Australia & New Zealand: Water surplus forecast in coastal SE Australia

24 March 2021

THE BIG PICTURE
The 12-month forecast through November 2021 indicates moderate to exceptional deficits in Queensland along the coast north of Townsville and farther south near Rockhampton, downgrading somewhat as they reach inland into the Buckland Tableland.

Also in the east, surpluses are expected in some pockets of Cape York Peninsula in the north, along the nation’s southeast coast near Armidale in New South Wales, in the Upper Murray River region of Victoria, and approaching the mouth of the river in South Australia where anomalies will be exceptional. In Tasmania, however, deficits are forecast in the south, moderate near Hobart and in the Derwent Estuary but severe south of Lakes Pedder and Gordon.

Australia_New_Zealand_Composite_Adjusted_202012-202111_12mo_twitter.png

In Australia’s western half, deficits will be intense in the Great Sandy Desert and a pocket along the northwestern coast in the Kimberley region. Surpluses are forecast in the southern Avon River Basin east of Perth; a pocket north of Esperance; between the Gibson and Great Victoria Deserts; the Victoria River region of Northern Territory; scattered pockets in South Australia; and a pocket in the Simpson Desert in the center of the nation.

In New Zealand, scattered deficits are forecast, primarily moderate but severe near South Island’s three glacial lakes, Pukaki, Tekapo, and Ōhau. Surpluses are expected in eastern New Caledonia.

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

The forecast through May indicates that deficits will shrink and downgrade, persisting near Rockhampton in coastal Queensland and in the Buckland Tableland nearby; west of Melbourne; and between Perth and Busselton. Surpluses will shrink across the northern reaches of the nation and in the southeast, with moderate anomalies in the Victoria River region of Northern Territory, on the southeast coast near Armidale, and in Victoria’s Australian Alps in the east and Yarriambiack Shire in the west. Intense surpluses and transitional conditions will persist in the Lower Murray River in South Australia.

Australia_New_Zealand_Composite_Adjusted_202012-202111_3mo_twitter.png

In the nation’s west, surpluses reaching exceptional intensity will persist in the Avon River Basin and will re-emerge at the western edge of the Gibson Desert. Some pockets of moderate surplus will re-emerge in the Great Victorian Desert and in South Australia.

In New Zealand, scattered deficits are forecast. Moderate surpluses are expected in southern New Caledonia while the north normalizes from prior deficit.

From June through August, conditions will normalize overall. Surpluses will persist in a few pockets of Australia including the Lower Murray River region and the western edge of the Gibson Desert. Exceptional deficits are expected in Tasmania surrounding Lakes Pedder and Gordon. Nearly normal water conditions are forecast for New Zealand and New Caledonia.

The forecast for the final months – September through November – indicates that surpluses persist near the Gibson Desert and the Lower Murray River and moderate surpluses will emerge along Australia’s southeast coast.

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

IMPACTS
Converging storms over southeastern Australia forced the evacuation of 20,000 people after the region was deluged with over three feet of rain during a five-day period in March. The Hawkesbury River in New South Wales rose by more than 30 feet completely submerging the Windsor Bridge. Near Sydney the Warragamba Dam, source of the metropolis’ drinking water, overflowed, spilling enough water to fill 200,000 Olympic-size swimming pools. Flooding closed 200 schools. The Mid-North Coast region was particularly hard-hit by flooding and homeowners noted swarms of spiders scurrying up walls and snakes winding up trees in an effort to escape the high waters.

In New Zealand, however, the National Institute of Water and Atmospheric Research reports dry to very dry conditions in much of North Island with significant soil moisture deficit.

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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