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.

This project will:

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

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
Researchers will use river models to predict the effect of development scenarios on floods, and combine modelled floodplain inundation patterns with inundation patterns captured from satellite images to analyse the ‘connectivity’ of the floodplain. This understanding of how rising floodwaters connect low areas across the floodplain, and of how long these connections last and waterholes persist in different places, will help highlight the effects of changes in flow on floodplain wetlands. Without such connectivity, floodplains can’t provide important resources such as food back to the river, even if particular wetlands produce abundant resources. The timing, duration and frequency of floodplain connections will likely change with changes in river flow and therefore potentially impact habitat, food and/or access for fish, birds and other species.

Component 3: Critical flow needs for ecological assets in the Mitchell River
Researchers will map important aquatic refugia, floodplain wetland vegetation and algal production using remote sensing and field surveys to determine the impacts of changes to flows on the distributions and quality of habitat and food sources. The team will sample important species to determine how much each depends on river, floodplain and estuarine sources of food production. Otoliths (fish ear bones) have been extracted from multiple species and will be used to determine how flood flows influence their movement and growth. Researchers will then use this understanding of species food, habitat and movement needs to identify their river and floodplain flow needs. They will combine this with the threat assessment (C1) and floodplain connectivity modelling (C2) to assess the impact of potential developments that alter flows and disrupt connectivity through water extraction and infrastructure in channels or across floodplains.

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 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
[email protected]
(07) 373 57407

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  • Mitchell River, photo Peter Negus
  • Mitchell River field work, photo Peter Negus.
  • Mitchell River field work, photo Peter Negus.
  • Mitchell River field work, photo Peter Negus.
  • Mitchell River during the dry season, photo Peter Negus.
  • Mitchell River bed during the dry season, photo Peter Negus.
  • Mitchell River field work, photo Peter Negus.
  • Field work on the Mitchell River, photo Kate Hodges.
  • Field work on the Mitchell River, photo Kate Hodges.
  • Field work on the Mitchell River, photo Kate Hodges.
  • Coal grunter (Hephaestus carbo), photo Kate Hodges
  • Field work on the Mitchell River, photo Kate Hodges.
  • Mitchell River, photo Kate Hodges.
  • Fieldwork on the Mitchell River, photo Kate Hodges