Victorian index of estuary condition : recommended themes and measures

Deakin University was engaged by the Department of Sustainability and Environment to develop an Index of Estuary Condition (IEC) for evaluating the environmental condition of Victorian estuaries. The Index will ultimately complement the existing Index of Stream Condition (ISC) by providing a consistent statewide assessment of the environmental condition of estuaries. This will better enable:

• Estuarine condition to be reported at regional, state and national levels.

• Prioritisation of resource allocation.

• Strategic evaluation of management interventions in estuaries.

Workshops involving participants with expertise in a variety of disciplines were convened to integrate learnings from assessment programs currently being developed interstate and overseas. This report synthesises and builds on the output from those workshops which:

• Identified key components (themes) of estuaries that contribute to estuarine condition.

• Contributed to development of a broad conceptual model for Victorian estuaries

• Identified possible measures of each theme

In keeping with the sub-indices of the ISC, six themes were identified for use in the IEC: Physical form, Hydrology, Water quality, Sediment, Flora and Fauna. Several measures within each theme are recommended to assess estuary condition.

Implementation of particular measures in the IEC partly depends on the investment required to both collect and interpret the required data. With regard to data collection, each measure was assessed according to whether there is an established sampling procedure, how frequently data need to be collected and the level of expertise required for collection and processing. For interpreting the data, measures were scored on whether baseline condition is established and whether descriptions and scores are developed which reflect the extent of deviation from that condition. These scores were used to indicate which measures are feasible to implement immediately and which require further investigation.

A trial of the recommended IEC measures in a selection of estuaries is recommended as it would provide an opportunity to test the measures and their suitability for application statewide. It is suggested that the trial is conducted in estuaries subject to various levels of threats within each of the four estuary classes described by Barton et al. (2008)