Australia & New Zealand: Water surplus to increase in NSW

25 August 2022

THE BIG PICTURE
The 12-month forecast through April 2023 indicates moderate water surpluses in the Wide Bay-Burnett and South East (Brisbane) regions of Queensland. Surpluses are also forecast in eastern New South Wales in the Hunter Central Coast, Greater Sydney, and Central West regions, moderate overall but more intense in some pockets including the coast south of Sydney. In Queensland’s Far North, surpluses of varying intensity are expected north of the Holroyd River in Cape York Peninsula.

Elsewhere in Australia, surpluses are forecast in the Upper Avon River catchment of Western Australia, pockets of the Great Victoria Desert and Nullarbor Plain, the Tiwi Islands near Darwin in Northern Territory, and the Lower Murray River region of South Australia.

Deficits will skirt Victoria’s southern coast, extending west to Kangaroo Island. Exceptional deficits will dominate Tasmania’s western half, the Derwent Estuary, and Hobart. In Western Australia, moderate to severe deficits are expected on the southwest coast from Geraldton past Perth, becoming more intense as they reach Albany in the south.

In New Zealand, intense deficits are expected in South Island’s Fiordland, and surpluses in Christchurch and the northwest. In North Island, surpluses are forecast around the Bay of Plenty and in Northland where anomalies will be intense. Near-normal conditions are expected in New Caledonia.

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

The forecast through October indicates that widespread surpluses in eastern Australia will increase. Surpluses are forecast from Wide Bay-Burnett in Queensland (QLD) through eastern New South Wales (NSW) to Canberra. Anomalies will be moderate to severe and will reach inland to Dubbo and the confluence of the Macquarie and Barwon Rivers. Moderate surpluses are forecast on the Darling River. In northern QLD, a pocket of deficit is expected between Cairns and Townsville, but surpluses are forecast in the Atherton Tableland nearby. Surpluses will be widespread in Far North QLD north of the Holroyd River in Cape York Peninsula. A few intense pockets of deficit are forecast in coastal Top End, Northern Territory (NT) and the Kimberley in Western Australia (WA). Deficits will linger on WA’s southwest coast from the Lower Blackwood River to Albany while surpluses persist in the Avon River region and re-emerge in pockets of the Great Victoria Desert. Along Victoria’s coast, intense deficits will persist from Cape Otway past Melbourne. Widespread deficits will persist in Tasmania, intense in many areas including Hobart. Surpluses will linger in northern South Island, New Zealand and in Northland and on the Bay of Plenty in North Island. Severe deficits are expected in northern New Caledonia.

From November 2022 through January 2023, widespread surpluses will persist in eastern Australia, increasing past Canberra into East Gippsland, Victoria. Anomalies will be moderate overall but severe near Dubbo in NSW. Surpluses will increase in Far North QLD, and emerge in coastal Mackay (QLD), Top End, and the Fitzroy River region of the Kimberley. Deficits will shrink and downgrade considerably in coastal Victoria and Tasmania. Near-normal conditions are forecast in New Zealand. Moderate surpluses will emerge in central New Caledonia.

The forecast for the final months – February through April 2023 – indicates that surpluses will retreat from eastern Australia, but linger in pockets of the far north and in the Avon River region in the southwest. Surpluses in New Caledonia will increase.

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

IMPACTS
A storm hit New Zealand’s South Island in August, flooding the city of Nelson after the Maitai River burst its banks. In a deluge that the mayor described as a “one-in-100-year event,” military personnel were called in to assist as city streets flowed. Over 400 homes were evacuated and the main pipeline bringing water from a nearby reservoir to the city was damaged, disrupting the local water supply.

At the tip of North Island, flooding and landslides left one community completely cut off and 400 homes without power.

Water authorities in western New South Wales, Australia are closely monitoring the situation at Burrendong Dam on the Macquarie River (Wambuul River). The reservoir has been over 100 percent capacity for the past ten months and is currently at 136 percent, necessitating scheduled releases to mitigate spill threat while avoiding downstream flooding. A bridge in the riverside town of Dubbo is underwater and several areas of the Macquarie’s embankment have collapsed.

Water releases have been increased at the Burrinjuck Dam, also in New South Wales, as inflows from the Yass River reached the highest on record. With flooding possible from the planned spill, farmers are relocating livestock and a nearby caravan park has moved its permanent cabins for the first time in seven years. Some low-lying areas were already submerged, prompting rescues as roadways became impassable and motorists were stranded.

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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