Australia & New Zealand: Water deficits will persist south of Perth

Australia & New Zealand: Water deficits will persist south of Perth

22 December 2020

THE BIG PICTURE
The 12-month forecast through August 2021 indicates exceptional deficits in western Tasmania and the Derwent Estuary, and deficits of varying intensity in pockets along Australia’s southern shore from the Eyre Peninsula in South Australia through Kangaroo Island to Melbourne. Anomalies will be extreme on Kangaroo Island. At the mouth of the Murray River, however, surpluses and transitional conditions are expected. Small pockets of surplus are forecast west of Dubbo in the central Murray-Darling Basin and in the Australian Alps.

In the nation’s west, exceptional deficits are forecast along the southwestern coast from Geraldton through Perth and the Lower Blackwood River region in the tip of Western Australia to Albany. Surpluses are forecast from the Upper Blackwood River region into the southern Avon River Basin. Widespread, exceptional surpluses are expected spanning the western edge of the Gibson Desert.

Relatively mild surpluses are forecast across the northern reaches of Australia with moderate anomalies along Eighty Mile Beach in the west and the Gregory Range in northern Queensland. Intense deficits are expected in northeast Queensland near Cairns and at the northeast corner of the Simpson Desert in the Outback. A few pockets of moderate deficit are expected near Bundaberg and the Upper Weir River along the east coast.

In New Zealand, deficits are forecast along the east coast between Christchurch and Dunedin. Surpluses and transitional conditions are forecast in New Caledonia.

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

The forecast through February 2021 indicates that much of Australia will return to near-normal conditions as deficits retreat. Intense deficits will persist along the nation’s southwestern coast from north of Perth through Busselton to Albany. Surpluses are expected nearby in the southern portion of the Avon River Basin. Exceptional surpluses will re-emerge spanning the western edge of the Gibson Desert in Western Australia. Mild to moderate surpluses will emerge across Australia’s northern reaches.

In southeastern Australia, pockets of surplus will persist in the Murray-Darling Basin west of Dubbo, in Riverina, around Canberra, and at the mouth of the Murray, where exceptional anomalies are forecast along with transitional conditions. Some deficits will persist on the southern coast west of Melbourne. Deficits in Tasmania will downgrade.

In New Zealand, surpluses will nearly disappear and deficits will shrink and downgrade, persisting from Christchurch to Dunedin. New Caledonia will transition from intense deficit to near-normal conditions.

From March through May 2021, surpluses will nearly disappear in the Murray-Darling Basin, persisting with intensity near the mouth of the Murray. Intense surpluses will also persist in Western Australia southwest of the Gibson Desert and the southern Avon River Basin. Australia’s northern reaches will normalize, with a few lingering pockets of surplus. Deficits will shrink in Australia’s southwestern tip and in coastal Victoria. Conditions in Tasmania and New Zealand are expected to be near-normal. Surpluses are forecast for New Caledonia.

The forecast for the final months – June through August 2021 – indicates nearly normal conditions overall with surpluses at the mouth of the Murray River, south of Canberra, and a few pockets in the west. Intense deficits will emerge around Lakes Gordon and Pedder in Tasmania.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
A late-November heatwave hit Australia, putting firefighters on alert and prompting fire bans in parts of South Australia, New South Wales, and Victoria. Temperatures were in the 40s C (+100F) in many regions, and reached 46C (114.8F) in Coober Pemby, South Australia.

In an historic decision, Australia’s southeastern state of Victoria has returned water rights to Indigenous owners. The use of two billion liters of water will now be governed by the Gunaikurnai Land and Waters Aboriginal Corporation whose members have traditionally occupied Gippsland in the southern region of Victoria.

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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Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.25°x0.25° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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