eReefs hydrodynamic model - Freshwater exposure (AIMS, Source: CSIRO)

This generated data set contains exposure products derived from the eReefs CSIRO hydrodynamic model v2.0 (https://research.csiro.au/ereefs) outputs at both 1km and 4km resolution, generated by the AIMS eReefs Platform (https://ereefs.aims.gov.au/ereefs-aims). These exposure products are derived from the original hourly model outputs available via the National Computing Infrastructure (NCI) (https://dapds00.nci.org.au/thredds/catalogs/fx3/catalog.html), and have been re-gridded from the original curvilinear grid used by the eReefs model into a regular grid so that the data files can be easily loaded into standard GIS software. These products are made available via a THREDDS server (https://thredds.ereefs.aims.gov.au/thredds/) in NetCDF format. For more information about the eReefs hydrodynamic modelling see https://research.csiro.au/ereefs/models/models-about/models-hydrodynamics/.

This dataset contains the following exposure products:



FRESH WATER EXPOSURE
The freshwater exposure products calculate the level of exposure to salinity levels below a threshold over a calendar month. The standard thresholds used in the freshwater exposure products generated by the AIMS eReefs Platform are 26 and 28 PSU (refer to the attributes attached to the variables in the NetCDF files to confirm). These were chosen as different species have different tolerances to freshwater exposure, and the most appropriate level is not currently known.


Method:

The freshwater exposure is calculated from the sum of the daily average salinity below the exposure threshold. Salinity levels above the threshold don't contribute at all to the exposure. Salinity levels below the threshold contribute in proportion to the amount below the threshold. As a result with a threshold of 28 PSU and an exposure to 22 PSU for 3 days the freshwater exposure would be (28-22)3 = 18 PSU days. The same exposure at 25 PSU would take 6 days (28-25)6 = 18 PSU days. This method of calculating exposure is conceptually very similar to temperature exposure measured in Degree Heating Weeks, where the higher the temperature is above the typical maximum summer temperature the faster the heat stress occurs. For freshwater exposure the stress occurs when the salinity drops below the threshold value. The lower the salinity the faster the exposure accumulates. More research is needed to determine if this is the best method for estimating stress from freshwater.

A more detailed description of the processing, especially exposure calculations and regridding, is available in the "Technical Guide to Derived Products from CSIRO eReefs Models" document (https://nextcloud.eatlas.org.au/apps/sharealias/a/aims-ereefs-platform-technical-guide-to-derived-products-from-csiro-ereefs-models-pdf ).

Data Dictionary:

The variables found in the freshwater exposure products document the threshold used to calculate that variable. For example:



fresh_water_exposure_29p5 : threshold = 29.5

fresh_water_exposure_28 : threshold = 28.0

fresh_water_exposure_26 : threshold = 26.0


Depths:

Depths at 1km resolution: -2.35m

Depths are 4km resolution: -1.5m

Limitations:

This dataset is based on a spatial and temporal model and as such is an estimate of the environmental conditions. It is not based on in-water measurements, and thus will have a spatially varying level of error in the modelled values. It is important to consider if the model results are fit for the intended purpose.

Change Log:
2025-10-17: Updated title to align with other eReefs datasets, changing the title from the original 'eReefs AIMS-CSIRO Exposure of hydrodynamic model outputs'. Added project team members with ROR, and ORCIDs, and minted a DOI for the record.

Organization: Australian Ocean Data Network