Australia faces a "perilous" water security future from climate change even as the Turnbull government eyes budget cuts to water programs and CSIRO halves climate investment, the outgoing head of the Bureau of Meteorology has warned. 
Reservoirs in the Murray-Darling basin are now close to their lowest levels since the Millennium drought and Tasmania is also facing "serious" issues", Rob Vertessy said on Friday, his final day as the bureau's chief.
"Water shortage is a problem and climate change is going to be intensifying the drought and flood cycle," he said, noting that water demand is increasing. "Australia faces a really perilous water security challenge in the future."
Dr Vertessy bowed out just days before the federal budget on Tuesday will reveal whether the government axes funding for programs set up under the National Plan for Water Security. Begun in 2007 by then prime minister John Howard, the 10-year, $10 billion program funded a range of water policies, with almost $450 million going to the bureau.
The bureau now had "the world's best water information service", including precise stream-flow forecasting, that boasts a return on investments of between twofold and ninefold, despite the early stage of many projects, Dr Vertessy said. A drop in funding would result in a sharp reduction of services.
Funding constraints also hindered the bureau's ability to win its case to house climate researchers facing the chop at the CSIRO.
Facing criticism at home and abroad, CSIRO last week announced that it would instead form a special climate science centre of 40 staff under its Oceans and Atmosphere division. About 45 of the remaining 100 scientists in two key programs will lose their jobs and the future of those remaining is uncertain.
Dr Vertessy welcomed the centre's creation as an advance: "We were looking at the complete elimination of [the climate program] at one stage," he said "Let's not sugar-coat it - CSIRO are diminishing their investments overall, they are probably halving them. So it's really up to the rest of us now to work with them to build up the national capability to what it should be."
The need to boost global warming research was only going to increase, he said. In Australia's case, the threats included lengthening and intensifying fire seasons, worse heatwaves and more intense storms.
"Unless we start slowing down our [greenhouse gas] emissions and really mitigating them completely in the next few decades, there's going to be a lot of environmental shocks to the planet," Dr Vertessy said.
The outgoing boss added he "never felt hobbled" despite attacks on the bureau from some members of the Coalition, particularly during the Abbott era, and from climate change deniers who claimed the agency revised temperature data higher.