Australia & New Zealand: Water deficits to emerge in northern Australia

Australia & New Zealand: Water deficits to emerge in northern Australia

19 August 2020

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

Tasmania can expect intense deficits in the west, exceptional around Lakes Pedder and Gordon. Some pockets of intense deficit are also forecast on South Australia’s Kangaroo Island and along the state’s central coast.

In Queensland, some moderate surpluses are forecast in the northwest corner of the Darling Downs and a small pocket of intense deficit is expected on the northeast coast south of Cairns.

Along the southwest coast of Western Australia, severe to exceptional deficits are forecast, including in the region’s capital, Perth. Surpluses and transitional conditions are expected in the Gibson Desert with moderate deficits to the west.

In New Zealand, surpluses are expected north of Auckland and deficits northeast of Wellington on North Island. Some moderate deficits are expected along South Island’s coast between Christchurch and Dunedin. Severe deficits are forecast for New Caledonia.

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

The forecast through October indicates the emergence of exceptional deficits in large pockets across the northern reaches of Australia including Far North Queensland (QLD); Arnhem Land in Top End, Northern Territory (NT); and parts of the Kimberley Plateau in the northern portion of Western Australia (WA). Moderate surpluses will linger in the upper reaches of the Victoria River in NT. A vast area of exceptional deficit in central QLD will retreat completely and surpluses will re-emerge in the northwest Darling Downs.

Surpluses in southeastern Australia will shrink, persisting mainly in the central Murray-Darling Basin in New South Wales (NSW), and will be extreme to exceptional between the Lachlan and Macquarie Rivers. Intense surpluses will persist between the mouth of the Murray in South Australia (SA) and the Victoria (VIC) border. Northeastern Tasmania will normalize, and deficits elsewhere will shrink considerably but persist with intensity around Lakes Pedder and Gordon. A small pocket of exceptional deficit will emerge on VIC’s western coast.

In SA and WA, areas of prior deficit will normalize or downgrade to mild deficit, though intense anomalies will persist around Busselton in WA’s southwestern tip, moderating as they reach north to Perth. Some pockets of surplus will persist in southwestern WA in the Upper Swan River area and in the center of the state on seasonal rivers leading from the Gibson Desert where exceptional surpluses will re-emerge.

In New Zealand, deficits will shrink considerably but remain intense in pockets. Surpluses are forecast north of Auckland. Deficits will downgrade but will be extreme in New Caledonia.

From November 2020 through January 2021, much of Australia will return to normal conditions. Surpluses will persist in the central Murray-Darling Basin, downgrading slightly, and will persist with intensity at the mouth of the Murray. Moderate surpluses are expected to emerge along Australia’s southeast coast from Sydney. Nearly normal conditions are forecast for Tasmania. In the nation’s western half, surpluses will persist near the Gibson Desert and along ephemeral rivers leading away. Surpluses will also persist in pockets of southwestern WA including in the Upper Swan River area. In New Zealand and New Caledonia, conditions are expected to be nearly normal.

The forecast for the final months – February through April 2021 – indicates that surpluses will shrink, moderate deficits will emerge in the Buckland Tableland of QLD, and mild deficits will emerge down the center of Australia. Nearly normal conditions are expected in Tasmania, New Zealand, and New Caledonia.

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

IMPACTS
Heavy rainfall hammered Australia’s south coast in New South Wales and ACT (Australian Capital Territory) over several days from late July into August with some regions reporting as much as 300 millimetres (11.8 inches) in 24 hours. A surfer died in Sydney and a kayaker perished near Canberra on the Murrumbidgee River. The storm canceled ferry service in Sydney and evacuation orders were issued for several communities farther south. The Australian Bureau of Meteorology called it the region’s worst flooding in nearly three decades.

Lack of rainfall in Auckland, New Zealand is causing structural damage to some homes as the dry ground beneath them shifts. After the driest January through April ever recorded in the city, Auckland has been under water restrictions since 16 May. Amid complaints about his handling of the water crisis, the CEO of Auckland’s water utility resigned in mid-August from what was the highest paying position in the city government.

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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Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.25°x0.25° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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