St Georges Basin

Physical characteristics

Latitude (ºS)-35.19
Longitude (ºE)150.59
Catchment area (km2)1315.8
Estuary area (km2)1,240.9
Estuary volume (ML)3215078.9
Average depth (m)45.3
Roy et al. (2001) classification5III/5/B
Entrance condition6O
  1. Derived from DECCW (2010) NSW estuaries and coastal catchments spatial database.
  2. Includes area mapped as open water (see note 1), mangrove and saltmarsh areas (Creese R. G., Glasby T. M., West G. and Gallen C. (2009) Mapping the habitats of NSW estuaries. Industry & Investment NSW Fisheries Final Report Series 113. Port Stephens, NSW, Australia.
  3. Based on areas at 0.6 m AHD (Roper T., Creese B., Scanes P., Stephens K., Williams R., Dela-Cruz J., Coade G. and Coates B. (2011) Assessing the condition of estuaries and coastal lake ecosystems in NSW. Office of Environment and Heritage, Sydney).
  4. Estimated by dividing the total volume at 0.6 m AHD by the total surface area of the estuary including mangrove areas but excluding saltmarsh (Roper et al., 2011)
  5. Estuary group: I = oceanic embayment, II = tide dominated estuary, III = wave dominated estuary, IV = intermittently closed estuary V = freshwater bodies
    Estuary type: 1 = ocean embayments, 3 = drowned valley estuary, 5 = barrier estuary, 6 = barrier lagoon, 7 = interbarrier estuary, 8 = saline coastal lagoon, 9 = small coastal creeks, 11 = brackish barrier lake. Evolution stage: A=youthful, B=intermediate, C=semi-mature, D=mature.
    (P. S. Roy, R. J. Williams, A. R. Jones, I. Yassini, P. J. Gibbs, B. Coates, R. J. West, P. R. Scanes, J. P. Hudson and S. Nichol (2001) Structure and Function of South-east Australian Estuaries. Estuarine, Coastal and Shelf Science 53, 351-384)
  6. Entrance conditions: O = open, T = trained, I = intermittent.

Tidal prism

The volume of water moving past a fixed cross section during each flood tide or ebb tide (i.e. slack water to slack water), is referred to as the tidal prism of an estuary.

The following table shows the measured tidal prism at the location specified, along with the tidal range for near the measurement site and at Sydney Harbour.

Location:     600m from the entrance on 30/5/78

Tide stateFlow
(106 m3
tidal range (m)
Sydney Harbour
tidal range (m)
Ebb flow1.30.520.8
Flood flow 1.260.641

Tidal survey

Tidal surveys measure the hydrodynamic behaviour of an estuary during a full tidal cycle. The parameters measured include velocity, water levels, salinity, temperature and pH.

The following tidal surveys have been undertaken on this estuary. A map shows the location and plots of the flows and water levels for the most comprehensive survey.

Copies of tidal survey reports are available from the Estuary Management Program

DateData collectedFigureReport
May 1978Current metering at four lines, four tideboards - velocity, discharge, cross section, temp/salinity, suspended and bed samples.1988-44.pdfMHL371
May to Sep 1992Current metering - tide levels at three locations, velocity measurements at six locations plus temp/salinity.-MHL634

Hydrographic survey

The hydrographic survey provides the depth and physical characteristics of the estuary.

The metadata associated with the survey can be found on the map sheets provided.

Map sheet number DescriptionScale    Size
10055SH1.pdfIndex plan1:10000430.3kb
10055SH2.pdfSt Georges Basin (Basin View)1:5000353.0kb
10055SH3.pdfSt Georges Basin (Sanctuary Point, Erowal Bay)1:5000425.2kb
10055SH4.pdfSussex Inlet1:5000286.2kb
10055SH5.pdfSt Georges Basin (Southeast Basin)1:5000374.6kb
9431SH1.pdfCross section locations - Sussex Inlet1:10000444.8kb
9431SH2.pdfCross sections - Sussex Inlet1:1000 H 1:200 V426.7kb
9431SH3.pdfCross sections - Sussex Inlet1:1000 H 1:200 V468.7kb
9431SH4.pdfCross sections - Sussex Inlet1:1000 H 1:200 V437.6kb
9431SH5.pdfCross sections - Sussex Inlet1:1000 H 1:200 V509.9kb
10055.txtSt Georges Basin xyz dataN/A188.0kb
Page last updated: 27 April 2012