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 developed a condition assessment method for estuaries called the Index of Estuary Condition (IEC). The IEC was applied to estuaries throughout Victoria to document their current condition and establish a baseline for future assessments. This is assisting in guiding the management of Victoria’s estuaries.

The IEC focuses on five components of estuaries: physical form, hydrology, water quality, flora and fish. ARI was involved in the fish, flora and water quality themes:

  • Fish - used as representative of the broader community of estuary animals, as fish respond to environmental, ecological, physical and hydrological factors and are an important estuary component that is of broad interest to communities.
  • Flora - includes the structure of vegetation along shorelines and whether submerged vegetation is predominantly seagrass or macroalgae.
  • Water quality - includes clarity, which influences the type and extent of submerged vegetation, and chlorophyll-a concentration, which is indicative of primary production that is responsive to nutrient inputs and is important for estuarine health. This component was 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

The first state-wide IEC assessment for Victorian estuaries was delivered in 2021. This project was 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 plays an important role in improving knowledge about our estuaries and sharing the importance of estuary health, and waterways in general, with the community.

You can find more details about the project on DELWP's Water and Catchments estuaries page.

For more information on the IEC assessment contact: (Water and Catchments Group)

Page last updated: 06/12/21