Environmental water needs for the Mitchell River

River catchments, particularly the Mitchell River catchment, of the Gulf of Carpentaria are home to many important freshwater assets, such as significant commercial and recreational fisheries, threatened species, and wetlands of national significance. With considerable interest in agricultural expansion in the Gulf, there’s concern these assets may be impacted by intensive development.

These assets depend greatly on the linkages between rivers, floodplains and estuaries. However, our current ability to predict the consequences of future development on these linkages is limited. There are also significant gaps in our understanding of environment flow requirements, such as the quantity and timing of water flows needed to trigger the migration of key aquatic species

This research will improve our understanding of the critical flow needs to sustain freshwater ecosystems in the Mitchell River catchment. In particular, the project aims to predict the impacts of future development on important ecosystem linkages between the river and its floodplain wetlands, and to better understand other potential risks associated with changes to flow regimes. This information is vital to help inform decision makers about water allocation that both enables agricultural development and protects environmental assets.

Component 1: Threat assessment of ecological assets in the Mitchell River
An initial desktop threat assessment will generate information about key ecological assets, their critical links to flow, and the likely consequences of development in the Mitchell River.

Component 2: Implications of water resource development on flood flows and ecosystem productivity in the Mitchell River
A river model will be developed for the Mitchell River, including the analysis of floodplain inundation. The researchers will use remote sensing to capture current flood inundation patterns and these will be combined with modelled inundation patterns that incorporate the impact of development scenarios. This model will be used to predict the likely effect of development scenarios on floodplain wetlands in the river, before estimating the impacts of these changes on aquatic primary production.

Component 3: Critical flow needs for ecological assets in the Mitchell River
The initial threat assessment in the Mitchell River (Component 1) and potential scenarios for development (Component 2) will be used to identify key gaps in understanding of important flow requirements for ecological assets within the river. Additional analysis of remote sensing information and field surveys will be undertaken to support this process. Target sampling of important species that have been poorly studied in the lower Mitchell River will also be undertaken to determine how much they depend on river, floodplain and estuarine sources of producing. This will be undertaken using a combination of chemical tracing methods. The researchers will also use archived otoliths (ear bones) from barramundi in the Mitchell River to determine how flood flows influence movement and growth.

  • Identifying and mapping key ‘hotspots’ of freshwater primary production within the Mitchell River floodplain associated with flow-driven flooding as high priority areas for protection;
  • Improving our understanding of the importance of these high priority areas for sustaining fish populations, birds, turtles, crocodiles and other aquatic species;
  • Identifying other flow-dependent ecological assets in the Mitchell River and how they are likely to be impacted by water resource development; and
  • Increasing confidence in water planning for river catchments in the Gulf thanks to an improved understanding of ecological assets and their critical links to flow.

The research will be undertaken within the Mitchell River catchment, with a focus on the floodplain and other key ecological assets in-stream.

Mitchell River catchment map

 

This project is being led by Professor Stuart Bunn from Griffith University.

Professor Bunn will be supported by researchers from Griffith University, CSIRO, Queensland Department of Science, Information Technology & Innovation, Queensland Department of Agriculture & Fisheries, and Charles Darwin University.

Contact
Stuart Bunn, Griffith University
E: s.bunn@griffith.edu.au
T: (07) 373 57407