Australia & New Zealand: Water deficits will persist south of Perth

Australia & New Zealand: Water deficits will persist south of Perth

26 February 2021

THE BIG PICTURE
The 12-month forecast through October 2021 indicates pockets of surplus, primarily moderate in southeastern Australia. Surpluses will follow the coast of New South Wales passing through Sydney, and pockets of surplus are forecast in the Murray-Darling Basin - north of Dubbo and in the Middle Lachlan River region and in Victoria southeast of Wangaratta. Exceptional surpluses are forecast near the Lower Murray River in South Australia. In Tasmania, however, deficits are forecast in the south and will be severe near Hobart and in the Derwent Estuary.

In northern Queensland, moderate to severe deficits are forecast along the coast between Cairns and Townsville and west to the Gregory Range. Surpluses are expected in a belt across the Cape York Peninsula. Elsewhere in Australia’s north, moderate surpluses are forecast in the Victoria River region of Northern Territory.

In Western Australia, exceptional deficits are forecast in the southwestern tip near Busselton and the Lower Blackwood River region, downgrading as they reach north past Perth and south towards Albany. Intense surpluses are expected in the southern Avon River Basin and a pocket north of Esperance. Surpluses will also be intense in a large pocket spanning the western edge of the Gibson Desert with anomalies of lesser intensity trailing into the western region of the Great Victoria Desert. Some scattered pockets of moderate surplus are forecast in South Australia and a pocket in the Simpson Desert in the center of the nation.

In New Zealand, scattered deficits are forecast on South Island, severe between Christchurch and Dunedin. Surpluses are expected in eastern New Caledonia and moderate deficits in the central region.

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

The forecast through April 2021 indicates that deficits will retreat though a small path will persist along Australia’s southwestern coast from Perth to Albany and will include exceptional anomalies. Surpluses will persist in the Avon River Basin in the southwest and in a pocket north of Esperance. Intense surpluses will re-emerge at the western edge of the Gibson Desert. In the north, surpluses will nearly disappear south of the Kimberley Plateau and in Arnhem Land, Northern Territory, but will persist in the Victoria River region. In northern Queensland, surpluses in the Cape York Peninsula will persist but downgrade to mild in some regions.

In southeastern Australia, surpluses will shrink near Armidale, retreat between the Darling and Lachlan Rivers, and persist in Riverina. Moderate surpluses will increase somewhat in pockets of Victoria, particularly in the Australian Alps, and intense surpluses will re-emerge near the Lower Murray River in South Australia. Deficits will persist west of Melbourne on Victoria’s coast. Conditions in Tasmania will begin to normalize. In New Zealand, surpluses will retreat as scattered mild to severe deficits increase. Moderate surpluses are forecast in New Caledonia’s south while the north normalizes from prior deficit.

From May through July 2021, surpluses will persist in the Victoria River region of Northwest Territory and a pocket near the Gibson Desert, but will shrink in the Avon River region in the southwest. Areas of prior deficit in the southwestern tip will normalize. Most areas of prior surplus in southeastern Australia will transition to normal or mild surplus though anomalies will remain intense near the Lower Murray River and moderate surpluses will emerge along the coast from Sydney to the Victoria border. In Tasmania, exceptional deficits will emerge around Lakes Pedder and Gordon. Water conditions are expected to be nearly normal in New Zealand and New Caledonia.

The forecast for the final months – August through October 2021 – indicates that surpluses will emerge along the Darling River and widespread surpluses will emerge throughout eastern New South Wales.

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

IMPACTS
Dry conditions in New Zealand have created shortfalls in the nation’s hydro-electricity production. Storage is 2000 GWh below levels at the same time in 2020, which was New Zealand’s driest recorded winter. NZ’s energy utility company, Genesis, will bring a shuttered coal-fired unit online to supplement electricity supply.

With grape harvest season approaching in New Zealand’s wine-growing region, fire officials have advised vineyards against using “bird-bangers,” gas-generated machines used to frighten birds away, citing dry conditions where an errant spark could set off a field fire.

Australian corn processors are relying on imported corn from Thailand to fill orders due to a combination of drought-impacted native harvests over the past several years and COVID-19 panic hoarding by the public.

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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