As the threat of catastrophic bushfires eases across some parts of Australia, attention is now turning to their long-term impacts on essential services such as drinking water.
Bushfires are still burning across large parts of Australia, but some scattered showers over the past week brought welcome relief for communities trying to extinguish the blazes. However as talks of recovery efforts continue, attention is now turning to how the fires are impacting drinking water supplies.
According to Stuart Khan, a professor of civil and environmental engineering at University of New South Wales (UNSW), bushfires affect water quality from source to tap, and effects can vary between the short and long term.
Power outages, fire damage and demand from firefighting efforts mean some water treatment facilities can’t keep up with demand. This can cause untreated water to be fed directly into drinking water systems, something that has already happened in several communities in fire-affected areas.
Bushfires have badly damaged water treatment infrastructure in several states, leading to boil-water alerts and pleas to conserve water for only essential use.
SA Water has asked Kangaroo Island residents and visitors to conserve water after its Middle River Water Treatment Plant and pumping operations were badly damaged by fires there last week.
And in Victoria, a new service has been set up with the aim of giving residents a point-of-contact for information about water quality in the state. South East Water, on behalf of the Victorian water industry, will coordinate water relief for affected areas.
“We want to make sure those affected by the bushfire have practical support when it comes to drinking water,” said Minister for Water Lisa Neville.
Rain, rain, go away?
It sounds counter-intuitive, but rain can also cause water quality problems for fire-affected areas. While it helps replenish water supplies, it can also wash materials such as ash, eroded soils, fire retardants and debris into storage areas and waterways.
This can severely impact drinking water supplies by affecting everything from the taste to stimulating the growth of blue-green algae and damaging filtration systems.
Communities throughout bushfire-affected areas have been issued warnings about water quality, with some encouraged to boil water before use for drinking, food preparation and hygiene purposes. Residents are also relying on bottled water or water imported from surrounding networks, especially if there is concern that chemicals from retardants have entered water systems.
The water industry is already mobilising to help mitigate some of this damage. NSW Minister for Water, Property and Housing Melinda Pavey said that as the fire risk to the Warragamba precinct eases, WaterNSW and Sydney Water are focusing on protection measures for drinking water supplies.
This includes floating containment booms and curtains, extensive use of monitoring technology to predict how water quality might change over time, and selecting water from various dams and varying storage depths to better maintain optimal quality.
Khan said time will tell if there is long-term damage to drinking water quality depending on how bushfires impact catchments.
“Drinking water catchments are typically forested areas, and so are vulnerable to bushfire damage,” he said.
“Impacts to bushfires and subsequent erosion can have long-lasting effects, potentially worsening untreated drinking water quality for many years, even decades.
“Following these bushfires, many water treatment plant operators and catchment managers will need to adapt to changed conditions and brace for more extreme events in the future.”
Australian Water Association President Carmel Krogh expressed support for communities and individuals affected by bushfires, and said this is a time for Australia’s water industry to take stock and focus on recovery.
“Now and over the coming months, we as an industry will have our work cut out for us as we attempt to manage the effects of the bushfires on catchments, drinking water quality and water demand,” Krogh said in a statement.
“The fires, combined with the ongoing drought, are a challenge for all of us and never have we needed more collaboration across so many areas.
“In the meantime, we urge everyone to lead and share the message of water conservation to help manage our precious water supplies during these challenging times.”
Larger forces at play
Although the fire risk might be easing in some areas and rainfall over the past few days is welcome weather, the threat hasn’t passed. Bushfire season still has several weeks to go, and it’s possible that this year foreshadows a trend towards more extreme seasons in the future.
New data from the Bureau of Meteorology (BOM) paints 2019 as the warmest and driest year on record. The Annual Climate Statement 2019, released late last week, shows the average mean temperature in 2019 was 1.52ºC above average – the highest since records began in 1910. National average rainfall levels were also at a record-setting low of 277 mm, the lowest since records began in 1900.
These warm and dry conditions contributed significantly to the current fires burning across the country, said BOM Head of Climate Monitoring Dr Karl Braganza.
Causes for these extreme weather conditions include a very strong positive Indian Ocean Dipole (IOD), which brought warm and dry conditions to much of Australia’s landscape from about the middle of last year. IODs are caused by sustained changes in the difference between sea surface temperatures in the eastern and western Indian Ocean. A positive IOD means less moisture than normal in the atmosphere to the northwest of Australia, often resulting in higher than normal temperatures during winter and spring.
Another significant contributor to this hot and dry year was a “rare” Sudden Stratospheric Warming event above the South Pole, which Braganza said compounded the warmer and drier conditions over southern Queensland and New South Wales.
He added that on the whole, Australia’s climate has warmed over the decades since the BOM started keeping records, which means conditions that contribute to more extreme bushfire seasons are likely to continue.
“Australia’s climate has warmed by more than a degree since 1910, which means warm years like 2019 are now more likely to occur, while the trend in recent decades has been for drier winter and spring seasons in the south,” he said.
Rainfall in the coming months is also predicted to be at or below average for the east coast, while temperatures are likely to remain high for the rest of the summer.
“Unfortunately the outlook is not indicating a widespread return to wetter than average conditions over drought and fire affected parts of eastern Australia,” Braganza said.
“It’s important the community remains vigilant to the risk of more heat and fire days this summer, particularly given how dry the country has been over the past 12 months.”