There’s been some pretty impressive totals — Wilcannia has recorded more than 70mm, Burrawantie homestead near Bourke (59mm), and Cunnamulla (47mm) — with more forecast today.
But while the rain is the latest in a soggy start to 2019 for western Queensland, Paul Lainio, a hydro-meteorologist (water and weather expert) at the Bureau of Meteorology, said there was mixed news on where all the water was flowing and what it meant for the drought.
In late January and early February there was the now-infamous low-pressure system in an active monsoon trough that settled across northern Queensland.
“That was a period where we saw really, really significant floods in Townsville and also through the Flinders River; massive rainfall through that very far northern area,” Mr Lainio said.
This rain was devastating in terms of property damage and large stock losses, however it brought relief for some people downstream.
“We had some very good falls extend into the north of the Diamantina River catchment, and that’s one of the rivers that flows down towards South Australia and eventually turns into the Warburton River and flows into Lake Eyre.”
That hasn’t been all.
“That rainfall was then followed during March, with ex-Tropical Cyclone Trevor moving through the Northern Territory and then across south-west Queensland,” he said.
“That produced very large falls through the catchment of the Georgina River and Eyre Creek and into the Diamantina and the Cooper as well, with a little bit of rainfall also heading into the Paroo and Bulloo river catchments.”
Thankfully this rainfall from Trevor’s remnants was less devastating, Mr Lainio said.
“It was more good news for farmers who rely on that floodplain to fill up occasionally and to really produce good conditions for grazing.”
Lake Eyre set to be its fullest since 1974
It’s already looking good and it’s about to get better.
Mr Lainio said the rain over recent days probably would not have a significant impact on Lake Eyre, but things were already in swing thanks to the combination of those aforementioned big rainfall events.
Thanks to the monsoonal rain, the lake was probably around half-full at the moment, he said.
So the next question is how much more will Trevor add?
“There’s not much more inflow happening now. We’ll need to wait, say, a month to six weeks before we see further inflows reaching Lake Eyre.
“In this case, we don’t believe the Thompson-Barcoo has enough flow to reach Lake Eyre. It will fill a place called the Coongie Lakes.”
The Diamantina River wasn’t flowing as much as it did the first time around either, Mr Lainio added, but Eyre Creek was showing promise.
“The Eyre Creek system is in a big, big flood this time around,” he said.
“It’s wending its way towards South Australia, moving through some very dry land, so a lot of that will be absorbed on its way to Lake Eyre, but we still believe some will make it.
“We think around three-quarters full might be where the lake ends up in June.
“Then given the large amount of water accumulated in Lake Eyre, we think it will still be around right through winter and well into spring.”
Three-quarters full! That would definitely make this year one for the record books.
Mr Lainio said the last big flood year for Lake Eyre was in 2010 when it was around a third full.
“Certainly, it’s fuller than we saw in 2010 already. It may be that what we’re seeing, with these two events contributing to the inflows, is the fullest lake since 1974.
“1974 was a very wet year indeed and the lake was considered to be full — so this event may be the fullest since then. It is certainly a very significant event.”
The Darling and the drought
The Lake Eyre Basin may have been getting a drenching, but sadly the Murray-Darling has largely missed out.
Mr Lainio reiterated that while the Bureau of Meteorology didn’t officially declare droughts, it kept an eye on rainfall deficiencies. For parts of western Queensland, it is looking good.
“Certainly, some of the longer-term rainfall deficiencies through western and northern Queensland, they’ve largely been reduced,” he said.
“But as far as parts of southern and south-eastern Queensland and adjacent New South Wales, they’re still really quite dry.
“We may have had this recent event through the area, but that really hasn’t had a big effect on the longer-term rainfall deficiencies, so there’s still a bit of work to be done through there.”
When it comes to the river itself, things aren’t much better.
“It looks like the Darling might get a little bit of flow, but the region is very, very dry, so a lot of the flow will be eaten up by billabongs and braided channels and dry land,” Mr Lainio said.
What would it take to get the Darling going again?
Well, a lot. A lot. A lot.
Mr Lainio said it would take an event similar to the one we saw with the monsoon low — hundreds of millimetres over a very short period of time — or a series of significant falls.
“In this event we’re only looking at falls in the order over 100mm. When we look at the rainfall maps that we saw through Queensland in the past three months, they were looking at upwards of 400mm to 1,500mm of rainfall — a much different scale.
“You’d certainly need more rain through the Murray-Darling Basin catchment to really see those river systems get some good inflows through there.”
Source: ABC News 2019-04