Coastal Eutrophication Risk Assessment Tool

The Coastal Eutrophication Risk Assessment Tool (CERAT) is used to better understand and predict the relationship between land use in catchments and its impact on estuaries and coastal lakes like Lake Illawarra.

Lake IllawarraScientists from the former Office of Environment and Heritage (OEH) have developed this tool to help identify and prioritise land use planning decisions to protect and preserve the health of estuaries in NSW.

CERAT consists of:

  • a water quality database
  • contextual spatial information for the catchment or estuary
  • a coupled series of catchment and estuary models for the main (184) estuaries in NSW.

The models can be used by non-technical users and are built from readily available and/or routinely collected monitoring data and information.

The catchment models provide estimates of the amounts of nutrients and sediments exported from land-based activities, such as urban development, deforestation and agriculture. The estuary models assess the potential impact of these exports on the water quality, micro-algal biomass and seagrass abundance in the estuary.


Eutrophication, or more precisely hypertrophication, is the enrichment of a water body with nutrients, usually with an excess amount of nutrients. This process induces growth of plants and algae and due to the biomass load, may result in oxygen depletion of the water body. One example is the "bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is almost always induced by the discharge of phosphate-containing detergents, fertilizers, or sewage, into an aquatic system.

~ Schindler, David and Vallentyne, John R. (2004) Over fertilization of the World's Freshwaters and Estuaries, University of Alberta Press, p. 1, ISBN 0-88864-484-1


The outputs from the models can be used to identify estuaries which are most vulnerable to impacts from catchment land use change and therefore at most risk from eutrophication. They provide a systematic and scientific basis for prioritising resources for monitoring and mitigating pollutant exports from the catchment.

CERAT is available on the OzCoasts website.

The work was funded by the Natural Heritage Trust, the National Action Plan for Salinity & Water Quality and OEH.