Australia & New Zealand: Water deficits forecast to persist in Queensland

28 March 2017

The Big Picture
The 12-month composite map (below) indicates severe to exceptional water deficits in Australia’s eastern half, and surpluses in the northern part of the western half. Moderate to severe deficits are forecast for Tasmania; North Island, New Zealand; and New Caledonia.

Impacts
The total drought-affected area in Queensland reached a record 87 percent, says the state's Agricultural Minister, the highest ever. Conditions have resulted in the loss of paddock roughage in many areas and an increase in the number of producers applying for individual droughted property status.

New CSIRO research - the federal government agency for scientific research - points to climate change as the cause of flat-lining in Australia's wheat production since 1990. Wheat yield tripled from 1900 to 1990 but has stagnated thereafter, despite 2016's record harvest. The study found that average maximum temperatures increased by more than 1 degree over 26 years during crop-growing months, while rainfall declined by 28 per cent. Even with significant productivity gains in recent decades, those gains are only cancelling out negative climatic changes.

An unprecedented massive die-off of mangrove forest along the Gulf of Carpentaria in northern Australia over just one month in early 2016 has been attributed to record temperatures, prolonged drought, and El Niño, says the head of the Mangrove Research hub at James Cook University. The loss of about 7,400 hectares (18,289 acres) of mangrove could have multiple impacts: loss of fisheries valued at hundreds of millions of dollars, an increase in coastal erosion due to loss of forest barrier, and poorer water quality without forest filter.

Flooding has taken a toll in parts of Australia including Kimberley in the northwest, Swan Valley in the southwest, and New South Wales in the southeast. A kayaker was rescued after spending an hour clinging to a tree when her kayak overturned in flooded Fitzroy Crossing during Kimberley's wettest summer ever recorded. Western Australia's Swan Valley was declared a disaster zone after flooding cause an estimated AUS$10 to $15 million in damages (US$7.67 to $11.5 million) to the region's wine growers. Around 1,500 people in northeast NSW were cut off as heavy rainfall flooded rivers.

Forecast Breakdown
The 3-month maps (below) for the same 12-month period show the evolving conditions.

As is apparent in the top two maps, water anomalies – both deficits and surpluses – are forecast for much of Australia for the six-month period ending May 2017. Thereafter, the extent and severity of anomalies is expected to diminish considerably.

Overall, the extent of exceptional deficits will diminish March through May; widespread exceptional deficits in South Australia will nearly disappear leaving moderate deficits. However, widespread deficits of varying severity are forecast in eastern Australia, particularly Queensland, with exceptional deficits in Central West, Queensland. Primarily moderate deficits are forecast for New South Wales, much of Victoria, and in Western Australia south of Perth. Deficits in New Caledonia and North Island, New Zealand are expected to diminish. Surpluses in the northern part of Western Australia will diminish in severity.

The forecast for June through August indicates considerable improvement with the near-absence of extreme to exceptional deficits. Primarily moderate deficits are forecast in southeastern Australia from Adelaide to Canberra, and across the north from the southern shore of the Gulf of Carpentaria through Cape York Peninsula. More intense deficits are forecast to persist in the western portion of Northern Territory’s Top End near Darwin. Deficits will continue to emerge south of Perth and are forecast to be severe. Likewise deficits will continue to emerge in Tasmania with severe deficits in the east, and moderate to severe deficits are forecast for northern South Island, New Zealand, and eastern North Island.

The final months – September through November – indicate a forecast similar to the prior three months.

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