Australia & New Zealand: Pockets of surplus in the Murray-Darling

27 January 2021

THE BIG PICTURE
The 12-month forecast through September 2021 indicates severe deficits in western Tasmania, Australia and near Hobart, and deficits of extreme intensity in the Derwent Estuary. Some moderate deficits are expected in mainland Australia in pockets along the southern coast from Melbourne past Adelaide, with severe deficits in western Kangaroo Island. At the mouth of the Murray River in South Australia, however, surpluses and transitional conditions are expected.

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Pockets of surplus are forecast west of Dubbo in the central Murray-Darling Basin of southeastern Australia, in the Australian Alps, and along the nation’s southeastern coast, particularly near Armidale. Some areas of moderate deficit are expected in coastal Queensland near Brisbane and on the Burnett River. In northern Queensland, moderate surpluses are forecast west of Townsville and in some pockets of Cape York Peninsula, but intense deficits are expected along the coast near Cairns. Elsewhere in Australia’s north, moderate surpluses are forecast south of the Kimberley Plateau in the west and pockets in Northern Territory’s Daly Waters area.

In the nation’s west, exceptional deficits are forecast along the southwestern coast between Geraldton and Perth, moderating near Perth, becoming exceptional again in Busselton and the Blackwood River region, then downgrading along a small stretch of the southern coast towards Albany. Intense surpluses are forecast in the southern Avon River Basin, a pocket north of Esperance, and a large pocket spanning the western edge of the Gibson Desert. Surpluses of lesser intensity are expected in a path north of the Gibson Desert, a path through the western region of the Great Victoria Desert, and a pocket in the Simpson Desert in the center of the nation.

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 March 2021 indicates that deficits will retreat, persisting in southwestern Australia from south of Perth to Albany. Surpluses will persist in the Avon River Basin and a pocket north of Esperance. Intense surpluses will re-emerge at the western edge of the Gibson Desert. In the north, surpluses will shrink and moderate south of the Kimberley and in Top End. In northern Queensland, intense deficits near Cairns will retreat. Surpluses will emerge in the Burdekin River Basin and in Cape York. In New South Wales, moderate surpluses will increase around Armidale, but will shrink somewhat in the Murray-Darling Basin. Surpluses and transitional conditions will persist near the mouth of the Murray, and deficits will persist on the southern coast through Melbourne. Anomalies in Tasmania will shrink considerably. Nearly normal conditions are forecast for New Zealand with some deficits persisting from Christchurch to Dunedin and a few areas of North Island. New Caledonia will be in transition from intense deficit to surplus.

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From April through June 2021, surpluses will nearly disappear from southeastern Australia, persisting near the mouth of the Murray. Surpluses will shrink slightly but persist in Western Australia southwest of the Gibson Desert and in the southern Avon River Basin. Australia’s northern reaches will normalize, with a few lingering pockets of surplus. Areas of prior deficit in Australia’s southwestern tip and coastal Victoria will become nearly normal as will conditions in Tasmania and New Zealand. Surpluses in New Caledonia will diminish.

The forecast for the final months – July through September 2021 – indicates that surpluses will persist at the mouth of the Murray River, southwest of the Gibson Desert and a few other pockets in the west, and in coastal Queensland near Cairns. Surpluses will emerge in the eastern Murray-Darling Basin, and pockets along the southeastern coast. Moderate deficits will emerge in southern Tasmania. Near-normal conditions are expected in New Zealand and New Caledonia.

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

IMPACTS
Hot, dry conditions in early January helped fuel a bushfire north of Perth in Western Australia that threatened hundreds of residents, prompting evacuation orders. The fire raced over at least 35 square miles, destroyed 75 acres of olive trees, and approached the site of an old bombing range containing unexploded ordinance. Two hundred fire fighters were deployed, aided by aerial support that included two air tankers from Victoria.

North Queensland caught the edge of ex-Tropical Cyclone Imogen in the first week of the year with over 185 mm (7.3 inches) of rainfall reported during just two hours in the town of Ingham where cars floated in the streets. Flood warnings were issued for many riverside communities and numerous roads were impassable. Emergency service personnel fielded over 100 calls for help. A major highway near Townsville was closed for three days as waters of the Burdekin River reached the base of the Macrossan Bridge. The Thomson River near Longreach breached its banks. Disaster recovery funding was announced through a joint federal-state arrangement.

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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