The Impact of Bushfire Events on Drinking Water Catchments
In 2019, the bushfire season in Queensland started much earlier than expected. After months of fires in areas including the Gold Coast Hinterland and Sunshine Coast, bushfires in NSW and Victoria swelled destroying entire towns on New Year’s Eve. Bureau of Meteorology forecasted that January to March 2020 could have had an equal chance of being wetter or drier than average, though thankfully, the former prevailed. Downpours in February extinguished or assisted firefighting efforts to get blazes under control, including the Lindfield Park Road fire.
NSW’s longest running fire, the Lindfield fire near Port Macquarie Airport, started on 18 July 2019 and ended on the 13 February 2020 (that’s 210 days). In September 2019 the rural fire service tried to tackle the fire by flooding it with reclaimed water. Rural Fire Service district officer Stuart Robb said “The rehydration was a key component to the fire being extinguished. We have had 65 megalitres of water flow into the wetland, which brought the water levels up to a point where the surface water from the recent rains has been able to complete the extinguishing."
But what about the impact on drinking water catchments after the fire?
The ADWG states that contamination events are often associated with extreme events. Bushfires, natural disasters and sabotage are examples of hazardous events that need to be considered in risk assessments and the management of incident and emergencies. It is a requirement to develop appropriate protocols which involves a review of the hazards and events that can lead to emergency situations, including bushfires.
The Australian Water Association, in partnership with the UNSW Global Water Institute, the NSW Water Directorate and the Water Services Association of Australia held a workshop on Monday 3rd February 2020 on drinking water quality management in bushfire affected catchments. Many water organisations shared their experience with the ongoing bushfires and drought conditions impacting the supply of water. A number of elements raised could be considered in drinking water risk assessments, completed as part of incident and emergency preparedness, or used in the recovery phase after extreme events.
Mangrove Creek Dam bushfire 2019 (Shane Geerin, NSW RFS)
Every fire is different and the burn extent, burn intensity/severity, vegetation cover/type and erosion potential are all important factors to consider. Preparation work can be completed by water utilities prior to a bushfire event in a drinking water catchment e.g. mapping erosion potential, listing critical infrastructure. Having this work completed prior to a bushfire can assist during an event (e.g. information can be provided to emergency services) and can reduce the recovery timeframes.
Water quality risks – What you need to do.
Viridis can assist with risk assessments and planning work prior to a bushfire event. Decreased dissolved oxygen, increases in organic loads and suspended solids in source water, THMs, and metals including leads all need to be considered. Post bushfire there is an increased risk of algal blooms, cyanotoxins and taste and odour issues. Assessment need to consider the risks that come from higher intensity fires versus low intensity and the risks posed by the use of fire retardants.
Viridis can assist with risk mitigation strategies including what mapping and information should be ready to go, and who may require it. The Queensland Fire and Emergency services have the power to take water under the Fire and Emergency Services Act 1990. Can your recycled water be used in a fire? What approvals do you require?
We also can help with recovery planning including what operational monitoring should occur post fire and what observational monitoring maybe required in your catchment. Remember access into the catchment may not be possible for a considerable time after an event. Your drinking water infrastructure maybe physically damaged or fire related power outages may cause a loss of drinkable tap water. Can your filters handle the increased sediment loads? The catchment may take a considerable amount of time to recover before it produces the same yields prior to a fire.
With changes occurring due to climate change, and mean temperatures steadily increasing, catchments are drier than before. Extreme events are becoming more frequent and more intense. The best thing you can do is to start planning and preparing for bushfires in your drinking water catchment now.