NSW’s Next Bushfire Crisis Might Be Its Contaminated Water Supplies

NSW’s Next Bushfire Crisis Might Be Its Contaminated Water Supplies
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The bushfire crisis is still continuing across NSW and Victoria but while the fires and the smoke pollution have been attracting the headlines, another issue could make the situation even more dire for affected parts including a major capital, Sydney. It’s our water supplies.

This article has been updated with WaterNSW’s latest response. It was originally published on December 19, 2019.

The fires across the state have been raging since September and have caused widespread devastation, including the deaths of 28 people and billions of wildlife as well as the destruction of more than 2000 homes. The fires, in NSW, Victoria and South Australia alone, have reportedly burnt more than six million hectares of land.

While the fire itself has inflicted a colossal amount of devastation, millions more have been affected by toxic air quality levels in major regions, like Sydney and Melbourne, as well as NSW’s South Coast and Victoria’s East Gippsland region. It’s caused the NSW and Victorian environment departments to issue alerts about the hazardous levels and for the states’ health departments to advise residents on how to limit exposure to the affected air, now considered the longest and most widespread in the state’s history.

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But the next environmental crisis anticipated from the persisting fires is its potentially devastating impact on water supplies.

During the worst of the bushfire days, videos emerged of NSW’s coastal beaches filled with ash sediment from the fires were posted on Sydney. But there are concerns that ash could also be in dams around the Sydney region, which will only worsen in the event of heavy rains.

Dr Jane Cawson, a bushfire expert at University of Melbourne, told Gizmodo Australia the threat will remain even after the fires are put out.

“[Sydney’s] dams may be affected if there is heavy rain after the bushfire. The fire area remains vulnerable to heavy rain for months or even years following the fire until the vegetation regenerates. Vegetation cover protects the soil surface from erosion,” Dr Cawson said.

“The likelihood that water quality will be affected in crucial water supplies [like Warragamba Dam in Sydney’s west or Cataract Dam] depends on the severity of the bushfire within the catchment area, the steepness of the terrain and whether or not there is heavy rain soon after the fire.”

Dr Ian Wright is a water pollution expert at Western Sydney University and he believes it might already be in the water.

“Warragamba has massive areas of burnt vegetation around it and I am certain this will cause a series of potentially major water quality problems,” Dr Wright told Gizmodo Australia.

“This will include sediment smothering stream, river and lake habitat and the nutrients possibly causing algal blooms. If algae growth takes off the lake can literally turn green. And algae can impart taste, odour and even water quality issues on water.

“If the rain is heavy and considerable, it could cause a mini surge of dark gray ink like water. This will be an unpleasant mix of ash (mostly dissolved) charcoal and partly burned leaves. I have seen it myself and sent water samples in for tests. It had sky high nitrogen and phosphorous.”

Cataract Dam, near Wollongong, similarly has areas of burnt vegetation nearby but is at just 25.5 per cent. It needs water but not heavy rains.

In response to the risk, the state government announced on January 15 it was fortifying the infrastructure around Warragamba Dam to “mitigate the inflow of ash to the system in the event of significant rainfall.”

“We have worked closely with the RFS to ensure fire retardant chemicals used near Warragamba Dam are appropriate, and that exclusion zones were in place to avoid the use of retardants in close proximity to water where possible,” Melinda Pavey, Minister for Water, Property and Housing, said.

“The NSW Government is also assisting local councils as the utility providers in areas affected by the recent fires by deploying resources to help with the management of their water supplies, including carting water where necessary.”

WaterNSW, who manage the water quality at the dams specifically, has confirmed it’s installed two booms in Warragamba Dam with silt curtains in order to catch any ash or contaminants flowing in the water. Another 1000 metres of silt curtains is on hand in case further reinforcments are needed in the Nepean or Tallowa Dams.

Back in December, WaterNSW confirmed it would use the following technology to ensure the water supply was not impacted by the rain:

  • The deployment of booms and curtains to intercept or isolate any inflows that pose a water quality risk to the storage.
  • Experienced water quality scientists using the highly sophisticated, real-time monitoring technology and models to predict where in the storage water quality may change. (Inspections confirm critical water monitoring instrumentation remains fully operational).
  • The capability to select water from various dams and from varying storage depths, ensuring that optimal quality water is supplied to Sydney Water and local councils for treatment.

But the water crisis is already happening in parts of NSW and it’s happened before in Canberra after fires ravaged areas near crucial water supplies in 2003.

“When water quality is impacted following a bushfire, affected communities may be advised to boil the water before drinking or an alternative (temporary) water supply may need to be arranged. Following the 2003 Canberra fires water quality from the Cotter catchment, which supplies Canberra, was severely impacted. As a result, a new water treatment facility had to be built costing $38 million,” Dr Cawson said.

In Tenterfield, near NSW’s northern border with Queensland, residents were advised on October 4 by NSW Health to boil water after its supplies were contaminated due to rain after the damaging bushfires.

“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.”

The boiling water alert for Tenterfield residents remains in effect until future notice. WaterNSW confirmed with us in December that there was no need for people living in the Sydney area to treat water at this stage.

“Our water storages are very low. So any pollution could be more concentrated and less diluted,” Dr Wright said. Warragamba Dam sits at around 43.6 per cent as stricter water restrictions were introduced in the region late last year.

“We need to watch Warragamba very carefully.”

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