Australia & New Zealand: Water surpluses will persist in E Australia

19 April 2022

THE BIG PICTURE
The 12-month forecast through December indicates widespread water surpluses in eastern Australia from Rockhampton, Queensland through eastern Victoria. Anomalies will be widespread in New South Wales reaching extreme to exceptional intensity in the North Coast region and around Sydney, as well as in East Gippsland, Victoria.

Deficits are expected across northern Australia, intense in some regions. Deficits will be severe to exceptional in the Hammersley Range and Kimberley region of Western Australia, the Victoria River catchment and along the Gulf of Carpentaria in Northern Territory, and the Gregory Range and a pocket north of Townsville in Queensland.

In the nation’s southwest corner, severe to exceptional water surpluses are forecast in the Avon River catchment leading south, and deficits will skirt the coast from Busselton to Albany.

Severe to exceptional deficits will dominate western Tasmania, the Derwent Estuary, and Hobart.

In New Zealand, deficits of varying intensity are predicted for South Island’s southern half. Anomalies will be exceptional in Southland. Surpluses are expected in North Island from Wellington through East Cape. In New Caledonia, moderate surpluses are forecast in the south.

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

The forecast through June indicates that while downgrading, surpluses will remain widespread in eastern Australia from just south of Rockhampton on Queensland’s coast through the Murray-Darling Basin and coastal regions into East Gippsland, Victoria. Anomalies will be moderate to severe and will include widespread, severe surpluses near Sydney and moderate surpluses on the Lachlan River. Western Australia will see intense surpluses re-emerge in the greater Avon River catchment leading south. Deficits will increase in Tasmania with exceptional deficits persisting in Hobart and the Derwent Estuary. In New Zealand, deficits will increase in South Island’s southern half as they creep north, and anomalies will be exceptional in Southland and nearby Stewart Island. Northern coastal areas of the island can expect surpluses. Across Cook Strait in North Island, surpluses will shrink and downgrade, persisting from Wellington through East Cape. Surpluses are also forecast in the southern half of New Caledonia.

From July through September, surpluses in eastern Australia will shrink somewhat in Queensland but will remain widespread in eastern New South Wales, increasing between Dubbo and Armidale where anomalies will be severe. Moderate surpluses will persist on the Lachlan River and emerge on the Darling, and surpluses in East Gippsland, Victoria will shrink and moderate. Across northern Australia deficits will emerge, exceptional in the Kimberley region of Western Australia; near Darwin, the Victoria River Watershed, and east Arnhem Land in Northern Territory; and some pockets of Far North Queensland including the Upper Mitchell River region. Surpluses Western Australia’s Avon River Watershed will shrink. In Tasmania, deficits will persist, downgrading in Hobart but intensifying around Lakes Gordon and Pedder. Anomalies in New Zealand will shrink considerably with some lingering deficits in South Island and lingering surpluses in Hawke’s Bay and East Cape, North Island.

The forecast for the final months – October through December – indicates that surpluses will increase in eastern Australia and will emerge throughout the Cape York Peninsula in Far North Queensland and in coastal Top End, Northern Territory. Deficits will retreat from northern Australia but linger in southern Tasmania, and increase somewhat in South Island, New Zealand. Surpluses are forecast throughout New Caledonia.

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

IMPACTS
Heavy rainfall continued to pummel eastern Australia, dumping a month’s worth on the metropolis of Sydney overnight on 7 April, downing power lines and inundating streets.

The government of New South Wales has begun to distribute temporary housing pods to accommodate victims of flooding in March, earmarking AU $350 million (US $258 million). Another AU $67 million will help get flood-stricken schools repaired, educational equipment and supplies replaced, and will provide counseling for students and teachers.

Last month as the floods came, oyster farmers in the Macleay River region of New South Wales fretted over the shipment of baby oysters that had just arrived, fearful that flood-acidified waters would destroy their calcium-based shells and that saltwater, necessary for development, would be “sweetened.” The National Marine Science Center offered to babysit the oysters until their native waters normalized.

New Zealand’s southern region is experiencing the lowest rainfall levels since record-keeping began 50 years ago. The official drought designation in Otago will release up to AU $100,000 in farm relief funding

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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