The Big Picture
Water deficits are forecast to linger for the next six months across parts of northern Australia – particularly Arnhem Land and along the Gulf of Carpentaria – and also from Perth southward; in Tasmania; on North Island, New Zealand; and in New Caledonia.

Impacts
Large-scale, unprecedented dieback of mangrove trees in Queensland's Gulf of Carpentaria has scientists puzzling over possible causes. One theory put forth by Norm Duke, a professor at James Cook University and spokesman for the Australian Mangrove and Saltmarsh Network: "It is coincident with a very hot dry period in northern Australia, in some ways it is coincident, in the same season at least, with the dieback of corals on the east coast." Mangroves help prevent shoreline erosion, store carbon, and provide fish habitat. Some fisherman in Karumba on the Gulf of Carpentaria have reported a drop in catches.

With recent record dry years, water officials in Perth, the capital of Western Australia, are looking at plans that reduce reliance on dam flows, including a water conservation campaign, increased withdrawals from aquifers, and increased water recycling.

Now in their second year of drought, farmers in North Canterbury, New Zealand are sending their cattle and sheep out of the district for grazing and are seeking other employment. A normal year's rainfall in the area is 700mm but the last 12 months have brought only 230mm.

Forecast Breakdown
The 3-month composite (below) for the same 12-month period shows the evolving conditions in more detail. Deficits across much of Australia are forecast to diminish in May with the exceptions mentioned above. A transition from moderate deficits to moderate surpluses in the Darling and Murray Rivers and their tributaries is forecast to begin in August and continue through January. Current surpluses farther north in eastern Queensland are expected to persist, and surpluses are forecast to emerge along the Barcoo River and Cooper’s Creek in November.

In North Island, New Zealand exceptional deficits will persist through June, and pockets of moderate to severe deficits will continue to emerge on South Island in the following months. Exceptional and widespread deficits in New Caledonia are forecast to diminish in May and thereafter, though deficits will continue to emerge through October.

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

Comment

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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