How Rain Affects Australia’s Bushfire Smoke Pollution

How Rain Affects Australia’s Bushfire Smoke Pollution
Image: Getty Images


Parts of NSW, including Sydney, have received a long-awaited deluge of rainfall over the past day. While some concerns have been expressed over whether it might push bushfire ash contaminants into the state’s water supplies, the rain’s impact on the region’s air quality might be alleviating some other worries for those affected.

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While the bushfires themselves have been devastating, it’s the lingering smoky conditions that have continued to affect millions of Australians around the country’s fire-affected regions. Northern NSW’s fires near Port Macquarie made air quality hazardous back in October while two megafires, the Gospers Mountain and Green Wattle Creek fires, near Sydney choked the city of millions for weeks on end.

In December 2019, catastrophic fire conditions started blazes that ripped through millions of hectares of land causing further unprecedented levels of hazardous air quality through NSW’s south coast and Victoria’s East Gippsland region. Images from affected towns in the area, like Mallacoota and Cobargo, showed bright red and orange skies, reminiscent of apocalyptic movies rather than the real world — the red tinge enough to indicate extremely dangerous air.

The fires have begun to be contained with more favourable conditions in recent weeks. However, the poor air quality in major cities such as Melbourne and Sydney remains an issue, interrupting major sporting events like the Australian Open.

Thankfully, the Department of Planning, Industry and Environment (DPIE) has confirmed to Gizmodo Australia the rain being experienced across parts of NSW is helping to alleviate the state’s bad run of bushfire smoke pollution.

“Rain plays an integral role in reducing air pollution — washing the pollution from the atmosphere,” a spokesperson at DPIE told us.

“Rain washes particulate matter out of the air, however, the improvement in air quality is dependent on the amount of rainfall and the amount of air pollution.”

While the rain has been quite heavy across Sydney, the smoke hasn’t completely subsided and the department explains it will continue until the bushfires are put out.

“Air quality has improved across much of NSW, including Sydney. However, there is still significant amounts of smoke in the environment,” the department’s spokesperson said.

“Until the fires are extinguished smoke may continue to affect communities both close to the fire and further afield.”

We’ve also reached out to Victoria’s Environmental Protection Authority but it did not respond in time for publication.

While the dangerous particulate matter (PM) causing poor air quality is washed out of the air, it instead falls to the ground, causing issues for key water supplies when ash-riddled soil and sediments is pushed into waterways by the heavy rain.

“At this time, the washout of smoke and air particles is not expected to affect water quality in NSW,” the DPIE added.

Water quality has already been affected in other parts of the state, however. Tenterfield, near the Queensland border, were told to boil water after its water supplies were contaminated due to heavy rain following the bushfires. Residents were advised of the boil water alert on October 4 by NSW Health and it was lifted after two months on December 23.

“Recent conditions for fires at the Tenterfield water supply dam have caused problems with water treatment, making drinking water in the Tenterfield Town unsafe,” the alert read.

“Water used for drinking or food preparation should be brought to a rolling boil to make it safe.”

Gizmodo Australia has reached out to Sydney Water to confirm whether the city’s water quality remains the same despite the heavy rain in catchment areas.

“Sydney Water and WaterNSW are closely monitoring the situation and have response protocols in place to manage inflow events,” a Sydney Water spokesperson told us.

“Sydney Water adjusts its treatment processes to suit the quality of raw water being supplied from the dams.

“The residents of Sydney, the Blue Mountains and the Illawarra can be assured their water is high-quality and meets the Australian Drinking Water Guidelines — which are some of the strictest in the world.”

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