Science-backed tools enhance water catchment management

Heavy rain in areas burnt by bushfire can mobilise massive volumes of sediments and nutrients into rivers and water reservoirs, threatening the quality and supply of water to Australia’s capital and regional cities and damaging freshwater ecosystems.

The latest AFAC case study explores how researchers with the former Bushfire CRC are now working with ACT Parks and Conservation Service (ACT PCS) and AFAC's Rural and Land Management (RLM) Group. The partnership has developed an innovative suite of tools and resources to help end-users identify water catchments susceptible to post-fire soil erosion, flooding and water quality risks.

ACT PCS managed and trialled the suite of tools successfully in 2015/16 and now uses the resources to plan prescribed burning operations and also target drainage and infrastructure works in identified risk- prone areas with significant water assets and important ecosystems.

Dr Petter Nyman and colleague Dr Gary Sheridan of the University of Melbourne drew on their research with the Bushfire CRC’s Fire in the landscape project and their former work with the Victorian Bushfire Rapid Risk Assessment Team (Bushfire RRAT) to develop the evidence-based tool kit. They investigated the link between factors such as fire severity, rainfall intensity and post-fire debris flow processes. This included site-specific studies in north eastern Victoria.

“Burned headwaters catchments contain large amounts of ash, sediment and debris that can be flushed into rivers and water supply reservoirs. High sediment loads from debris flows cause high turbidity and water contamination due to increased nutrient and metals from pollutants in the runoff,” according to Dr Nyman.

This type of contamination occurred from post-fire debris flows after the Canberra fires in 2003, resulting in water restrictions to the ACT until a new water treatment plant was constructed.

“We also saw this type of contamination in the Ovens River after the Eastern Victorian alpine bushfires in 2003 due to sediment and nutrient from debris flows in burned headwaters,” says Dr Nyman.

“Debris flows also led to contamination of Lake Glenmaggie after the 2007 bushfires in Victoria. The impacts of burned catchment on water quality were also documented elsewhere in south east Australia, including the Nattai Catchments near Sydney and the Lofty Ranges near Adelaide, although we have not yet observed the extreme type of debris flow processes in these areas.

“These scenarios from various landscapes across south eastern Australia highlight the importance of considering water quality issues when managing fire in high value water-supply catchments,” he says.

The researchers worked directly with ACT PCS, as the lead end-user agency and in collaboration with AFAC’s Research Utilisation Manager, Dr Noreen Krusel, and the RLM group to develop and implement utilisation of their CRC research.

Their collaboration delivered two key outputs for utilisation. The initial output funded by AFAC in 2014, was an Australia-wide assessment of post-fire erosion risk accompanied by generic guidelines for evaluating risk to water quality. This was followed by the development of a suite of GIS tools, funded, managed and successfully trialed by ACT PCS in 2016. The tools generate post-fire risk assessments of erosion, flooding and water quality and build on other collaborative work by the researchers for the Bushfire RRATs in Victoria.

ACT PCS lead end-user Dr Adam Leavesley says the work has changed the way the agency identifies and manages the potential impact of post-fire erosion.

“The tools have enabled us to integrate water quality risk into our burn planning and implementation, plus they have given us the capacity to assess the risk after planned and unplanned fires,” he said.

The AFAC case study, available on the AFAC Research Utilisation page, examines the key factors that enabled this complex research to be utilised effectively.

The researchers and end-users agree that the key success factor was their partnership approach, which was built on mutual trust and commitment to deliver practical, science-backed resources.

For further information on the research contact:
Dr Petter Nyman: nymanp@unimelb.edu.au
Dr Noreen Krusel: Noreen.krusel@afac.com.au.

For further information on the ACT trial, contact Dr Adam Leavesley: adam.leavesley@act.gov.au.