Fires and hydrology

This study examined the eco-hydrology of mixed-species eucalypt forests as they regenerate after crown-removing fires, such as the 2009 Black Saturday fires. The investigation was based on broad management questions: How much water is used by trees after fire? How much water goes into catchments? Is the quality of this water fit for use in towns and cities?

The research was conducted by the University of Sydney’s Dr Tina Bell and Dr Tarryn Turnbull, who found that the water use by vegetation in mixed-species eucalypt forests did not increase markedly during the recovery phase following intense fire.

This is a significant finding, as it means it is unlikely that water yields from mixed-species catchments will be as strongly affected by fire as water yields from forests comprised of Ash-type eucalypts, where much previous research has been conducted.

A key difference between the mixed-species forests and the Ash-type forests is that the trees in mixed-species forests mostly resprout after fire, while the Ash-type forests are killed and regrow from seed.

The findings from this project can be used by catchment land planners and water supply authorities to find optimal strategies for simultaneously managing fire and ensuring water supply continuity. The results are directly applicable to the mixed-species catchments in south eastern Australia.

Outside of south eastern Australia, catchment managers may be able to build on this work and have the vegetation water use models validated for new ecosystems. The work may also be useful at a strategic level to inform water policy.

The effect of bushfire on Sydney’s water catchments was investigated in a PhD study from Jessica Heath (University of Sydney). Her work showed that the pre‐bushfire models used had predicted the post‐bushfire models well, and that bushfire had no obvious effect on water yield within the Sydney drinking water supply catchments.