Australia & New Zealand: Water deficits will shrink in New Zealand

Australia & New Zealand: Water deficits will shrink in New Zealand

24 July 2020

THE BIG PICTURE
The 12-month forecast through March 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 some surpluses in the northeast, but deficits are forecast in the west and will be intense around Lakes Pedder and Gordon.

In Queensland, surpluses are forecast in the northwest corner of the Darling Downs and a small pocket of intense deficit is forecast on the northeast coast south of Cairns. Moderate deficits are forecast in Arnhem Land, Northern Territory; intense deficits south of Alice Springs in the center of the nation; and intense deficits along the southwest coast of Western Australia. Surpluses along with transitional conditions are expected in the Gibson Desert with moderate deficits to the west.

Moderate to severe deficits are expected in North Island, New Zealand, particularly north of Lake Taupo, and a few pockets of moderate deficit in South Island. Severe deficits are forecast for New Caledonia.

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

The forecast through September indicates the emergence of exceptional deficits in vast blocks of northern Australia from the Kimberley region and eastern Great Sandy Desert in the west into Northern Territory (NT) and spanning its northern border with Queensland (QLD). Exceptional deficits will also emerge in QLD’s Far North while prior exceptional deficits across the center of the state will disappear.

Widespread surpluses in southeastern Australia will shrink, persisting in the central Murray-Darling Basin in New South Wales (NSW). Surpluses will be extreme to exceptional between the Lachlan and Macquarie Rivers, and intense surpluses will persist between the mouth of the Murray in South Australia (SA) and the Victoria (VIC) border. Surpluses in the northwest Darling Downs of QLD will shrink and moderate. Deficits will intensify in VIC’s eastern tip and along the coast west of Melbourne. Anomalies in Tasmania (TAS) will shrink.

In the western reaches of the nation, transitional conditions are forecast west of the Gibson Desert in Western Australia (WA) and along rivers leading north. Prior widespread deficits in WA will retreat but deficits along the state’s southwest coastal tip will increase.

In New Zealand, deficits will shrink and downgrade overall but remain intense in North Island’s southern regions and in South Island between Christchurch and Dunedin. A pocket of moderate surplus is forecast near Lake Wakatipu in the Southern Alps. The extent of exceptional deficits will shrink in New Caledonia, but anomalies will be intense.

From October through December, much of Australia will return to normal conditions with intense deficits retreating completely. In the Murray-Darling Basin surpluses will persist, shrinking slightly in the Riverina region but emerging in some moderate pockets near Sydney. Surpluses in Darling Downs, QLD will shrink. At the mouth of the Murray intense surpluses will persist, and in the west exceptional surpluses will re-emerge at the western edge of the Gibson Desert and, with lesser intensity, along several rivers leading north and a path to the south. A slight uptick in moderate deficits is forecast for TAS. Conditions in New Zealand and New Caledonia will become nearly normal.

The forecast for the final months – January through March 2021 – indicates that surpluses will shrink and mild deficits will emerge down the center of Australia. Nearly normal conditions are expected in TAS, New Zealand, and New Caledonia.

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

IMPACTS
After nearly a year and a half of drought, the region encompassing Auckland, New Zealand finally got significant rainfall in July. Too much, in fact - nearly 200mm (7.87 inches) fell in 10 hours, breaching the banks of the Waiharakeke Stream in Northland, rendering roads impassable, and flooding local paddocks.

As damaging as the recent rains have been, the precipitation is not enough to offset months of dry conditions, says a MetService meteorologist. The downpours skirted Auckland’s biggest catchment, while its smallest overflowed. Overall, the region’s water storage is 58.3 percent compared to an 82.8 percent normal.

Water restrictions are likely to remain in place in Auckland well into 2021. Ironically, the area’s water infrastructure loses more water each day than restrictions save and losses could even be understated since drought conditions increase likelihood of pipe damage.

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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