Australia & New Zealand: Water surpluses will persist in E Australia

21 January 2022

THE BIG PICTURE
The 12-month forecast through September indicates widespread water surpluses in Australia’s east. Anomalies will be extreme south of Rockhampton, Queensland, and moderate to severe in New South Wales and Victoria with surpluses expected from the eastern Murray-Darling Basin to the coast.

Moderate deficits are expected along the nation’s south coast west of Melbourne, becoming more intense across the border into South Australia including Kangaroo Island and the southern tip of the Yorke Peninsula.

Extreme to exceptional deficits will dominate western Tasmania, the Derwent Estuary, and Hobart.

In Western Australia, extreme to exceptional water surpluses are forecast in the Avon River catchment leading south. Severe deficits are expected along the west coast south of Geraldton. Pockets of surplus will form a broken path from the Great Victoria Desert’s western edge tracking south. In the north, some small areas of moderate deficit are forecast at the northern edge of the Kimberley Plateau and around Darwin in Northern Territory, but moderate surpluses are forecast in Arnhem Land. On Queensland’s northern coast a pocket of intense deficit is expected south of Cairns.

Overall, normal water conditions are expected in New Zealand with some surpluses north of Auckland and in East Cape, North Island, and some deficits in the Catlins Coast of South Island. Mixed conditions are forecast in New Caledonia.

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

The forecast through March indicates that surpluses in eastern Australia will shrink slightly and downgrade, returning normal conditions to the Darling River’s path, but will remain widespread. Anomalies will be severe to exceptional south of Rockhampton and in Murweh Shire, South West Queensland, and moderate to severe between the Macintyre and Macquarie Rivers in New South Wales and from Sydney into Victoria. Moderate surpluses are expected in the Grampians of Victoria and intense surpluses in the Lower Murray region of South Australia. Deficits will increase slightly along the coast near Melbourne and into South Australia. In Tasmania, deficits will increase in the island’s western half as surpluses in the east shrink. Western Australia will continue to see intense surpluses in the Avon River catchment and deficits along the coast around Busselton and south of the Blackwood River. In Northern Territory, some moderate surpluses will linger in Arnhem Land.

A few pockets of moderate deficit are expected in South Island, New Zealand, and surpluses along North Island’s east coast. Deficits in New Caledonia will shrink.

From April through June, surpluses in eastern Australia will continue to shrink and moderate overall though anomalies will be severe south of Rockhampton. In the west, surpluses will also shrink in the Avon River catchment but will include intense anomalies. Deficits will nearly disappear from Victoria’s coast and from the nation’s southwestern tip and will downgrade in Tasmania. Anomalies will shrink in New Zealand, leaving surpluses in East Cape, North Island, and moderate deficits on South Island’s southern shore. Deficits will disappear in New Caledonia as mild surpluses emerge.

The forecast for the final months – July through September – indicates that surpluses will increase in the eastern Murray-Darling Basin, decrease south of Rockhampton and in the Avon River catchment in the west. Intense deficits will emerge in the Kimberley Plateau and Northern Territory, deficits will intensify in pockets of western Tasmania, and will increase somewhat in South Island, New Zealand.

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

IMPACTS
The remnants of Tropical Storm Seth produced flooding in eastern Queensland, Australia in early January prompting evacuations on the Mary River. A flood levy erected to protect commercial properties in Maryborough failed, leaving a hundred businesses inundated. The Fraser Coast and Gympie regions reported significant rainfall and flooding as well, with 674 mm (26.5 inches) falling in just 24 hours. Over 30 swift-water rescues were performed and at least one death reported.

Thunderstorms in the Riverina region of New South Wales caused flooding on roadways and forced closure of the Griffith Airport as debris floated over the runway and into the terminal.

Later in the month, the Darling River overflowed in the NSW towns of Wilcannia, Tilpa, Bourke and Menindee Lakes.

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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