Australia & New Zealand: widespread water surplus to persist in se australia

28 November 2022

THE BIG PICTURE
The 12-month forecast through July 2023 indicates widespread water surpluses in New South Wales and much of Victoria, Australia. Anomalies will be exceptional from the Middle Darling River in New South Wales reaching south past the Middle Lachlan River. In Victoria, moderate to severe surpluses are forecast across the state’s northern half, while extreme deficits are expected in a pocket on the coast in Cape Otway.

In Far North Queensland, some moderate surpluses are forecast in the Cape York Peninsula and the Atherton Tableland. Moderate surpluses are also expected in the Tiwi Islands in Northern Territory.

In Western Australia, surpluses will be intense in the Upper Avon River Catchment in the south, but deficits reaching exceptional intensity are predicted in coastal regions nearby from Perth to Albany. Deficits will also be intense in South Australia in pockets of the Eyre Peninsula, Kangaroo Island, and the Limestone Coast. Tasmania can expect widespread deficits in its western half and in the south where anomalies will be exceptional. A few pockets of moderate surplus are forecast on the island’s central east coast.

In New Zealand, moderate to severe deficits are forecast in Southland, becoming extreme in Fiordland. Elsewhere on South Island, a few coastal pockets in its northern half will see moderate surplus including the Banks Peninsula near Christchurch. On North Island, surpluses are forecast in the east and north. Some pockets of moderate surplus are expected in New Caledonia.

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

The forecast through January 2023 indicates that surpluses will continue to increase in a vast area through southeastern Australia and will emerge in northern Queensland (QLD). Surpluses will be widespread in the Murray-Darling Basin), extending to the coast and through most of Victoria (VIC). Anomalies will be exceptional in a broad path from the Middle Darling River past the Lachlan River, and around Lake Hume into VIC. In QLD, primarily moderate surpluses will emerge throughout the York Peninsula and coastal areas of the north. Moderate surpluses are expected in the Kiwi Islands of Northern Territory (NT). In Western Australia (WA), intense deficits will persist from Perth to Albany, and intense surpluses will persist in the Avon River region. Deficits in Tasmania will shrink and downgrade, while surpluses increase in the east. In New Zealand, moderate to extreme deficits are forecast in South Island’s southern tip, and moderate surpluses will linger near Christchurch and in eastern and northern North Island. New Caledonia will transition from deficit to moderate surplus.

From February through April, surpluses will shrink in southeastern Australia, retreating from coastal areas, but will remain widespread in the Murray-Darling Basin with persistent exceptional anomalies from the Middle Darling River well past the Lachlan. In VIC, surpluses will be extreme near Bendigo. Surpluses in Far North QLD will shrink considerably, persisting at the western edge of the Atherton Tableland and in the northern tip of the York Peninsula. Near-normal conditions will return to the Tiwi Islands. In WA, surpluses will continue in the Avon River region and deficits along the southwestern coast. Deficits will nearly disappear in Tasmania and a small pocket of surplus will persist on the central east coast. Deficits will shrink and moderate in southern New Zealand and surpluses will persist in the northeast and in New Caledonia.

The forecast for the final months – May through July – indicates persistent, intense surpluses from the Middle Darling River to the central border of VIC. A few pockets of exceptional deficit will emerge in southwestern Tasmania. Deficits will linger in a pocket of Southland, New Zealand and intensify.

Please note that WSIM forecast skill declines with longer lead times

IMPACTS
After heavy November rainfall, the small town of Eugowra, Australia was swept away during flash flooding that brought a tsunami of mud, tossing cars and leaving residents stranded on rooftops. The Wyangala Dam at the confluence of the Lachland and Abercrombie Rivers in the Center West region of New South Wales (NSW) breached its banks mid-month, inundating the small town of 800 residents and ripping buildings from their foundations.

Flooding throughout the state brought Australian Defense Force personnel in to support local responders, and New Zealand Fire and Emergency Services deployed specialists.

While not reaching the mines, floodwaters have cut off access to some coal mines, prompting one major mining operation to project lower production and higher unit costs in the upcoming year.

Several state highways on New Zealand’s North Island were closed due to flooding that tore up tree stumps and sent them bobbing along the highways. Power outages were also reported but repair crews were delayed seeking passable alternate routes.

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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