MARGARET River, Cowaramup, Forest Grove and Cape Naturaliste were among 65 locations across the south west of the state to receive record low rainfalls last month.
The Bureau of Meteorology monthly climate summary for July blamed “persistent high pressure systems over southern WA during the month and a contraction of the usual fronts and westerly winds southwards” for the low rainfall.
Averaged across the Lower Southwest - south west of a line from Jurien Bay to Bremer Bay - last month was the driest July since comparable records started in 1900, and also the seventh warmest on record.
But while days were relatively warm and dry, nights were colder than usual with overnight temperatures well below average because of clear skies and light winds.
According to BOM, Margaret River’s total rainfall for July was 80.4mm, only 37 per cent of its July average over the past 84 years of 215.7mm. It was also significantly drier than the previous driest July, in 2001 when 93mm was recorded.
At Forest Grove 88mm fell, 39 per cent of its 222.2mm July average, while the previous driest July was 1971 with 90.3mm.
Cowaramup’s rainfall was 91.8mm, 41 per cent of its 222.1mm July average. The previous driest July was also 2001, with 94.6mm.
At Cape Naturaliste only 49.8mm of rain was recorded, just 30 per cent of the average 161.2mm for July and almost 18mm less than 2001, the previous driest July.
BOM pointed out the driest July across the Lower Southwest followed a near-average-rainfall June and the seventh driest autumn on record.
Low run-off and groundwater recharge rates since autumn had Margaret River’s water supply, the Ten Mile Brook Dam, at 33.75 per cent of capacity with 571 megalitres on July 31 before welcome rains on the first three days of this month.
In May Ten Mile Brook Dam recorded its lowest level of 381ml, or 22.53 per cent of capacity, since 2002.
Despite Witchcliffe topping the state’s rainfall today, Friday, with 36.6mm in the 24 hours to 9am, BOM meteorologist Patrick Ward warned there is only a 50 per cent chance of significant spring rains to replenish South West dams, rivers and ground water systems quickly.
“The chances of the August-October period being drier or wetter than normal is roughly even, there are no real drivers in the climate system at the moment so there’s no real indication of what rain is coming,” Mr Ward said.
Warming Pacific Ocean currents also meant Australia was “pretty close” to an El Nino climate event and while the impact would be less in WA, he said “with an El Nino I wouldn’t expect it to be very wet”.
Margaret River Wine Industry Association chief executive officer Nick Power said the region’s grape growers had “noted” the dry July.
“We can’t change the weather, we will just have to take what we’re given,” he said.