Living Land

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Australia prepares for a

cycle of extreme droughts

Professor Craig Simmons, Director, National Centre for Groundwater Research and Training, Australia

limate change projections do not augur well for

Australia, with forecasts of more severe droughts

for a sun-baked nation where water is already a

precious commodity.

The oldest continental landmass on Earth is also the driest

after Antarctica. It is characterized by a cycle of droughts

which parch the heavily weathered landscape eroded over

millions of years. About a third of the continent has so little

rain that it is effectively desert. Just over two-thirds of main-

land Australia receives less than 500 millimetres of rain a

year and is classified as arid or semi-arid. As the planet

warms, weather records across Australia are tumbling, with

hotter, drier conditions over much of central and southern

Australia. Climate scientists are worried that even less rain

will fall in future in the areas where it is needed most.

The so-called millennium drought which gripped

south-west Western Australia, south-east South Australia,

Victoria and northern Tasmania was described by the

Bureau of Meteorology (BoM) as without historical prec-

edent. Temperatures were about 1 degree Celsius hotter

than previously recorded droughts and the duration —

from 1995 until 2012 in some areas — was the longest

ever known.

Drought in Australia coincides with the cyclical weather

pattern El Niño when a band of warm ocean water rises off

the coast of South America and expands westward across

the Pacific Ocean to displace colder waters. This is associ-

ated with decreased rainfall for Australia, very hot daytime

temperatures and earlier, more extreme fire seasons.

Nine of the ten driest winter-spring periods on record for

eastern Australia have occurred during El Niño years. In the

Murray-Darling basin — the so-called food bowl of Australia

— winter-spring rainfall during El Niño events since 1900

averaged 28 per cent lower than the long-term average.

The opposite phase of El Niño is La Niña when Australia

faces a higher risk of flooding, lower temperatures and

more tropical cyclones. Successive La Niña events during

2010-12 were associated with record rainfall over much of

Australia and some of the biggest floods in living memory.

As climate change takes hold, more extreme versions of

the El Niño Southern Oscillation cyclical weather pattern are

expected to result in more frequent flooding and drought.

Modelling of weather data by scientists at BoM and the

national science agency CSIRO shows that under projected

global warming scenarios Australia can expect ‘super’ El

Niños that are more intense, and that they are likely to occur

twice as often.

Their fears are already being realized. Just three years

after the official end of the millennium drought in 2012,

BoM declared a major new El Niño event. By mid-2015

Queensland was in the grip of an unprecedented drought

covering a record 80 per cent of the state. Rainfall was

also lower across large tracts of southern Australia

and western Tasmania.

Such extreme weather behaviour is in line with the latest

dire predictions from the United Nations Intergovernmental

Panel on Climate Change (IPCC). In its 2014 report, IPCC

said Australia could expect more frequent flooding in some

areas and severe drying in the Murray-Darling basin and in

south-western and south-eastern Australia. These are key

agricultural regions in arid and semi-arid areas and, if the

worst-case scenario is realized, production could fall by a

disturbing 40 per cent.

Image: istock.com/BenGoode

Various initiatives have been instigated to gauge Australia’s current and

future water use and inform sustainable planning and management

iving

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