Australia & New Zealand: Widespread deficits will retreat

Australia & New Zealand: Widespread deficits will retreat

24 September 2020

THE BIG PICTURE
The 12-month forecast through May 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 moderate to extreme in New South Wales between the Lachlan and Macquarie Rivers and exceptional in South Australia between the mouth of the Murray and the Victoria border, along with transitional conditions.

Tasmania can expect exceptional deficits in the west and from Hobart along the Derwent Estuary. Some pockets of intense deficit are also forecast on Victoria’s western coast and on Kangaroo Island in South Australia and along that state’s coast. In northern Queensland, a small pocket of intense deficit is expected on the northeast coast south of Cairns. At the opposite corner of the nation, severe to exceptional deficits are forecast on Western Australia’s southwest coast, including in the region’s capital, Perth. Intense surpluses are forecast for the Upper Swan River region east of Perth. Transitional conditions are expected spanning the western edge of the Gibson Desert leading to moderate deficits.

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. Severe deficits are forecast for New Caledonia.

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

The forecast through November indicates that widespread exceptional deficits in Australia and New Zealand will retreat, leaving a few pockets. Eastern Australia can expect primarily normal water conditions with surpluses of varying intensity in the central Murray-Darling Basin between the Macquarie and Lachlan Rivers and moderate surpluses along the southeast coast in New South Wales from Sydney to Victoria’s border. Deficits are forecast along Victoria’s western coast, and deficits in Tasmania will moderate. At the mouth of the Murray River in South Australia, surpluses will be intense though transitional conditions are forecast further inland. In Queensland, moderate surpluses will re-emerge at the northwestern edge of the Darling Downs and a pocket of intense deficit will persist on the northeast coast near Cairns.

Deficits are forecast in Top End, Northern Territory, primarily moderate, and some areas of moderate surplus are expected in the Upper Victoria River region and the central Barkly Tableland. In Western Australia, exceptional deficits are forecast at the eastern edge of the Great Sandy Desert, and some paths of surplus in the Gibson Desert along with mixed conditions, with moderate deficits farther west. In the southwest corner of the state, deficits are forecast on the coast, moderate near Perth but exceptional farther south near Busselton. Surpluses are forecast for the Upper Swan River region nearby.

In New Zealand, deficits and surpluses will shrink considerably, leaving deficits along the eastern coasts from Hawke’s Bay in the north to Dunedin in the south, and some surpluses primarily north of Auckland. Though downgrading, deficits in New Caledonia will be extreme.

From December 2020 through February 2021 much of Australia will return to normal conditions. Surpluses will persist between the Macquarie and Lachlan River, downgrading somewhat; moderate surpluses in the coastal southeast will shrink; and surpluses and transitional conditions are forecast at the mouth of the Murray. Deficits will nearly disappear in Tasmania and will downgrade in coastal Victoria. Deficits will shrink slightly in Australia’s southwestern tip and surpluses will persist in the Upper Swan River. Intense surpluses will re-emerge across the western edge of the Gibson Desert. Nearly normal conditions are forecast for New Zealand and New Caledonia.

The forecast for the final months – March through May 2021 – indicates surpluses in the west near the Gibson Desert and in the Upper Swan River region, and deficits near Busselton. Deficits will increase slightly on Victoria’s coast west of Melbourne and moderate surpluses will emerge in New Caledonia.

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

IMPACTS
As of mid-September, the water stored in dams around Auckland, New Zealand was around 20 percent less than the average for this time of year. Drought in the region prompted Stage 1 water restrictions to be instituted in May which remain in effect, prohibiting residential use of outdoor water. The region’s water utility has been granted permission to draw an additional 100 million liters of water per day from the Waikato River to meet demand.

In the Hauraki District of the Waikato region, a mayoral drought relief fund distributed $265,000 (US $174,420) to farmers, though claims totaled $860,000 (US $562,797).

Winter crop forecasts for Australia are looking up after rainfall in some regions has eased prolonged drought conditions. National production is expected to increase by 65 percent this fiscal year, 20 percent above the 10-year average. Estimates are even rosier for New South Wales where experts predict a 300 percent increase over last year. Canola production across the nation could increase by 50 percent. However, Australia’s Bureau of Meteorology warns that nationwide water storage won’t return to normal until the country sees sustained, above-average rainfall, which the predicted La Niña could bring.

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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