Estuaries are semi-enclosed waterbodies where freshwater from streams and rivers mixes with saltwater from the ocean. Estuaries have unique vegetation, provide important habitat for waterbirds and are nursery grounds for many fish species. DELWP has developed a condition assessment method for estuaries called the Index of Estuary Condition (IEC). The IEC is being applied to estuaries throughout Victoria to document their current condition and establish a baseline for future monitoring. This will assist in identifying investment priorities for managing estuaries.

The IEC focuses on five components of estuaries: fauna, flora, water quality, physical form (e.g. size and shape) and hydrology. Hydrology and physical form were assessed in the initial design phase of the project, using surveys and mapping. ARI has commenced a three-year fieldwork campaign, to assess the other three components at a subset of estuaries:

  • Fauna: represented by fish as they respond to environmental, ecological, physical and hydrological factors and are an important estuary component that is of interest to communities.
  • Flora: including submerged vegetation (plants on the estuary bed e.g. seagrass and macroalgae), fringing vegetation (plants around perimeter of the estuary e.g. mangroves and saltmarsh) and phytoplankton (microscopic plants in the water).
  • Water quality: includes clarity, which influences the type and extent of submerged vegetation, and dissolved oxygen saturation, which influences biological and chemical processes that are important for estuarine health. This component is being assessed in partnership with Catchment Management Authorities and citizen scientists, to draw on valuable local knowledge of our estuaries.

Powlett River estuary

Estuarine fish sampling

Barriers, like this one on the Merri River estuary in western Victoria can restrict water or biota movement

By 2019, most Victorian estuaries will have been assessed using the IEC. This project is part of an investment by the Victorian Government funded through the Water and Catchments group to improve the health of waterways and catchments. The IEC will play an important role in improving knowledge about our estuaries and sharing the importance of estuary health, and waterways in general, with the community.

Also see information on DELWP's Water and Catchments estuaries page.

For more information on assessment themes contact: (fish) (submerged vegetation)

For information on the program contact: (Water and Catchments Group)

The fact sheet below provides more details about the IEC:

Page last updated: 23/08/21