“The rainfall that comes through south-east Australia, particularly through those low-pressure systems, feeds into our river systems, it feeds into the Murray-Darling Basin system,” CSIRO climate research manager Jaci Brown told TND.

“It’s an important water source for everyone through that region, for just general day-to-day life, but very importantly for our agriculture.

“Because … some agriculture is through irrigation, through the river system, but some of it is rain-fed, so we rely on those weather systems coming through, and that determines the sort of crops you can grow and how successful you’ll be year to year for those crops.”

Pressures could be made worse by potential increases of extreme wet weather during warmer months, said Kimberley Reid, research fellow at the University of Melbourne School of Geography, Earth & Atmospheric Sciences.

“We’re losing rainfall in these agriculturally significant [cooler] parts of the year, but we can still experience heavy rainfall at other times of the year,” Reid said.

“One of the big issues with climate change is that we expect our rainfall to become more more variable; to swing between periods of very dry periods to very wet.

“So we really have to be able to prepare for both sides of water extremes.”

What’s driving the change?

Low-pressure systems are responsible for at least a third of all rainfall that happens in southern Australia, and more than half of all heavy rainfall.

“To create rainfall, you really need … a lot of moisture in the air, and then something to force the air to rise so that the moisture condenses into a liquid and [rainfall],” Reid said.

“Low-pressure systems are associated with rising air, and they’re really good at forcing moist air to rise and condense and rain.

“So low-pressure systems … [are] one of the main sources of rainfall, particularly for the southern half of Australia.”

The new research suggested at least half and up to 95 per cent of the decline in cool-season rainfall between 1959 and 2023 was linked to decreases in rain from low-pressure systems and their associated cold fronts.

The article attributed declining trends in southern Australia’s cool-season rainfall to a range of factors, including human-induced climate change.

Reid said as the planet warms, low-pressure systems and cold fronts in the southern hemisphere are expected to shift further south as the tropical climate zones start to expand.

Increasing rainfall in the warmer months are also concerning.

Brown said for every degree of warming, the atmosphere can hold on to 7 per cent more moisture, which contributes to heavier rain.

“The rainfall’s dropped off, but when it does arrive, we’re seeing the heavier rainfalls get even heavier,” she said.

“When you want to take advantage of that rainfall, you don’t want it all at once, because it’ll wash away, and if the land’s dry it’s harder to soak in.”

Prevention and adaptation

Mitigation in the form of reaching net-zero emissions is crucial to stabilise the climate and stop global warming from progressing even further, but damage has already been done.

“A lot of it is locked in. These changes have already happened, and they will continue to happen, so we need to be smart about water management through those regions that are drying,” Brown said.

“Looking at how we store the water, how we use the water for agriculture, how we ration the water.”

Reid said weather forecasting should be further embedded across “all sectors of society” to improve resilience and make sure all the information available is being used to manage water resources wisely.