The federal coalition has no specific plan yet to build 100 dams across Australia.

But the idea does show a long-term vision for alternative government, its environment spokesman Greg Hunt says.

Opposition Leader Tony Abbott reportedly is considering building up to 100 dams across the country as part of a plan to prevent floods, fuel power stations and irrigate food bowls.

The idea, outlined in a leaked draft policy discussion paper, would cost around $30 billion if the projects were approved and implemented.

It includes a $500 million plan to raise Warragamba Dam in Sydney and flags new dams for the Hunter Valley and along the Lachlan River, News Limited reports.

Most however would be constructed in northern Australia, and would be used to irrigate dry zones and more than double Australia's food production.

Mr Hunt says the coalition has no direct proposal for the dams, but forward thinking is necessary for anyone wanting to run government.

"You can't just make it up as you go along," he told ABC Radio on Thursday.

The coalition was "unashamed" about having plans to tackle floods and build Australia into one of the world's great food bowls.

"What we have set out is a vision for northern Australia, and linked to that is a vision for new dams," he said.

"We are proud of establishing a vision, but these are draft papers."

A coalition taskforce will update its ideas and formally release them as the year progresses, he said.