Critical water needs to sustain freshwater ecosystems and aquatic biodiversity in Queensland’s Mitchell River

Abstract

Critical water needs to sustain freshwater ecosystems and aquatic biodiversity in Queensland’s Mitchell River

The Australian Government has identified water-resource development in the north of Australia as a priority for the coming years and Queensland’s Mitchell River is a focus of this interest. The Queensland Government currently regulates small amounts of extraction from the Mitchell River meaning that the flow regime is largely unregulated. In its current condition, the catchment supports existing water users, including Traditional Owners, and significant ecological assets, including wetlands of national significance, threatened species, traditional harvests, and commercial and recreational fisheries. Information is needed on the water needs of freshwater ecosystems and their associated biodiversity to guide decision-making around water planning and development.
This project examined the links between freshwater flow and floodplain inundation, aquatic plant biomass accumulation, floodplain subsidies to freshwater food webs, fish movement and fisheries production. This project had five major objectives to understand the flow requirements of freshwater assets:
1. Identify the dependence of floodplain inundation and aquatic plant biomass accumulation on river flow
2. Map key ‘hotspots’ of freshwater primary productivity within the floodplain
3. Quantify riverine and floodplain connectivity to assess the likely impact of varying wet seasons and water-resource development on aquatic food webs, and the movement of fish between river channels and floodplain wetlands
4. Quantify the importance of river flows to estuaries by examining the flow dependence of barramundi growth, population dynamics and habitat use
5. Assess the implications of flow alteration on freshwater ecological communities, including movement of fish throughout the catchment.