Australia & New Zealand: Water deficits to persist in Victoria & Tasmania

19 February 2020

THE BIG PICTURE
The 12-month forecast through October indicates a wide path of water deficits along Australia’s east coast from Cairns in northern Queensland through the eastern Murray-Darling Watershed and Tasmania. Deficits will range in intensity and anomalies will be exceptional in many pockets.

In South Australia, exceptional deficits are forecast from Adelaide to the border with Victoria, including Kangaroo Island.

ISciences_Australia_New_Zealand_Composite_Adjusted_201911-202010_12mo_panel.png

Severe to exceptional deficits are expected in Top End, Northern Territory and to the west along the coast of northern Kimberley, Western Australia. The McDonnell Ranges in the center of the country west of Alice Springs can expect exceptional deficits. Moderate to severe deficits are forecast in Western Australia around Perth, leading south to exceptional deficits in the Busselton and Blackwood River region in the nation’s southwestern tip.

A large pocket of exceptional surplus is forecast crossing the western Gibson Desert in Western Australia connecting to surpluses of lesser intensity along the De Grey and Fortescue Rivers to the north and a few pockets trailing south. A small pocket of intense surplus is forecast inland of the southern coast of Western Australia north of Esperance.

In New Zealand, moderate to extreme deficits are forecast from the center of South Island to the northern tip of North Island. Surpluses are expected in the southwestern and northeastern tips of the country. Severe to extreme deficits are forecast for New Caledonia.

FORECAST BREAKDOWN
The 3-month maps (below) show the evolving conditions in greater detail.

The forecast through April indicates that deficits will shrink and downgrade considerably in Australia leaving just a few relatively small pockets of exceptional deficit in stark contrast to widespread intense deficits observed in the prior three months. Areas of intense deficit include the Blackwood River region in the southwestern tip of Western Australia (WA) and the confluence of the Murray and Darling Rivers in New South Wales (NSW). Primarily moderate to severe deficits are expected from Canberra to Melbourne in the southeast but deficits will be more intense in Tasmania (TAS) with exceptional anomalies in Hobart and along the Derwent River.

ISciences_Australia_New_Zealand_Composite_Adjusted_201911-202010_3mo_panel.png

A large pocket of exceptional surplus is forecast crossing the western Gibson Desert in WA connecting to surpluses of lesser intensity along the De Grey and Fortescue Rivers to the north and a few pockets trailing south. A small pocket of intense surplus is forecast inland of WA’s southern coast north of Esperance. A broad belt of moderate surplus will emerge south of Top End, Northern Territory (NT).

In New Zealand, moderate surpluses will persist in Fiordland in South Island. Deficits of varying intensity are forecast for much of remainder of the island as well as much of North Island. Deficits will downgrade from exceptional in New Caledonia but will remain intense.

From May through July water conditions will become nearly normal in much of Australia. Exceptional surpluses will persist in the western Gibson Desert in WA and surpluses of lesser intensity along the De Grey and Fortescue Rivers, with conditions of both deficit and surplus (pink/purple) in the middle reaches of the Fortescue. A pocket of exceptional surplus will also persist in southern WA north of Esperance. Surpluses south of Top End, NT will nearly disappear. Severe deficits are forecast down the center of TAS, and moderate to severe deficits in the western region of North Island, New Zealand.

The forecast for the final months – August through October – indicates the emergence of exceptional deficits in Arnhem Land, NT and along the coast of northern Kimberley. Moderate surpluses will emerge in NSW in the northeastern reaches of the Murray-Darling Basin, and will re-emerge south of Top End, NT. Intense surpluses will persist in WA in the western Gibson Desert, along the De Grey and Fortescue Rivers, and north of Esperance.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
Torrential rainfall, Sydney’s worst in 30 years, has succeeded in quenching several massive bushfires in New South Wales while bringing yet another threat to fire-ravaged areas as flooding ensues. Though the downpours helped extinguish the Currowan Fire after it had burned for 74 days and destroyed 500,000 hectares (1.2 million acres), thousands of people were ordered to evacuate when the Hawkesbury River breached its banks northwest of Sydney and the Georges River threatened properties to the southwest. The Wattamolla region received 266 mm (nearly 10.5 inches) of rainfall from the morning of 9 February to afternoon. At least 137,000 people were without power due to high winds that accompanied the storm.

Water levels at area dams were swelling rapidly, with Warragamba Dam receiving 40 billion litres of water daily and forecasts targeting 55 percent capacity, an increase representing the recovery of nine months of supply in less than a week.

Insurance claims for the devastating fires in Australia that began in September currently total $700 million (~USD $500 million) with those numbers expected to rise. The federal government announced an emergency aid package of $2 billion (~USD $1.4 billion) with one expert estimating the nation’s eventual costs from the disaster will reach $100 billion (USD $70 billion.

One lesser known consequence of the fires is the decimation of the bee population. In New South Wales 6,000 hives were lost to fire and smoke and 2,000 hives in South Australia. Honey bee pollination contributes $6 billion (USD $4 billion) annually to the national economy and the lack of viable pollinators could affect the nation’s almond industry.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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