Project overview

The model results presented here were developed as part of Theme 7b (Estuarine Health) of the National Land and Water Resources Audit. The Estuarine Audit is primarily concerned with an assessment of the current environmental health of Australia's estuaries, and has adopted a pressure-state-response framework in making this assessment. The modelling component presented here focuses on the relationships between pressures, anthropogenic and natural, and estuarine state, as reflected in a range of model indicators. The results may be used both to fill in gaps in pressures or indicators in the data-based assessment, and perhaps more importantly to understand the ways in which estuaries respond to different pressures, and hence guide thinking about management responses. We emphasize however that the generic models presented here are not intended and should not be used as a substitute for local calibrated models in making management decisions in specific estuaries.

Not all pressure and state indicators used in the Audit are captured in these models. For the most part, the models deal with pressures related to physical and chemical forcing (runoff, flushing, nutrient and sediment loads), and predict indicators related to water quality (nutrients, dissolved oxygen, light attenuation) and primary producers (phytoplankton, benthic microalgae, seagrass, macroalgae).

The models used here build on experience gained in a number of major environmental studies in Australian waters, and on general scientific and process understanding published in the national and international scientific literature. The Audit represents a first attempt to translate and extrapolate this process understanding, encapsulated in models developed through a relatively small number of case studies, to conclusions about the broad range of Australian estuaries. Bearing in mind that it is a first attempt, the user should treat the results with a healthy degree of caution. For example, the models have largely been developed and calibrated in temperate and sub-tropical estuaries. There have been very few studies of Australia's tropical macrotidal estuaries, and model predictions for those estuaries may be less reliable.

While this first attempt involves considerable extrapolation from our current knowledge base, the Audit itself will provide data to assess model performance. We anticipate that the current project will prove the first step in an ongoing cycle of model prediction, observation, and model refinement.