Friday 31 August 2018

Australia's bleak prognosis for spring

Australia: Dry times to continue as BOM releases grim spring outlook
  • Drier than average spring likely for southern Australia and parts of the interior
  • Expect warm spring days
  • Dry and warm spring would mean intensification of drought and increase fire potential

30 August, 2014

The Bureau of Meteorology has released its latest climate outlook, and the forecast is grim.

It has been a dry summer, followed by a dry autumn, followed by a dry winter, for large parts of the country and it looks like spring is going to follow the trend.

The prolonged dry is starting to put a strain on water supplies, with some communities dealing with dam levels down to 10 per cent.

"Unfortunately for those that are having a close eye on rainfall, it does look likely that we're going to see a drier than usual spring," BOM Senior Climatologist Robyn Duell said

"So this is going to compound the already dry conditions that we've been experiencing across eastern Australia."

Ms Duell said it's been the driest start to the year New South Wales has seen since 1965.
"It's very comparable to some of the most severe rainfall deficits we've seen. It's been very unusually dry in the east."

Increased fire risk

For most of mainland Australia the warm and dry start to the year has led to dry soil moisture and dry vegetation.

"We've already seen some bushfires in New South Wales during August which is unusually early," Ms Duell said.

She said there are a lot of elements that go into bushfire risk but this spring's dryer and warmer outlook certainly has the potential to increase fire risk.

But while the drought has extended into parts of Queensland and Victoria, not everywhere has been dry.

Western Tasmania and south-west Western Australia have been very wet over the past few months.

Climate drivers

A Pacific Ocean phenomena with impacts around the world

The climate drivers are looking like they are just going to make things worse this spring.
The bureau currently has an El Nino watch in place, indicating there is twice the normal chance of El Nino, associated with dry conditions in the country's north and east, forming in the coming months.

But Ms Duell is not just focused on the Pacific.

"At the moment we're keeping quite a close eye to the north-west of Australia," she said.

"We've had cooler than usual water there for a little while and sometimes that can be the indication of the start of what we call the positive Indian Ocean Dipole event."

Ms Duell said cool water in the north-east can cause a change in the way frontal systems move across the south of the country.

"They often slip further south than they usually would," she said.

"That's something that we've been seeing happening through winter and that looks like it may continue to happen during spring."

Map of Australia with yellow and brown to the south, indicating dry conditionsPHOTO: Dry conditions are expected for Southern Australia and in parts of the interior, particularly in October.(Supplied: Bureau of Meteorology )
The outlook said low stream flows are expected to continue over the south-eastern mainland through October, thanks to predicted dry conditions on top of already dry soils.

Near median and high flows, however, could eventuate on the south-west coast of Western Australia and in Tasmania, where catchments are already primed following good winter rains.

What does this mean for water supplies?


According to the Bureau's water storage data, Sydney and Adelaide's water supplies are both well down on last year.

The situation varies greatly depending on where you are and how you are getting your water.

Generally the big city dams have a long way to go before they get into any real trouble.

"The Sydney situation is pretty good, but it's dry," WaterNSW spokesman Tony Webber said.

"The regions fluctuate from quite concerning to reasonably good."

But it is where people are relying upon water outside the dam system that things deteriorate.

"The dry land farming situation, where people are reliant on waterways not fed by dam storages, is actually quite dire," Mr Webber said.

Water New South Wales has Sydney's water capacity at 65 per cent, despite the dry catchments and low inflows.

Map of Australia covered mainly in yellow showing between 50 to 100 ml below average rainfall PHOTO: Autumn and winter have been dry for swathes of Australia. (Supplied: Bureau of Meteorology )

"The major dams that were talking about, even though we are seeing some storages falling below what we prefer, they are very large storages and they hold a lot of water," Mr Webber said.

"There is up to two years' supply, even under the worst case scenario, for the Sydney storages."

Variation in the regions

The overall capacity of the regional dams managed by WaterNSW is at 52 per cent, but according to Mr Webber that figure does not tell the whole story.

"In the south of the state, the dam storages that feed the Murrumbidgee are actually in quite a good situation, water security wise. Blowering and Burrinjuck Dams both are well stocked," he said.

"In the central regions of the state Wyangala Dam on the Lachlan River, which was the scene of that extensive flooding in 2016, it still sits at 59 per cent."
Others, like Burrendong Dam in the Macquarie Valley, which is at 32 per cent, are starting to feel the strain.
"The situation is getting a little bit tighter there, but they have very, very big storages. So that's still a long period of supply."

Who is running out of water?

A lone tree stands near a water trough in a drought-affected paddock.PHOTO: This drought-affected paddock on Jimmie and May McKeown's property is located on the outskirts of town of Walgett, supplied by the Keepit Dam. (Reuters: David Gray)
The real pinch points, according to Mr Webber, are the Keepit Dam in the state's north and the Menindee Lakes in the west.

Both are down around 10 percent of capacity and the outlook does not inspire a huge amount of hope in either case.

Menindee Lakes provides water for the nearby city of Broken Hill and also down the lower Darling river to the Murray.

Broken Hill only received 9.4mm of rain from the first of June to the 28th of August this year — just 18 percent of the average.

Mr Webber said if there are not any significant inflows into the lakes releases into the lower Darling may cease by December this year.

The aim is to hold supply for Broken Hill while a pipeline is built to link the town directly to the Murray River.

According to Mr Webber, the pipeline will be completed by the end of the year and will provide water security for Broken Hill.

But for Keepit there is no pipeline dream.
Mr Webber said Water NSW has been working with local landholders and communities to ensure essential human needs can be provided.

"Rather than releasing water subject to water orders from customers individually, it would really be just a more significant, perhaps a one-off or series of releases at an agreed time," Mr Webber said of a possible contingency plan should worse come to worst.

"So that people with basic stock and domestic access rights can top up their storage.

"Just to make sure they've got at least an extended water supply while we wait for the weather to change."

Mr Webber said the water security situation for most water customers is quite good but he does not want to give those suffering false hope.
"The dry land farming situation for farmers reliant on naturally occurring waterways is quite dire

New Zealand: NIWA

Seasonal Climate Outlook: 

Spring 2018

In New Zealand NIWA is a bit light-on-it and there has been nothing in the media.

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