week.

"It's clearly in the context of the prime minister heading to western Sydney and trying to improve the government's standing," she said, adding that it followed a coalition discussion paper about more dams earlier in February.