Top End on track to break 80-year-old record after two wet seasons of low rainfall


Posted

April 24, 2020 07:23:08

Amid predictions that many parts of the continent will be getting some much-needed rain this winter, Australia’s Top End is experiencing its second bad wet season in a row, with some of the worst rainfalls since records began 80 years ago.

Key points:

  • Normal wet seasons provide around 1,600mm of rain, but this year it is looking to be more like 1,200mm
  • It is the second bad wet season in as many years for the Top End
  • The two years of poor rainfall are the worst on record since 1941, the BOM says

The Bureau of Meteorology (BOM) said it expected the western half of the Top End to get less than 1,200 millimetres of rain this wet season for the second year in a row.

Greg Browning, Tropical Climatologist at the bureau, said it was the first time this had been recorded since records began in 1941.

“It’s bad,” he said.

“You would expect 1,600mm in a normal wet season.

“To have two in a row is a pretty significant event.”

The wet season was disrupted by a positive Indian Ocean dipole, which meant it started later and was weaker than is normally the case.

“Essentially what the dipole means is that the monsoonal rains one can expect were weaker and got off to a slower start this year,” he said.

But Mr Browning said Australia’s southern states could see a 60 per cent chance of above-median rainfall for much of the country over the next several months.

The downpours could see large amounts of water dumped into the Darling River and other areas across the country’s south-east.

“It is not unexpected we are seeing a bounce back in the system in Australia’s southern states,” Mr Browning said.

“Often we see these sorts of recoveries and it’s likely there will be some great rainfall in some much-needed areas, like in New South Wales, this winter.”

Those rainfall predictions are in stark contrast to the northern parts of the NT, where there is now little meaningful rain predicted before the wet season officially finishes at the end of April.

Lacklustre wet seasons turn parts of dam into quagmire

At Fogg Dam Conservation Area, 70 kilometres south-east of Darwin, a muddy quagmire marks where a usually soaked water system should be.

The road across the dam is known for images of being covered in water amid the peaks of the wet season, and images of crocodiles waddling along flooded roads.

But in January, photos emerged on social media of the dam floor being exposed.

And now, while there is some water, the level is visibly low.

Pauline Cass, who helps run social media group Friends of Fogg Dam, said it was not normal to see it so low.

“It is sad to see the dam looking this dry,” she said.

“The dam should flood across the road to the point it is closed to traffic each wet season, but that hasn’t happened this year. It is a real concern.”

Mr Browning said ecosystems which relied on the “boom and bust” of monsoonal rains would come under increasing pressure if poor wet seasons persisted.

“From a climatologist perspective, if we have a lack of water recharge at the beginning of a dry season, then that system is drawing down on limited water resources. If that persists, then the climate will put greater stresses on those systems,” he said.

‘The rule book is being re-written’

The poor wet season comes after Australians around the country sweltered through a record-breaking hot and dry 2019.

Mr Browning says the “rule book is being re-written” when it comes to expected seasonal behaviours in Australia.

“We hope this is just an aberration but it’s very concerning seeing these patterns changing in areas that rely on the monsoonal rain patterns in northern Australia,” he said.

“Climate change is a factor which creates additional uncertainty in weather and it’s fair to say that last year has been full of those,” he said.

Mr Browning said the Top End could expect to see potentially worse fire seasons with drier vegetation if the pattern continued.

“With temperatures changing we are seeing more erratic weather behaviours, and this could include more erratic monsoonal seasons,” he said.

But there is a silver lining.

While overall this wet season has been relatively poor, some areas of the NT received heavy rainfalls

In January, a tropical low drenched some areas including the island of Dum In Mirrie south-west of Darwin, which received 562mm of rain in a 24-hour period.

And water users in Darwin can breathe a sigh of relief with the dam that supplies the city’s water now stable at 70 per cent capacity after falling to as low as 52 per cent earlier this year.

“We now have around 216 billion litres stored in the dam and, while there was some concern earlier this year, we feel we are in a robust position now,” said Trevor Durling, senior planning engineer at the NT’s Power and Water Corporation.

“We would need to look at serious water restrictions if we have another two successive years of poor wet seasons though,” Mr Durling said.

Topics:

weather,

rainfall,

community-and-society,

environment,

darwin-0800,

nt,

qld,

australia





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