Australia & New Zealand: Water deficits to persist in North Island NZ

Australia & New Zealand: Water deficits to persist in North Island NZ

22 May 2020

THE BIG PICTURE
The 12-month forecast through January 2021 indicates surpluses of varying intensity in the Murray-Darling Basin in southeastern Australia and at the mouth of the Murray in South Australia. Surpluses will reach exceptional intensity in South Australia between the Murray River and the Victoria border and in the Riverina area of New South Wales, particularly around Griffith. Tasmania can expect some surpluses in the northeast, including Flinders Island, but exceptional deficits are forecast in the southwest around Lakes Pedder and Gordon.

In Queensland, surpluses are forecast in the northwest corner of the Darling Downs; exceptional deficits in west Queensland’s Channel Country; and severe to exceptional deficits in the Gregory Range in Far North Queensland and coastal areas to the east, as well as the tip of the Cape York Peninsula. In Northern Territory, moderate to severe deficits are forecast for Top End and moderate surpluses in the upper basin of the Victoria River. In Western Australia, exceptional surpluses are forecast in the western Gibson Desert, and intense deficits in the Great Sandy Desert and coastal areas of the Kimberley region.

Moderate deficits are forecast in New Zealand along much of the east coast of South Island, but deficits will be more intense in the northern portion of the island and through North Island. Moderate deficits are forecast for New Caledonia.

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

The forecast through July indicates that widespread surpluses of varying intensity will persist in the Murray-Darling Basin of southeastern Australia, extending south to the coast at Melbourne. Surpluses will be primarily moderate along the paths of the Murray and Darling Rivers but will reach extreme to exceptional intensity in the central Macquarie River Catchment; near Griffith in the Riverina area; and from the mouth of the Murray in South Australia (SA) to the Victoria (VIC) border. Surpluses will shrink and downgrade in Tasmania and deficits will nearly disappear. In Queensland (QLD), surpluses in the northwest corner of the Darling Downs will downgrade.

Conditions in the center of the country will become nearly normal as intense deficits disappear but exceptional deficits will emerge in the north in pockets of Far North Queensland; in Top End, Northern Territory (NT) between the Katherine and Roper Rivers; and spanning the northern border of Western Australia (WA) and NT in the Ord River region. Some moderate surpluses will emerge nearby in the upper Victoria River region. Exceptional surpluses will persist in the western Gibson Desert in WA and surpluses will re-emerge along rivers leading north and along a broken path to the south.

In New Zealand, deficits will remain widespread on North Island and will reach exceptional intensity in the Waikato River region. Deficits in South Island will shrink slightly but will persist on the east coast and in the north. Deficits in New Caledonia will moderate overall.

From August through October, surpluses will persist in the Murray-Darling Basin, shrinking in VIC but increasing near Adelaide. Surpluses will persist with intensity in the western Gibson Desert in WA, shrink in the northwest corner of the Darling Downs in QLD, and nearly disappear in Tasmania. Exceptional deficits remain in the forecast for pockets of Far North Queensland; will increase in Top End, NT, emerging throughout Arnhem Land; and will retreat from the Ord River region of WA but emerge in western Kimberley. Water conditions will normalize in much of New Zealand, leaving a few areas with moderate anomalies. Deficits will continue to shrink in New Caledonia with some relatively mild anomalies lingering.

The forecast for the final months – November through January – indicates that surpluses will persist in southeastern Australia and in WA in a pattern and with intensity similar to the forecast through October. Deficits across northern Australia will disappear and moderate surpluses will emerge in Top End, NT and Far North Queensland. Nearly normal conditions are forecast for New Zealand and New Caledonia.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
Adelaide, Australia recorded its wettest April in 20 years, causing some minor flooding at the end of the month. Flood warnings were issued for 11 rivers across the state of Victoria and emergency responders received nearly 300 calls for assistance. In the neighboring state to the north, New South Wales recorded its wettest April since 2015, according to the Australian Bureau of Meteorology.

In mid-April, the waters of the Murray and Darling Rivers flowed together for the first time in two years, an event heralded by farmers in the region. But despite the recent increase in rainfall, the Murray-Darling Basin storage was at just a third of capacity at mid-May.

In New Zealand, a different water scenario has been unfolding: severe deficits. For the first time in over 25 years, as of 17 May the drought-stricken Auckland area of North Island is under water restrictions, prohibiting outdoor water use. The region’s January through April rainfall was the driest on record with vegetation stress clearly visible in satellite images.

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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