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How can bushfires impact water supply and delivery?

Bushfires have destroyed more than 400 homes in New South Wales (NSW) in the past fortnight, while in Queensland more than 70 fires are still burning across the state.

Communities in Western Australia are also on alert, with catastrophic conditions forecast on Sunday in four regions of the state: east Pilbara coast, west Pilbara coast, east Pilbara Inland and Ashburton Inland.

Along with the devastating loss of life and property damage, high-intensity fires can also impact water catchments and impinge on water supply and delivery.

For water utilities, it is important to be prepared for both the short-term impacts and longer-term concerns, said University of New South Wales Professor of Civil and Environmental Engineering Stuart Khan. 

“These are things we need to be very aware of in the coming months,” Khan said.

“Immediately, the real risks are that you might lose the ability to treat and pump water.”

This was a reality faced by the NSW Northern Rivers city of Grafton last week, when bushfires interrupted power supply to Shannon Creek dam. 

Located 18 km south of Grafton, the off-river storage reservoir supplies water to the Clarence Valley and Coffs Harbour regions. 

The power issues caused the water pump to keep tripping out, while the fire meant Clarence Valley Council (CVC) staff were unable to get to the site and connect the backup generator. As a result, CVC had to immediately introduce Level 4 water restrictions to conserve water already in the system.

"This is a major potential concern when we face fires close to a town,” Khan said.

“We can lose access to water supplies because of pumping or pipeline failures.”

Luckily for Grafton, Clarence Valley and Coffs Harbour share the Regional Water Supply Scheme, which allows bulk water to be transferred between the two. This meant the water restrictions could be lifted six days after power supply was first interrupted.

“In a great example of cooperation, the councils built a water sharing system that provides flexibility and means if one system gets into trouble it can draw from the other – as happened recently,” Khan said.

Queensland's Toowoomba Regional Council (TRC) is also feeling the impact of fire on its water supply infrastructure.

TRC today urged residents to limit their water consumption to domestic use, after fire damaged powerlines connected to the Cressbrook dam pump station, which means water cannot be pumped from the dam to Toowoomba and surrounding towns.

Khan said towns that are able to draw from more than one major water reserve will be better able to cope with extreme weather events. 

“Diversification of water sources has been shown to be a really useful strategy,” Khan said.

“For example, when there was major flooding in Brisbane, the city almost ran out of water because it couldn’t treat it quickly enough. It was able to draw water from the Gold Coast desalination plant as a backup.”

Long-term catchment concerns

Queensland Fire and Emergency Services (QFES) Acting Commissioner Mike Wassing today said it would take heavy rainfall to help get the 70-odd blazes in the state under control.

While rain would provide welcome assistance to the firefighters, a large downpour can make water treatment difficult for utilities with bushfire-affected catchments.

“With some bushfires, there might be very little impact to waterways until the next big rainfall event,” Khan said.

“Fires leave a lot of burnt biomass sitting on the forest floor, which tends to be rich in organic carbon and phosphorous. 

“A high nutrient load like this, which under summer conditions is likely to produce algal blooms, can make treating water difficult and lead to taste and odour problems.”

This was seen following the fires that burnt across NSW and the ACT from December 2001 until mid-January 2002. Caused by multiple lightning strikes and exacerbated by preceding months of hot, dry conditions, the fires spread rapidly and burnt 25,000 square km of forest in the Blue Mountains.

When rain fell in January, ash and sediment from the fire washed into waterways. Studies of the water found increased levels of total suspended solids, and increased concentrations of total phosphorus and nitrogen following the fires compared to average pre-fire values.

Although there is no simple solution to preventing biomass ending up in catchments, Khan said it helps to have appropriate strategies in place. 

Planning and preparedness

In a paper developed by Water Research Australia, Khan and research colleagues from academia and industry outlined the consequences of extreme weather events on water quality and how to manage these.

Mitigation strategies included enacting incident response plans and ensuring effective communication between water utilities, health authorities and other relevant organisations. 

“Having these strategies and protocols in place ahead of time is a key part of being able to respond quickly and effectively,” Khan said.

Following an extreme event, he said it was useful for utilities to review the plans they had in place and learn from the experience. With the Intergovernmental Panel on Climate Change (IPCC) reporting that it is very likely that heat waves will occur more often and last longer, and that extreme rain events will become more intense and frequent in many regions, it is possible the Australian water sector will be dealing with events like bushfires more often.

And Khan said the sector is already quite well prepared.

“The water industry in Australia as a whole has taken significant steps to get ready for these types of events,” he said.

“It’s good news that the sector has done a lot of groundwork and has started to prepare for what might be coming."

There are a number of groups collecting donations to help those affected by the bushfires, including:

If you need support, please contact Lifeline on 13 11 14 or Beyond Blue on 1300 224 636.