Australia Weather News

The crystal clear waters of the Disappearing Tarn on Hobart's kunanyi/Mount Wellington are back after last week's heavy rainfall, with reports levels are at the deepest for several years.

As Hobart residents awoke to a deluge on Friday which saw widespread flooding, water was rising in a rocky crevice on the southern slopes, heralding the tarn's return.

The phenomenon is a favourite of professional nature photographers and social media snappers.

It is not easily found — there are no signs and only keen bushwalkers can readily spot it.

Bushwalker James Spencer trekked the six kilometres to the tarn on Saturday, on his third visit to capture it.

"After the huge rains on Thursday night, I knew there was a pretty good chance the tarn would be filled," he said.

"I got my partner and a friend of mine and off we went up the mountain."

Much of the mountain is now off limits to the public, but on Saturday about 30 people visited the tarn.

"The colour of the water is incredible and it's such a different thing to any other lake you see in Tassie," he said.

"It's an amazing shade of blue."

Social media bringing the shutterbugs

Mr James said it had changed since his last visit in 2016.

"The water was definitely higher for sure [this time], but also as a sign of Tassie's increasing popularity, there was about 30 people there," he said.

"Two years ago there was nobody there, it was just me and my mates.

"It's interesting to see how much more popular it's got as a result of word of mouth, exposure and Instagram and all of that," he said.

Easterly weather a key to reappearance

Wilderness tour guide Cody McCracken said the tarn was especially deep at the weekend.

"Certainly looking at some of the photographs that I've seen coming out of Instagram, it's certainly the fullest I've ever seen," he said.

"There's not a heap of scientific literature out there that explains exactly why it occurs.

"We certainly know it occurs in high rainfall events, anywhere in excess of 60 millimetres over the course of a day or a couple of days, and it's generally associated with more easterly weather and east coast lows."

Bureau of Meteorology forecaster Matthew Thomas said he had heard accounts about the tarn reappearing.

"I've never been there, I've never seen it, I've just heard people talk about it in bushwalking terms that there is this lake you can visit at certain times after heavy rain," he said.

"I would assume that it's possibly something to do with the fact there's a slight depression that fills up with water when there's large amounts of rainfall up there."

Safety concern puts tracks off limits

The Hobart City Council predicts the damage bill from the severe weather to be millions of dollars more than the initial $5 million estimate.

Lord Mayor Ron Christie said teams have been surveying the damage.

"We had 10 teams out and about yesterday looking at roads, the rivulet and all our parklands and that costing now is well into the multi-million dollar," he said.

The council also sent teams to kunanyi/Mount Wellington to assess the damage.

"They went in a helicopter had a look around a mountain," he said.

"We couldn't get some of the trucks into the track areas because they're covered with debris."

Alderman Christie warned the public to avoid fast-running rivulets around the city.

"The rivulets are still unsafe, so mum and dad please keep the kids away from the rivulets," he said.

ABC