Australia & New Zealand: Water surplus forecast from Brisbane through the Alps

21 November 2020

THE BIG PICTURE
The 12-month forecast through July 2021 indicates exceptional deficits in western Tasmania 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 exceptional on Kangaroo Island. At the mouth of the Murray River, however, surpluses and transitional conditions are expected. Pockets of surplus are forecast west of Dubbo in the central Murray-Darling Basin and near the southeast coast in Canberra and the Australian Alps.

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In the nation’s west, exceptional deficits are forecast along the southwestern shore 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 along with some transitional conditions. Northwest of the Gibson, moderate surpluses are forecast in the Hamersley Range and along Eighty Mile Beach. Some surpluses will pock Australia’s far northern coastline. Severe deficits are expected in northeast Queensland near Cairns.

In New Zealand, surpluses are expected north of Auckland and on the points framing the Bay of Plenty. Deficits are forecast from northeast of Wellington to Hawke’s Bay. On South Island, some deficits are expected 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 January 2021 indicates that much of Australia will return to near-normal conditions as deficits retreat. Deficits will persist along the nation’s southwestern coast, of moderate intensity near Perth but exceptional to the south near Busselton. 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 with less intense anomalies and transitional conditions creating paths leading both north and south.

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In southeastern Australia, moderate surpluses will increase in a wide path along the coast from south of Brisbane through Sydney, Canberra, and the Australian Alps. Surpluses will persist west of Dubbo in the central Murray-Darling Basin and will increase in the Riverina area. At the mouth of the Murray, intense surpluses and transitional conditions are forecast. Deficits, primarily moderate, are forecast along the southern coast west of Melbourne and in southern and western Tasmania. In Australia’s northern reaches, some pockets of moderate surplus are forecast in Top End and the Cape York Peninsula.

In New Zealand, anomalies will shrink considerably, leaving deficits along the eastern coasts from Hawke’s Bay in the north to Dunedin in the south. Conditions in New Caledonia will become nearly normal.

From February through April 2021, surpluses in southeastern Australia will shrink considerably, leaving moderate surpluses south of Canberra and in southern Riverina. Deficits will intensify in a small pocket of the mainland coast spanning the border of South Australia and Victoria but will nearly disappear in Tasmania. Transitional conditions are expected near the mouth of the Murray. In Western Australia, deficits in the southwestern tip will shrink but remain intense, and surpluses will persist in the southern portion of the Avon River Basin. Surpluses near the Gibson Desert will shrink, and moderate surpluses will emerge to the northwest in the Hamersley Range and Eighty Mile Beach.

Nearly normal conditions are expected in New Zealand with some surpluses in the north and mild deficits in the south. Severe surpluses are forecast in New Caledonia.

The forecast for the final months – May through July 2021 – indicates nearly normal conditions for much of the region with surpluses at the mouth of the Murray River and a few persistent pockets in Western Australia. Intense deficits will emerge around Lakes Gordon and Pedder in Tasmania. Surpluses are forecast in New Caledonia and far northern New Zealand.

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

IMPACTS
The Australian Bureau of Meteorology reports that rainfall in the southwest of Western Australia remains below average and root-zone soil moisture has decreased.

Water restrictions for businesses in Auckland, New Zealand were relaxed in October but continued for outdoor residential use. The region’s AU $224 million (USD $163.6 million) response to the drought includes bringing two bores in Pukekohe, dormant since 2013, back online.

Though Australia’s “Milennium Drought” from 2001-2009, decimated fish populations in the River Murray, experts say aquatic life is finally making a come-back after a decade of recovery. Aided by long-term environmental engineering, sufficient rainfall, and fish ladders, many native migratory fish, like the congolli and pouched lamprey are once again flourishing.

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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