Australia & New Zealand: Water deficits to persist in Tasmania

23 October 2020

THE BIG PICTURE
The 12-month forecast through June 2021 indicates surpluses in a pocket of the central Murray-Darling Basin in southeastern Australia and at the mouth of the Murray. Surpluses will be moderate to extreme between the Lachlan and Macquarie Rivers in New South Wales and exceptional between the mouth of the Murray and the Victoria border in South Australia.

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Tasmania can expect exceptional deficits in the west and from Hobart along the Derwent Estuary. Some pockets of intense deficit are also forecast along Victoria’s west coast and on Kangaroo Island in South Australia and along that state’s coast. In Western Australia, exceptional deficits are forecast along the southwest coast from Geraldton through Perth and past Busselton and the Lower Blackwood River region. Surpluses are forecast from the Upper Blackwood River region through the Avon River region east of Perth. The Gibson Desert will also see surpluses including exceptional anomalies spanning its western edge and some transitional conditions. In Northern Territory, a pocket of moderate surplus is forecast east of the Victoria River.

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. Mixed conditions are forecast in New Caledonia.

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

The forecast through December indicates that much of Australia will return to near normal conditions as widespread, exceptional deficits retreat. Deficits will persist along the nation’s southwest coast; anomalies will be moderate near Perth but increasingly intense further south through Busselton and the Lower Blackwood River region. Surpluses are expected nearby in the Avon River region and anomalies will reach exceptional intensity. Intense surpluses are also forecast in the Gibson Desert of Western Australia and spanning its western reaches with anomalies of lesser intensity creating paths leading both north and south. In the east, surpluses will persist in the central Murray-Darling Basin between the Macquarie and Lachlan Rivers in New South Wales and from the mouth of the Murray in South Australia to the Victoria border. Some moderate surpluses will persist in Queensland at the northwestern edge of the Darling Downs. Deficits will downgrade on Victoria’s western coast and in Tasmania, while remaining intense near Hobart and in the Derwent Estuary.

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In New Zealand, deficits and surpluses will shrink considerably, leaving deficits along the eastern coasts from Hawke’s Bay in the north and between Christchurch and Dunedin in the south. Surpluses will moderate on the points framing the Bay of Plenty on North Island. Deficits in New Caledonia will shrink and moderate.

From January through March 2021, deficits will shrink in Australia’s southwestern tip, become mild in Tasmania, and some relatively mild deficits will persist along Victoria’s west coast. Surpluses will persist in the west in the Avon River region and spanning the southwest corner of the Gibson Desert. Some pockets of moderate surpluses will emerge east of the Victoria River in Northern Territory and in the Cape York Peninsula in northern Queensland. Surpluses will shrink in the central Murray-Darling Basin, transitional conditions will persist at the river’s mouth, and moderate surpluses will increase near Canberra. Nearly normal conditions are expected in New Zealand and New Caledonia with some pockets of surplus.

The forecast for the final months – April through June 2021 – indicates nearly normal conditions for much of the region with pockets of surplus in the Avon River region, southwest of the Gibson Desert, in Northern Territory, at the mouth of the Murray River, and in New Caledonia.

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

IMPACTS
The Australian government has earmarked funds from its AU $5 billion (US $3.57 billion) Future Drought Fund for development of an interactive website for farmers to assess risk and impact. The site, DR SAT, will integrate existing online tools and deploy new capabilities to address knowledge and assessment gaps.

Though increased precipitation has brought some green back into the pasturelands of New South Wales, some water restrictions remain in place as communities wait for reservoirs to fill. In the Murray-Darling system, the Burrendong Dam serving Dubbo was at 46.6 percent capacity in early October, up from 3 percent in the summer; but the Chaffey Dam serving Tamworth was at just 26 percent after being nearly drained. Few are celebrating just yet, as many farms in the area have gone several successive years without income due to the drought.

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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