Arundel et al. (2009), after extensive consultation and expert panel workshops, recommended six themes (physical form, hydrology, water quality, sediment, flora, and fauna), and 18 measures for a Victorian Index of Estuary... [ view full abstract ]
Arundel et al. (2009), after extensive consultation and expert panel workshops, recommended six themes (physical form, hydrology, water quality, sediment, flora, and fauna), and 18 measures for a Victorian Index of Estuary Condition (IEC). All measures were conceptually linked to estuary condition. The overall IEC score is used to rate an estuary using categorical condition bands (excellent, good, moderate, poor, and very poor), and was developed for the spatial comparisons of estuary condition across the state. These assessments are planned to be repeated every eight years for prioritisation and resource allocation for natural resource management.
The IEC implementation trial tested if the measure methods from Arundel et al. (2009) were applicable state-wide. It also defined baselines, scoring methods and score confidence metrics using existing and new data. This represents over four years of effort in collating and interpreting data, three intensive summer field seasons across the Victorian coastline, and a number of measure-specific pilot studies.
This presentation outlines the approach used in determining baselines, scoring and score confidence, aggregation of scores within and between physical themes, and presents some insights into the current condition of Victorian estuaries. One hundred and one estuary mouths, current and natural heads, and fluvial and estuarine catchments have been spatially defined. Field sampling in 55 estuaries, and their subestuaries, allowed the definition of the upper, middle and lower estuarine zones, as well as the collection of depositional sediment size and water depths. It also allowed the comparison of water clarity in 55; surface dissolved oxygen in 51; diurnal oxygen sags in 45; bank erosion in 48; microphytobenthos biomass in 41; and phytoplankton biomass in 44 estuaries. Data collected and collated as part of the trial allow the comparison of modification of estuary extent and freshwater flow in 101, sediment load in 56, and marine exchange in 85 estuaries.
Thirteen measures across the six themes have been recommended for the first formal IEC program. At least four themes out of the possible six themes are needed to be able to score an estuary, including water quality and at least one biological theme of flora or fauna.
