The Nationals leader will on Saturday announce the $100 million National Water Grid Authority, promised during this year's federal election campaign, will be established on October 1 in a bid to drought-proof Australia "when the going gets tough again".

Water storages across the eastern states have hit their lowest mark in decades in recent months, with dams feeding both Melbourne and Sydney in need of heavy spring rains to head off further restrictions on urban households.

Water authorities have warned the downward trend in storages over the past five years reflects population-driven growth in demand and less water entering reservoirs. A changing climate, with longer drier periods, higher temperatures and drier soils have reduced stream flows into reservoirs.

"We know drought is a part of Australian life. This is about security," Mr McCormack said.

He said it was "too long" since a government last built a dam, which was at Split Rock near Tamworth in 1987. The new authority would take out state-based politics and insert a national-based approach to water security, he said.

Drawing inspiration from John Bradfield's ambitious 80-year-old water infrastructure plan, which proposed using a system of hydraulic dams, pumps and pipes to divert flood water from the coastal rivers of northern Queensland inland and across the Great Dividing Range, Mr McCormack will promise a "plan for the 21st century".

"The National Water Grid Authority will open up our huge national infrastructure funding effort to deliver real results. Our generation will be seen as the one which kicked in and delivered," he said. "I intend to be known as the Nationals' leader who builds dams."

Mr McCormack said a new authority would deliver strategic planning and project management for water infrastructure, with the first major project under its remit - the 12,000 megalitre Emu Swamp dam near Stanthorpe in south-east Queensland - potentially beginning construction by the end of the year.

Mr McCormack said while it was not the federal government's responsibility to ensure urban water supply, the Emu Swamp dam "ticks all the boxes" for the new authority. The federal government has promised $42 million towards the project while local irrigators will fund $24.3 million, with an additional $18 million from the Queensland government.

The dam, subject to final project design and completion of regulatory requirements, would create 700 new full-time jobs, 135 during construction, and inject $67.8 million into the local economy.

He said work would also be under way on Central Queensland's Rookwood dam before the end of the year.

"Water is the lifeblood of our nation and we owe it to our regional producers and communities to deliver long-term, sustainable water infrastructure to help farmers recover and build resilience from drought," Mr McCormack told The Age and The Sydney Morning Herald.

He said the new authority would bring together the world's best scientists, water experts and local stakeholders to work on water infrastructure and take the "petty politics out of water".

"This will ensure that science, not politics, drives future decision-making on water policy and infrastructure," he said.

He said the authority's first task would be to look at how large-scale water diversion projects could be established, which could enable reliable and cost effective water delivery to farmers and regional communities.

"Establishing an independent statutory authority will ensure the future of Australia's water supply will be based on data, not on self-interest," Mr McCormack said.

He said the federal government would work with industry, local and state governments and communities to ensure projects were targeted to a region's needs.