The Climate Council has released a new report linking climate change with worsening droughts, including the current one, extreme weather events such as bushfires and floods, and identifying water security as a source of grave concern.

The report, Deluge and Drought: Australia's Water Security in a Changing Climate, stated that if the effects of climate change were left unchecked the results for the agriculture sector and beyond will be devastating.

Key points: Less water is likely to be available for agriculture, urban water supplies, and ecosystems across southern Australia

Less water is likely to be available for agriculture, urban water supplies, and ecosystems across southern Australia Less water is likely to flow into dams in southern Australia as a result of human-driven climate change

Less water is likely to flow into dams in southern Australia as a result of human-driven climate change Australia's long-term water security is dependent on action, especially the rapid phase-out of fossil fuels

According to the report, the Murray-Darling Basin — known as "Australia's food bowl" —has seen a 41 per cent reduction in "streamflows" since the mid-1990s, while water systems in Western Australia's southwest have declined by about 50 per cent.

Additionally, the report said Australia's south-east had seen a 15 per cent reduction in rainfall in late autumn and early winter, and a 25 per cent decline in rainfall in April and May over the past 20 to 30 years.

These grim figures were all related, the publicly-funded council found, to rainfall patterns thrown badly out of whack by climate change.

"Most of our [rainfall] comes from the ocean, so we are exposed to big-scale changes, and the tropics are expanding," Professor Will Steffen, one of the report's seven co-authors, said.

"That is the ultimate explanation for why these fronts in the Southern Ocean are now being pushed a bit further south, and so that means that we are getting less rainfall across the southern part of Australia.

"We're getting fewer good autumn breaks than we did before, due to the warming of the Indian Ocean."

Water security crisis could open the floodgates

According to the report, the vicious cyclic effects of climate change, driven by changes in the global water cycle, had "already had serious implications for Australia".

The authors cited the Australian Capital Territory "megafires" of 2003 (during which the world's first-known "fire tornado" was observed) as an example of the disastrous one-two punch of climate change.

A fire tornado in Thargomindah, Queensland, in 2012. ( Supplied: Sherilee Honnery )

In this instance, the regrowth of forests following the fires led to a reduction in urban water supplies in the region.

Also cited in the report was the 1997–2009 Millennium Drought, which the report stated "seriously affected Australia's agricultural sector, putting a dent in our GDP and eroding the health and wellbeing of humans and natural ecosystems alike".

"The combination of drying, extreme heat and increasingly intense bushfires has damaged or destroyed several of our most valued ecosystems, including Tasmania's World Heritage forests and alpine areas," the report said.

The report identified climate change as a "threat multiplier", with myriad knock-on effects stemming from water insecurity that extended beyond the environmental and economic all the way to social disharmony, poverty, and the prospect of future waves of "climate refugees".

Heavy toll for environment, economy

The report highlighted the impact of climate change on the environment, including freshwater fish species across Australia, the iconic sites in the Murray-Darling Basin, and World Heritage areas such as the forest and alpine areas in Tasmania, which were severely damaged by bushfires in 2016.

One of the most shocking projections in the report was a predicted 75 per cent global decline in freshwater fish, attributable to a combination of reduced streamflows and water extraction.

More locally, one of Australia's rarest species of reptile, the endangered western swamp tortoise, now numbered fewer than 200 because the swamps of south-west Western Australia were drying out.

The western swamp tortoise is threatened by changes in the water cycle. ( Image supplied Climate Centre )

Then there were the economic costs associated with climate change, including the cost of water desalination when metropolitan supplies dry up.

The report stated that water infrastructure such as dams, reservoirs and other catchments, were seeing long-term declines in inflows — and their ability to service urban areas, such as Melbourne, was in jeopardy.

It doesn't rain, it pours

The flip side to a warmer atmosphere was that it could hold more water vapour, which could lead to an increase in downpours and flash flooding.

In general, the report stated: "wet areas of the world are becoming wetter and dry areas drier as the climate continues to change".

Australian rainfall deciles for the nine months from January to September 2018 reveals extremely dry conditions in south-east Australia. ( Image supplied: Climate Council )

An average global temperature increase of 2 degrees Celsius could result in an increase in extreme rain events across Australia by 11 to 30 per cent.

Water catchments that were designed for historic rainfall patterns would have to be upgraded to cope not only with increased flooding but also harsher periods of drought.

Meanwhile, other extreme weather events such as heatwaves, floods, tropical cyclones and bushfires could reduce water quality and availability, jeopardising water security, and affecting human health.

Council urges immediate action

The report warned that "continuing on our current trajectory of high emissions has enormous and growing risks".

"Dealing decisively and effectively with climate change cannot be put off any longer," the report said.

"Solutions are available.

"We need to accelerate the transition to clean, affordable and reliable renewables and storage technologies and ramp up other climate solutions in the water, transport, agriculture and other sectors."