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Jarrah trees dying in WA's big dry

Anthony Sharwood, Thursday April 11, 2024 - 10:30 AEST

This is the image that sums up the ongoing desperately dry spell in the southwest corner of Western Australia.

The scene shows bushland at Morangup in the Perth Hills, about an hour or 70 km northeast of the Perth CBD. The property is owned by engineer James Holbeach, who says he's had just 3 mm in the last 150 days. That all came on one day, on January 24. The previous day of rain was November 12.

In the image, the smallish red tree on the left of the picture is a relative young Jarrah tree that just died from lack of water. Holbeach says many trees are dying.

"A lot of old growth trees seem to be doing OK but here and there, single trees are dying. You'll see this sea of green and then a splodge of brown where a tree has died due to lack of water.

"At the end of winter, this scene was very green and carpeted in wildflowers."

As you'd expect, water tanks are running low across the region. Holbeach's tank holds 120,000 litres, which is equivalent to about two swimming pools. Right now it’s down to 15% capacity. Holbeach has had to buy water in previous dry summers and the water tanker has always arrived the next day. When he called the water guy recently, demand was so high that he took almost two-and-a-half weeks to arrive.

The water table is dropping too, Holbeach says. The water level in his bore is normally 25 metres below the surface but has dropped to 30 m, the first time he’s seen it that low.

Here at Weatherzone, we’ve written several recent stories about the southwest WA dry spell, beginning with the article that revealed Perth experienced its driest six-month period in 148 years of records.

Source: BoM.

The chart above shows the 6-monthly rainfall deciles for Australia from Oct 2023 to March 2024. As the dark red shows, the area around Perth was the driest on record.

And April has brought no relief to date. The chart below shows rainfall totals, as in the raw numbers rather than the percentage of the average. Bottom line: still nothing in the southwest.

Source: BoM.

Sadly, there is no break in the pattern in the foreseeable future with warm, dry weather expected in Perth for at least the next week as yet another slow-moving high pressure system centred south of the continent blocks the northward progression of rain-bearing cold fronts.

Compounding the frustration for residents of southwest WA is the heavy rain fed by tropical moisture which has drenched normally bone dry areas like the Nullarbor but generally steered clear of the southern portion of the west coast.

Again this week, there’s an active tropical system though sadly, the remnants of ex-Tropical Cyclone Olga along with a low in the upper atmosphere could deliver significant falls of rain to large parts of the state while likely bypassing Perth and surrounds.

"There’s genuinely a feeling like we live under some sort of dome here," Holbeach says.

The imaginary rain-proof dome will of course be penetrated at some point as late autumn, winter, and early spring are the region's wettest months, though even the first rain won't be instant good news. For one thing, the ground is "hydrophobic", meaning it’s been baked so hard by a combination of clear skies and searing hot temperatures that the first rain won't soak in.

Meanwhile as farmers do it tough – with wheat growers prevented from burning stubble due to the ongoing fire risk – and with ecologists warning of a potential forest collapse on a massive scale, all southwest WA locals can do is wait, and hope.

"Everybody’s waiting for rain," Holbeach says. "It's been an exceptionally hot summer and everybody is just desperate for rain, and we need a lot, too.

"The Perth weather forecast is just ridiculous. Even in April, every day it’s 30 degrees with no rain."

- Weatherzone

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More rain for thirsty southwest WA

16:46 AEST It won't be a deluge, but at least some rain is heading the way of the parched southwest corner of Western Australia from Friday into the weekend.