Australia & New Zealand: Water surplus will increase in E & N Australia

24 October 2022

THE BIG PICTURE
The 12-month forecast through June 2023 indicates moderate to severe water surpluses in eastern New South Wales, Australia, from the Central West region surrounding Dubbo to the coast including Sydney.

In Queensland, generally moderate surpluses are forecast in a few pockets west of Brisbane and in the Atherton Tablelands in North Queensland, but surpluses will be more widespread and intense north of the Holroyd River in the Cape York Peninsula.

Also in the north, surpluses are forecast in Top End, Northern Territory and the nearby the Tiwi Islands. In Western Australia, surpluses are expected along Eighty Mile Beach in the northwest while in the south surpluses will be intense in the Upper Avon River Catchment, but intense deficits are predicted in coastal regions nearby from Perth to Albany.

Deficits will be widespread and exceptional in western and southern Tasmania, and pockets of deficit are forecast in the coastal mainland in Cape Otway, Victoria, and from the Eyre Peninsula in South Australia through Kangaroo Island and the Limestone Coast.

In New Zealand’s South Island, surpluses are forecast near the city of Christchurch and pockets at the northern end of the island, but moderate deficits are expected in Southland Region, becoming severe in Fiordland. On North Island, surpluses are forecast near Wellington, in coastal areas of the east, and from Auckland to the north. New Caledonia will also see surpluses.

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

The forecast through December indicates that surpluses will increase in eastern Australia and emerge in the nation’s far north. Surpluses are forecast from Wide Bay-Burnett in Queensland (QLD) through eastern New South Wales (NSW) to Canberra, picking up again in eastern Victoria (VIC). Anomalies will be especially widespread in NSW, extreme in pockets north and east of Dubbo, and will reach inland to the confluence of the Macquarie and Barwon Rivers. Moderate surpluses are forecast on the Darling and Murray Rivers. In QLD, surpluses are forecast on the Upper Mackenzie River, in a coastal pocket of the Mackay Region, and in the Cape York Peninsula where anomalies will be severe to extreme. Surpluses will be severe in Top End, Northern Territory (NT), and will skirt the Kimberley Coast in Western Australia (WA). In southwestern WA, deficits will persist from Perth to Albany, more intense in the south. Nearby, intense surpluses will persist in the Avon River region. In VIC, intense deficits will persist in Cape Otway, and surpluses will increase in Gippsland and emerge around Bendigo in the state’s center. Deficits in Tasmania will downgrade though remain exceptional in Hobart and on the Derwent River. In New Zealand, moderate deficits will emerge in southern South Island and moderate surpluses will linger in North Island and a few points on South Island.

From January through March 2023, surpluses will shrink and downgrade in eastern Australia but remain widespread in NSW between the Macquarie and Macintyre Rivers. Surpluses will also persist near Canberra, in Gippsland and Bendigo, and in pockets west of Brisbane. Surpluses will shrink and moderate in Top End and persist in the Cape York Peninsula’s north. In WA, surpluses will emerge in Eighty Mile Beach and persist in the Avon River Catchment, while deficits persist on the southwestern coast. Conditions will begin to normalize in Tasmania and will return to normal in New Zealand. Moderate surpluses will emerge throughout New Caledonia.

The forecast for the final months – April through June 2023 – indicates near-normal conditions overall with surpluses in New Caledonia and lingering pockets in Australia.

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

IMPACTS
Heavy rainfall continued in eastern Australia in October leaving 11,000 displaced Victorians. Ground already saturated from the wettest August in over a decade simply couldn’t absorb September’s delivery of above average precipitation to much of northern Victoria. In Mooroopna, 6,000 properties were without power and 355 roads closed. In the town of Echuca, the water level of the Murray River has reached 94.7 meters, a level last seen in the flood of October 1993, and is approaching the 1916 level of 95.8 meters.

Across the state, over 120 schools and 100 early learning center closed with students being relocated to other districts. A former quarantine facility in Mickleham has been repurposed as a shelter for 250 people, and 100 defense personnel were deployed to help with evacuations and sandbagging.

In New South Wales, the number of local government areas with official natural disaster declarations due to flooding since mid-September has risen to 43. The declaration will release funding for flood repairs.

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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