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Should we fear a post-bushfire water quality crisis?

By Charles Essery - posted Wednesday, 8 January 2020

Already, the usual pundits are queuing up to spruik the next crisis/catastrophe from the 'world news' NSW and Victoria bushfires (Fairfax Press, The Guardian, UK Daily Mail, The Independent, etc). The bushfires will indeed alter the landscape of catchments and as a result increase erosion (due to lack of ground cover) and the subsequent inflow of sediment and ash into the rivers and dams/storages that are the main source of our drinking water supplies. The only sources that will not be immediately impacted will of course be groundwater and desalination plants. For those who like, operate and promote desalination plants, it's good news for business and their shareholders.

However, those in the water industry who manage catchments and operate treatment plants have dealt with this issue regularly. The water industry has previously monitored the impact before and after similar events and, as a consequence, has developed procedures and processes that mitigate the immediate impacts on water quality. The firefighting authorities and volunteers are to be commended for their protection of vital water assets (pump stations, treatment plants etc). This is one on the most important pre-emptive activities for forthcoming weeks/months for all of us who drink tap water.

The industry is also experienced in managing the longer-term impacts that result from the settling of sediments on the storage floors, which can influence water quality (particularly nutrient levels) for several years. In the case of river-sourced water, there is little choice other than to enhance treatment processes and increase operating costs. Those with large storages or multiple storages, can selectively extract water to avoid the poor-quality water that can result from the initial rains after the fires.


Unlike other impacts from the bushfires, water quality can be regularly monitored and reviewed by health departments and any water authority would be brought to task should they fail to manage the impacts of bushfire-related changes. Numerous studies here and abroad have studied the impact of bushfires and the water industry has established monitoring programs and treatment process adjustments to offset the impacts of pollution events which usually occur with subsequent rainfall events.

Well-managed forested catchments supply water to the likes of Sydney and Melbourne, and partially so in many other storages across Australia. Around the world, they are an ideal land use type for producing good quality water and indeed, in Sydney's case, produced drinking water without the requirement for treatment plants until 1995.

When forested catchments burn, the obvious impact is ash and then erosion of the bare surfaces. The immediate water quality impacts come from the subsequent rainfalls which produce runoff with a high load of ash, sediments and nutrients (particularly nitrogen and phosphorous) which initially put high demands on the treatment plants. Fires also have longer term impacts on the hydrological character of the catchments, hindering the infiltration of water into the soil. Such impacts and the settling of sediments in storages can enhance the chance of algal blooms which require significant management (and expenditure) by the water utilities.

The large metropolitan and regional water utilities usually have the capacity and resources to manage these impacts. Regional utilities will have safeguarded their key assets with the significant help of the fire authorities. The real strain will occur with the many small rural towns which have less income and fewer resources. Many of these small towns take water direct from rivers and small storages and do not have treatment plants. Chlorination usually occurs which controls microbiological contamination, but this has no effect on chemical contamination, water may have significant taste/odour issues when contaminated by ash or other sources e.g. road spills etc. The smaller utilities must rely on their own skill/judgment and advice from government department expertise and, as such, water quality may temporarily reduce in terms of attributes like odour and taste but should be able to maintain the more critical health standards.

One of the most contentious issues raised is the long-term impact of algal blooms in storages, which if not managed, can cause significant quality problems. However, while bushfires can enhance the likelihood of blooms, algal blooms are common in hot climates like Australia, and are affected by many factors. As such, water utilities have significant experience and capacity in dealing with these and will have monitoring and procedures in place to ensure water quality is maintained for their customers.

Water quality from natural and polluted catchments is the operating environment that water utilities are used to dealing with on a 24/7/365 basis. Sometimes mistakes do happen, and extreme events can occur (e.g. the 1998 Cryptosporidium event in Sydney) and water quality may reduce due to operational constraints. However, having worked within the industry and later as a regulator, I have seen the capacity of professional operational staff to deal with the effects of these bushfires on water quality. The only caveat I would add, as a cautionary note, is that my confidence would wain, should politicians, spin-doctors and climate change activists try to interfere with these water professionals in the fulfilment of their duties. I foresee that climate change cultists will add this to their list of catastrophes caused by C02 emissions. They will inevitably want to spruik this as just another burden that they can dump on the backs of those who dare to challenge their beliefs.


So while some media outlets have started warning of a water quality crisis, I would suggest that the professionals be allowed to manage the issue (as they have done before). This is not to say that we don't need to hold the water industry to account. Regulators must ensure that they maintain their monitoring and control of the catchments and storages. But we don't need panic merchants with vested interests trying to push us into fearing yet another "mega issue". In the words of that seminal twentieth century satirical work the "Hitchhikers Guide to the Galaxy",… DON'T PANIC!

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About the Author

Charles Essery is an independent water consultant, who has been an Australia resident since 1990.

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