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Designing tools to predict and mitigate impacts on water quality following the Australian 2019/2020 wildfires: insights from Sydney's largest water supply catchment / Jonay Neris Tome; Cristina Santin Nuno; Roger Lew; Peter R. Robichaud; William J. Elliot; Sarah A. Lewis; Gary Sheridan; Ann‐Marie Rohlfs; Quinn Ollivier; Lorena Oliveira; Stefan Doerr
Integrated Environmental Assessment and Management
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The 2019/20 Australian bushfires (or wildfires) burned the largest forested area in Australia's recorded history, with major socio‐economic and environmental consequences. Among the largest fires was the 280,000 ha Green Wattle Creek Fire which burned large forested areas of the Warragamba catc...
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The 2019/20 Australian bushfires (or wildfires) burned the largest forested area in Australia's recorded history, with major socio‐economic and environmental consequences. Among the largest fires was the 280,000 ha Green Wattle Creek Fire which burned large forested areas of the Warragamba catchment. This protected catchment provides critical ecosystem services for Lake Burragorang, one of Australia's largest urban supply reservoirs delivering ~85 % of the water used in Greater Sydney. WaterNSW is the utility responsible for managing water quality in Lake Burragorang. Its postfire risk assessment, carried out in collaboration with researchers in Australia, the UK and USA, involved i) identifying pyrogenic contaminants in ash and soil; ii) quantifying ash loads and contaminant concentrations across the burned area; and iii) estimating the probability and quantity of soil, ash and associated contaminants entrainment for different rainfall scenarios. The work included refining the capabilities of the new WEPPcloud‐WATAR‐AU model (Water Erosion Prediction Project cloud‐Wildfire Ash Transport And Risk‐Australia) for predicting sediment, ash and contaminants transport, aided by outcomes from previous collaborative post‐fire research in the catchment. Approximately two weeks after the Green Wattle Creek Fire was contained, an extreme rainfall event (~276 mm in 72 h), caused extensive ash and sediment delivery into the reservoir. The risk assessment informed on‐ground monitoring and operational mitigation measures (deployment of debris‐catching booms and adjustment of the water supply system configuration), ensuring the continuity of safe water supply to Sydney. WEPPcloud‐WATAR‐AU outputs can prioritize recovery interventions for managing water quality risks by quantifying contaminants on the hillslopes, anticipating water contamination risk, and identifying areas with high susceptibility to ash and sediment transport. This collaborative interaction among scientists and water managers, aimed also at refining model capabilities and outputs to meet managers’ needs, exemplifies the successful outcomes that can be achieved at the interface of industry and science.
drinking water, bushfire, wildfire ash, water contamination risk modeling
College of Science