Forests, fire and vegetation change impacts on Murray-Darling basin water resources

ABSTRACT

The Murray-Darling River system is perhaps Australia’s most important, with significant social, cultural and environmental values including 16 Ramsar listed wetlands. The MDB is home to 2.6 million people and produces about $24 billion worth in agricultural production each year (about one-third of total value for Australia). Hydrologic issues, typified by water availability and quality, have existed for many years, peaking during the Millennium drought from 1997 to 2010. Competing interests (i.e. irrigation, tourism, environmental heath), and the declining flows and water quality during droughts, led governments and water management agencies to consider the risks to water resources in the system in the early-mid 2000s. This paper reviews changes to risks associated with forest dynamics, as identified by - afforestation and bushfire – and considers new issues that have emerged since that analysis. It was found that the potential impacts of bushfire on stream flows were over-estimated in past studies, and that a planned significant afforestation expansion into agricultural and grazing land that was projected to reduce stream flows did not occur. While these two risks now do not seem likely to have significant future impacts on flows, or consequent effects on downstream users, the interaction of elevated CO₂ and increasing temperatures on vegetation functioning and subsequent hydrologic consequences at catchment scale require further research and analysis. Reduced rainfall and increased temperatures under future climate change are likely to have an impact on inputs and flows. Uncertainties in how these changes, and feedbacks between climate, drought, more frequent fire and vegetation responses, impact on system hydrology also require further investigation.

KEYWORDS:

• Streamflow
• evapotranspiration
• forests
• afforestation
• climate

Acknowledgements

The authors would like to thank Laura Matthews for help with figures and GIS analysis, and the anonymous reviewers for their work in improving the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Patrick NJ Lane

Patrick Lane is a Professor of Forest Hydrology in the School of Ecosystem and Forest Sciences, University of Melbourne. His research interests include the ecohydrology of natural and disturbed forests, streamflow dynamics and erosion processes. He has a particular interest in the effect of fire and climate variability on forest functioning and hydrology.

Richard G Benyon

Richard Benyon is a Principal Research Fellow in Forest Hydrology at the University of Melbourne. His research is focused on measuring and modelling evapotranspiration in natural, disturbed and planted forests, including effects of climate variability and change, wildfire and land use change.

Rachael H Nolan

Rachael Nolan is a Senior Research Fellow at the Hawkesbury Institute for the Environment at Western Sydney University. Her research focuses on the role of disturbances in ecosystems, in particular the effects of fire on forest ecosystem services.

Rod J Keenan

Rodney Keenan is Professor and Chair of Forest and Ecosystem Sciences at the University of Melbourne. He has research interests in sustainable forest management, forests and climate change, ecosystem services and forest policy.

Lu Zhang

Lu Zhang is an Honorary Fellow with CSIRO Environment. His research interests include ecohydrology, evapotranspiration, impacts of vegetation on catchment water balance, and ecosystem response to climate change.