AUSTRALIA & NEW ZEALAND: WATER DEFICITS TO DOWNGRADE BUT PERSIST IN TASMANIA

23 May 2018

THE BIG PICTURE
The 12-month forecast (below) shows a large block of exceptional water deficits in Northern Territory leading north and spreading along the southern shore of the Gulf of Carpentaria. Intense deficits are also forecast near Darwin in the north and the nearby Daly River region, in a few pockets along Victoria’s coast, and in Tasmania.

Areas of moderate to extreme deficits include a large block in Australia’s interior, northern and eastern Kimberley region in Western Australia, the country’s southwest tip, and New Caledonia.

Surplus conditions are expected in a pocket of the southwest coast of Kimberley region, around the Mackenzie River in eastern Queensland (QLD), and in the Atherton Tablelands of northern QLD.

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

As is apparent in the map series, the forecast indicates that exceptional deficits which dominated a vast stretch of southern Australia in the prior three months will disappear. Deficits are forecast across northern Australia, in the southwest, in the southeast, and in Tasmania. These deficits are expected to be intense in Tasmania, the southwest tip of Australia, in Darwin and the Daly River region of Northern Territory (NT), along the southern shore of the Gulf of Carpentaria, and in pockets along the southeast coast from Melbourne to Brisbane. Moderate deficits are expected along the Darling, Lachlan, and Macquarie Rivers in New South Wales. Moderate to severe deficits are forecast for New Caledonia. Surpluses will shrink but persist in the Mackenzie River region and the Atherton Tablelands of QLD, and in southwest Kimberley region of Western Australia (WA).

From August through October deficits will downgrade in Tasmania but remain intense in some areas, will shrink and moderate in southwestern Australia, and will nearly disappear in the southeast. Deficits remain in the forecast for northernmost regions of Australia and are expected to be intense around Darwin and eastern Arnhem Land in NT, and northern Cape York Peninsula QLD. Surpluses will continue in the Mackenzie River region QLD and will expand in southwest Kimberly region WA. Moderate to severe deficits will continue in New Caledonia, and some moderate deficits are expected to emerge in southern New Zealand.

The forecast for the final months – November through January – indicates primarily mild anomalies in the region.

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

IMPACTS
Struggling cattle farmers in New South Wales, Australia are preparing to walk off their farms if the government fails to implement drought assistance subsidies soon. The government has not proclaimed a drought in cattle-producing areas of Australia, precluding any public aid from being distributed to farmers. Lack of fodder has forced many to sell off a majority of their herd including critical breeding stock.

Western Australia, which typically produces over 40 percent of the national wheat crop, received only 27 percent of its average rainfall over March and April, forcing wheat farmers to plant in dry soils and hope for rain. Eastern wheat farm soils, meanwhile, are at their lowest moisture levels in five years.

Recent research, using multi-century rainfall reconstruction, found that major droughts in southern Australia in recent decades are likely the most extreme that the continent has experienced over the past 400 years.

Floodwaters from record rainfall in southern Tasmania - over 100 millimeters (~4 inches) in one day - caused damages amounting to over $20 million (USD $15 million) in insurance claims. Flash flooding turned the main street of Hobart into a river, pushing cars, mud, and debris through the central business district. North of the city, rushing water collapsed multiple bridges, cutting off road access to several small communities. Some residents, meanwhile, have been out of their homes since a 2016 flooding event caused residential damages that are still being negotiated with insurance companies.

Farmers on Tasmania’s east coast, however, celebrated the rain, which brought some relief amid a harsh drought that has left farm reservoirs empty, forced farmers to de-stock cattle herds, and prompted official water use restrictions. 

Two tropical cyclones, Jose and Keni, struck the island nation of Fiji within one week in late April, causing landslides and $12 million (USD $5.8 million) in road damages. At least 8 people were killed in the storms and over 1,500 homes were damaged.

Researchers from Australian National University are warning that Melbourne's water supply could be threatened in the coming years by forest collapse in Victoria's central highlands due to logging and bushfires. About 61 percent of the trees have been felled in the catchment that feeds Melbourne's largest reservoir and provides water for many of the city's 4.5 million inhabitants. 

New Zealand's annual glacier snowline survey has revealed that the summer heatwave triggered one of the largest glacier melt seasons since records began in 1977. Over the last 40 years, scientists estimate that the glaciers have lost 30 percent of their ice.

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 0.5°x0.5° 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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